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Dried Plums and Their Products: Composition and Health Effects-An Updated Review

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This paper describes composition of dried plums and their products (prune juice and dried plum powder) with special attention to possibly bioactive compounds. Dried plums contain significant amounts of sorbitol, quinic acid, chlorogenic acids, vitamin K1, boron, copper, and potassium. Synergistic action of these and other compounds, which are also present in dried plums in less conspicuous amounts, may have beneficial health effects when dried plums are regularly consumed. Snacking on dried plums may increase satiety and reduce the subsequent intake of food, helping to control obesity, diabetes, and related cardiovascular diseases. Despite their sweet taste, dried plums do not cause large postprandial rise in blood glucose and insulin. Direct effects in the gastrointestinal tract include prevention of constipation and possibly colon cancer. The characteristic phenolic compounds and their metabolites may also act as antibacterial agents in both gastrointestinal and urinary tracts. The indirect salutary effects on bone turnover are supported by numerous laboratory studies with animals and cell cultures. Further investigation of phenolic compounds in dried plums, particularly of high molecular weight polymers, their metabolism and biological actions, alone and in synergy with other dried plum constituents, is necessary to elucidate the observed health effects and to indicate other benefits.
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Critical Reviews in Food Science and Nutrition, 53:1277–1302 (2013)
Copyright C
Taylor and Francis Group, LLC
ISSN: 1040-8398 / 1549-7852 online
DOI: 10.1080/10408398.2011.563880
Dried Plums and Their Products:
Composition and Health Effects–
An Updated Review
M. STACEWICZ-SAPUNTZAKIS
Department of Kinesiology and Nutrition, University of Illinois at Chicago, Chicago, Illinois, USA
This paper describes composition of dried plums and their products (prune juice and dried plum powder) with special
attention to possibly bioactive compounds. Dried plums contain significant amounts of sorbitol, quinic acid, chlorogenic
acids, vitamin K1, boron, copper, and potassium. Synergistic action of these and other compounds, which are also present
in dried plums in less conspicuous amounts, may have beneficial health effects when dried plums are regularly consumed.
Snacking on dried plums may increase satiety and reduce the subsequent intake of food, helping to control obesity, diabetes,
and related cardiovascular diseases. Despite their sweet taste, dried plums do not cause large postprandial rise in blood
glucose and insulin. Direct effects in the gastrointestinal tract include prevention of constipation and possibly colon cancer.
The characteristic phenolic compounds and their metabolites may also act as antibacterial agents in both gastrointestinal and
urinary tracts. The indirect salutary effects on bone turnover are supported by numerous laboratory studies with animals and
cell cultures. Further investigation of phenolic compounds in dried plums, particularly of high molecular weight polymers,
their metabolism and biological actions, alone and in synergy with other dried plum constituents, is necessary to elucidate
the observed health effects and to indicate other benefits.
Keywords Prunes, prune juice, sorbitol, chlorogenic acids, quinic acid, laxation
INTRODUCTION
Prunes are dried plums prepared from prune-making varieties
of Prunus domestica L., such as French plums cv d’Agen, Italian
prune plums cv Sugar, and cv President, and many European and
Middle East plum cultivars. Unfortunately, there are instances
in the literature where the authors refer to “prunes” when they
mean fresh plums of unknown species and variety, probably be-
cause of the incorrect translation of the Latin name for the genus
Prunus into English. It is often in case of the Japanese oriental
plum (Prunus salicina Lindl.), the species which includes many
varieties of plums grown now all over the world (popular va-
rieties such as Red Beauty, Black Beauty, Santa Rosa, Queen
Rosa, Cassleman, Black Amber, Angelino, Simka, Laroda, El
Dorado, Friar, and Kelsey). However, Chinese, Japanese, and
Korean authors also use terms “prune” or “plum” interchange-
ably for the ume plum (Prunus mume), which is genetically
closer to apricots than to plums, and is sometimes called an
Asian apricot. In China and Japan these fruits are often pickled
Supported by a grant from California Dried Plum Board, Sacramento, CA.
Address correspondence to M. Stacewicz-Sapuntzakis, Department of Kine-
siology and Nutrition, University of Illinois at Chicago, 1919 West Taylor St.,
Chicago, IL 60612, USA. E-mail: msapuntz@uic.edu
or dried, but the final product is very different from the dried Cal-
ifornia plum. On the other hand, there are many plum varieties
in Europe and Middle East that belong to the Prunus domestica
L. species, which are not used for production of dried plums.
The purpose of this paper is to provide a critical review of
recent studies (2000–2010) that link the consumption of dried
plums/prunes and their products to health effects. The com-
position section of the report compiles the available data on
dried plums and their products. The discussion of physiological
effects includes also studies of fresh plums, sometimes not of
prune-making varieties, and their products, because certain con-
stituents are the same, albeit in different proportions. In every
case the species’ name and variety are clearly stated, if known,
to avoid misunderstanding.
COMPOSITION OF DRIED PLUMS AND
THEIR PRODUCTS
Carbohydrates
The previous review (Stacewicz-Sapuntzakis et al., 2001)
organized then available data from various sources, among them
food composition tables from the US Department of Agriculture
1277
1278 M. STACEWICZ-SAPUNTZAKIS
Tab le 1 USDA and NDS-R composition tables
Dried plums Prune juice
SR 25 SR 25 NDS-R SR 25 SR 25 NDS-R
Serving (g)a100 42 47.5 100 256 256
Energy (kcal) 240 101 114 71 182 182
Total carbohydrate (g) 63.88 30.34 44.67
Available carbohydrate (g) 26.97 42.11
Total sugars (g) 38.13 16.01 18.11 16.45 42.11 34.82
Glucose (g) 25.46 12.09 14.08
Fructose (g) 12.45 5.91 20.22
Sucrose (g) 0.15 0.07 0.51
Starch 5.11 2.43
Total dietary fiber (g) 7.1 3.0 3.37 1 2.6 2.56
Insoluble fiber (g) 1.51 1.28
Soluble fiber (g) 1.87 1.28
Pectin (g) 1.09
Sorbitol (g) 12b5.70 15.38
Protein (g) 2.18 0.92 1.04 0.61 1.56 1.56
Fat (g) 0.38 0.16 0.18 0.03 0.08 0.08
Moisture (g) 30.92 12.99 14.69 81.24 207.97 207.97
Ca (mg) 43 18 20 12 31 31
K (mg) 732 307 348 276 707 707
Fe (mg) 0.93 0.39 0.44 1.18 3.02 3.02
Mg (mg) 41 17 19 14 36 36
P (mg) 69 29 33 25 64 64
Cu (mg) 0.281 0.118 0.13 0.068 0.174 0.17
Mn (mg) 0.299 0.126 0.14 0.151 0.387 0.39
Se (μg) 0.3 0.1 0.14 0.6 1.5 1.54
Zn (mg) 0.44 0.18 0.21 0.21 0.54 0.54
Vitamin A (μgRAE) 39 16 19 0 0
Beta-carotene (μg) 394 165 187 2 5 5
Alpha-carotene (μg) 57 24 27 0 0
Beta-cryptoxanthin (μg) 93 39 44 0 0
Lutein +zeaxanthin (μg) 148 62 70 40 102 102
Vitamin C (mg) 0.6 0.3 0.29 4.1 10.5 10.5
Vitamin E (mg a-tocopherol) 0.43 0.18 0.18 0.12 0.31 0.31
Vitamin K1 (μg) 59.5 25 28.26 3.4 8.7 8.7
Thiamin (B1) (mg) 0.051 0.021 0.02 0.016 0.041 0.04
Riboflavin (B2) (mg) 0.186 0.078 0.09 0.07 0.179 0.18
Niacin (mg) 1.882 0.79 0.89 0.785 2.01 2.01
Panthotenic acid (mg) 0.422 0.177 0.2 0.107 0.274 0.27
Vitamin B6 (mg) 0.205 0.086 0.1 0.218 0.558 0.56
Folate (μg) 4 2 2 0 0 0
Choline (mg) 10.1 4.2 4.8 2.7 6.9 7.17
Oxalic acid (mg) 4.37 8.7
Notes: aA standard serving of dried plums is 42 g, but 100 g were used in the majority of human trials.
bSorbitol content is from USDA (1987) Sugar Content of Selected Foods.
(USDA) and European sources. During the last decade, USDA
periodically updated their food composition data, improving
reliability and including more nutrients. Table 1 provides the
nutritional content of dried plums (100 g) and of prune juice
(256 g, or 1 cup). These amounts probably represent the upper
range of intake per day, since larger doses may not be feasible
in intervention trials for adult subjects. The standard serving of
dried plums is 40 g in food industry labeling, 42 g (five dried
plums) in the USDA database, 47.5 g in the Nutrition Data
System for Research (NDS-R, 2008; widely used by nutritionists
to calculate dietary nutrient intake). All three sources consider
one cup of prune juice (240 mL) to be a standard serving.
Available carbohydrates (sugars and starch) provide nearly
all the energy from dried plums. In the latest USDA Standard
Reference Release SR 2 (USDA, 2012) sugars are represented
mostly by glucose and fructose (25.5 g and 12.5 g/100 g, respec-
tively), with traces of sucrose and maltose. The total amount of
sugars in SR 25 does not include sorbitol. Current SR 25 does
not list sugar alcohols, but an older USDA publication (USDA,
1987) reported 12 g of sorbitol/100 g of dried plums.
The US Department of Agriculture does not provide data for
the individual sugars in prune juice. The data from 1987 appear
to be incorrect, because the proportion of glucose and fructose
in prune juice is reversed (14.1 g glucose and 20.2 g fructose
HEALTH EFFECTS OF DRIED PLUMS AND THEIR PRODUCTS 1279
Tab le 2 Carbohydrates in fresh prune-making plums, dried plums, and prune
juice
Component Fresh prune Prune juice Dried plums
(g/100 g FW) plums
Total dietary fiber 2.71.19.1
Oligosaccharides 0.60.11.4
Glucose 15.04.9 20.6
Fructose 9.23.0 13.1
Sucrose 0.30.10.6
Sorbitol 5.82.89.1
Inositol 1.50.71.8
Adapted from Dikeman et al. (2004) and Bauer and Fahey (2004).
per 256 g, or 8 oz) compared with dried plums. However, these
values are still used by the NDS-R program. The total amount
of sugars in prune juice, reported in SR 25 (USDA, 2012), was
not directly measured but calculated by difference after sub-
tracting water, ash, lipid, protein, and total fiber content, and
therefore it includes sorbitol. NDS-R uses the value of 15.6 g
sorbitol per cup as the reported average content from the study
of various kinds of prune juice (with pulp, no pulp, and recon-
stituted; van Gorsel et al., 1992; Stacewicz-Sapuntzakis et al.,
2001).
An extensive study of carbohydrate composition examined
18 plum/prune products, and reported results on the basis of dry
weight (DW) (Bauer and Fahey, 2004; Dikeman et al., 2004).
The study included prune juice, dried plum powder, and three
kinds of dried plums (pitted prunes, prune 52/26 with pits, and
undersized prunes). Table 2 is adapted from this study, but the
values are recalculated on the basis of fresh weight (FW, as
consumed, edible portion) and the results for three kinds of dried
plums are averaged. The data for glucose and fructose in dried
plums are in good agreement with the USDA table, but the total
content of sugars in prune juice is only half of that listed in SR
25 (USDA, 2010). The ratio of glucose to fructose in prune juice
is the same as in dried plums. Although sorbitol was measured
in the above-described study (Dikeman et al., 2004), the authors
did not report it for individual prune products. However, the
study report (Bauer and Fahey, 2004) provided sorbitol content
of dried plums (average 9.1 g/100 g FW), and that of prune
juice (7.1 g/cup). Very little oligosaccharides were found in
dried plums (Table 2).
Dried plums have a relatively high content of inositol
(1.8 g/100 g), while prune juice contains the same amount per
cup (Table 2). In a survey of inositol content in common foods
(Clements and Darnell, 1980), dried plums were reported to have
470-mg inositol/100 g and prune juice had 666 mg/cup, while
fresh red and yellow plums contained insignificant amounts.
Dried plums contain 7.1 g of total dietary fiber per 100 g,
while prune juice has 2.56 g per cup (256 g), according to
USDA tables, which do not list separately soluble and insoluble
fiber. A large serving of dried plums (100 g) delivers about 20%
of the adequate intake (AI) of dietary fiber recommended for
adults (25 g for women, 38 g for men; Institute of Medicine,
2005). Table 2 provides data for total dietary fiber from Dikeman
et al.’ (2004) study, which are slightly higher, 2.8 g/cup for
prune juice and 9.1 g/100 g average for dried plums. This result
is in good agreement with another study from France, which
obtained an average of 9.2 g total dietary fiber per 100 g in dried
plums, with 5.3 g of soluble and 3.9 g of insoluble fiber (Fatimi
et al., 2007). The proportion of galacturonic acid (42%) in the
soluble fiber indicated a predominance of pectins, and 26% of
glucose in the insoluble fiber pointed toward cellulose as the
main component. A review of nutritive values of fresh plums
(Walkowiak-Tomczak, 2008a), which includes prune-making
and other plum varieties, lists the following FW content ranges:
86–88% water, 0.8–1.0% pectin, and 1.3–2.4% total dietary
fiber. Pectins were also measured in 12 varieties of P. domestica
plums grown in one location in Czech Republic (Rop et al.,
2009). The pectin content was very high, 2.2–3.5 g/100 g FW.
The authors did not report moisture content of these plums. The
average moisture content of prune-making plums from other
studies is 80% (Somogyi, 2005). Stanley plums from Turkey
contained 89% moisture (Ertekin et al., 2006), but fresh d’Agen
plums from California in Dikeman et al.’ (2004) study had only
57% water.
Minerals
Table 1 lists the updated values for minerals in dried plums
and prune juice as reported in the SR 25 (USDA, 2012). Table 3
shows the proportion of the recommended dietary allowance
(RDA) or adequate intake, which may be satisfied by a large
serving of dried plums (100 g) or a cup of prune juice. The ref-
erence values in Table 3 are the highest-recommended values for
adults, except for pregnant and lactating women, by the Food and
Nutrition Board (Institute of Medicine, 1997, 1998, 2000, 2001,
2005). Dried plums (100 g serving) are a good source of copper
(31% RDA), potassium (16% AI), manganese (13% AI), and
magnesium (10% RDA). Prune juice (256 g) is similarly high in
copper (19% RDA), manganese (17% AI), and potassium (15%
AI), but also in iron (17% RDA). The relatively high content
of iron in prune juice is difficult to reconcile with that of dried
plums. Considering that the majority of the US population falls
short on the nutrient needs for many minerals (97%, 70%, and
55% of population have inadequate intake of potassium, cal-
cium, and magnesium, respectively; Nicklas et al., 2009), dried
plums and their products may make a valuable contribution to
meet nutritional recommendations. Although the dietary refer-
ence intakes have not been established for boron, the mean intake
of boron in the US population is 1.15 mg/day and the highest
intake from food is 3 mg/day (Institute of Medicine, 2001). A
large serving of dried plums contains 2.2 mg of boron, while a
cup of prune juice may deliver 0.6 mg of boron (Anderson et al.,
1994).
The amount of minerals in dried plums and their products
is directly related to the mineral content of fresh prune-making
plums, which may be quite variable and depends on cultivar,
soil, growing conditions, and agricultural practices (such as
1280 M. STACEWICZ-SAPUNTZAKIS
Tab le 3 Percentage of dietary reference intakes (DRI) per serving
Nutrient New DRI % in dried plums % in prune juice
Serving (g) 100 256
Available carbohydrate (g) 130 33.232.4
Total dietary fiber (g) 38 18.76.8
Ca (mg) 1300 3.32.4
K (mg) 4700 15.615.0
Fe (mg) 18 5.216.8
Mg (mg) 420 9.88.6
P (mg) 1250 5.55.1
Cu (mg) 0.931.219.3
Mn (mg) 2.313.016.8
Se (μg) 55 0.52.7
Zn (mg) 11 4.04.9
Vitamin A (RAE) 900 4.30.0
Vitamin C (mg) 90 0.711.7
Vitamin E (mg α-tocopherol) 15 2.92.1
Vitamin K1 (μg) 120 49.67.3
Thiamin (B1) (mg) 1.24.33.4
Riboflavin (B2) (mg) 1.314.313.8
Niacin (mg) 16 11.812.6
Pantothenic acid (mg) 5 8.45.5
Vitamin B6 (mg) 1.712.132.8
Foliate (μg) 400 1.00.0
Choline (mg) 550 1.81.3
Note: DRI – highest RDA or adequate intake (AI), except in pregnancy or
lactation.
fertilizers). Table 4 shows the mineral content of fresh plums
from various studies. USDA SR 25 values are for unspecified
varieties of plums, and the range of values quoted in the Polish
review (Walkowiak-Tomczak, 2008a) also includes unspecified
varieties, possibly of P. domestica and P. salicina. Czech plum
data (Rop et al., 2009) are for 12 local varieties of P. domestica
(including prune-making plums). Stanley plums were grown
in Turkey, where they are used for production of dried plums
(Ertekin et al., 2006). Their content of calcium, copper, man-
ganese, and zinc was much higher than the average values listed
for the unspecified fresh plums in USDA SR 25.
Tab le 4 Mineral content of fresh plums from various studies (mg/100 g FW)
Mineral USDA Review, 2009 Czech plums Stanley plums
Ca 4 6–45 7.1–11.4 13
K 104 120–208 160–398 127
Fe 0.11 2.3
Mg 5.0 4.0–8.0 6.4–11.6 2.5
P 11 20–37 9.6
Cu 0.038 1.5
Mn 0.034 0.3
Zn 0.07 1.2
Note: USDA data are from SR 25 (unspecified plum varieties).
Review, from Walkowiak-Tomczak (2008a), unspecified plum varieties.
Czech plum data are from Rop (2009), 12 varieties (P. domestica).
Stanley plum data are adapted from Ertekin et al. (2006).
Vitamins
Vitamin values were also updated in the latest USDA SR
25 (Table 1). Table 3 indicates that dried plums are an excellent
source of vitamin K1, phylloquinone, since 100 g serving covers
50% of the adequate intake. Dried plums also contain significant
amounts of riboflavin (14% RDA), niacin (12% RDA), and
vitamin B6(12% RDA) in a 100 g serving. A cup of prune
juice (256 g) delivers similar amounts of riboflavin (14% RDA)
and niacin (13% RDA), but also vitamin C (12% RDA) and,
surprisingly, vitamin B6(33% RDA). Ascorbic acid is added to
prune juice during processing, so different brands may contain
varying amounts of vitamin C. One brand was reported to have
as much as 61.4 mg ascorbic acid per cup, i.e., 68% RDA (Boato
et al., 2002). Prune juice contains less fat-soluble vitamins than
dried plums, because some pulp and skin are removed during
processing.
The only vitamin mentioned prominently on the label of
dried plums packaged in the United States. is vitamin A. Ac-
cording to new conversion factors recommended by the Food
and Nutrition Board (Institute of Medicine, 2001), the provita-
min A activity of carotenoids in plant food should be expressed
in retinol activity equivalents (1 μg Retinol Activity Equiva-
lent (RAE) =12 μgβ-carotene, or 24 μg other provitamin A
carotenoids). The USDA SR 25 database for carotenoids in dried
plums lists 394 μgβ-carotene, 57 μgα-carotene, and 93 μg
β-cryptoxanthin per 100 g (Table 1), which amounts to 39 μg
RAE/100g. Therefore, 100 g of dried plums may deliver only
4.3% of vitamin A RDA, and a cup of prune juice has negligi-
ble vitamin A activity. The food industry still uses International
Units (IU) of vitamin A activity (1 IU =0.6 μgβ-carotene,
or 1.2 μg other provitamin A carotenoids), which should be
applied only to pharmaceutics if at all. At the present time, the
rules of conversion and calculation of vitamin A activity for food
labeling purposes remain the same from 1993 (Federal Regis-
ter). Calculated in IU, 40 g serving of dried plums has 313 IU,
which is 6.3% of 5000 IU, the daily value (DV) for vitamin A
(per 2000 kcal).
Dried plums have a high content of vitamin K1 (phylloqui-
none), higher than any other fruit, fresh or dried, and comparable
to cashews and hazelnuts (Dismore et al., 2003). The range of
vitamin K1 in US dried plums is 51–68 μg/100 g, while in
fresh plums it is only 4.4–7.9 μg/100 g, which indicates that
the analyzed fresh plums were probably not of a prune-making
variety. High amounts of dietary vitamin K may interfere with
anticoagulation therapy prescribed for thromboembolic disease
patients, who must avoid certain foods, such as dark leafy greens
(containing 300–880 μg vitamin K1/100g).
Organic Acids
Quantification of organic acids in dried plums has been a
subject of controversy, since the older methods of analysis mea-
sured total acids and expressed them as equivalents of malic or
HEALTH EFFECTS OF DRIED PLUMS AND THEIR PRODUCTS 1281
citric acid. Very careful repeated extractions with ion exclusion
chromatography and electrochemical detection provided better
data on organic acids in various fruits (Kayano et al., 2003a).
Prune-making plums were found to contain 1.1 g of quinic
acid and 0.29 g of malic acid per 100 g, while dried plums
had 4.3 g and 1.1 g of these acids, respectively. Fresh Japanese
plums (Prunus salicina) contained only 0.32 g quinic acid/100g,
while it was not detectable in ume plums (Prunus mume). Prune
juice may have lemon juice, lime juice, or citric acid (2.4 g/L),
added as acidulants (Somogyi, 2005). The acids provide char-
acteristic taste and tartness of dried plum. Possible health ef-
fects of quinic acid metabolites are discussed in the following
sections.
Dried plums contain moderate amounts of oxalic acid (4.4 mg
per 47.5 g serving), while prune juice has 8.7 mg per cup, ac-
cording to NDS-R data (Table 1). It appears that the value for
prune juice was calculated from the German data for “100%
plum juice, P. domestica” (3.4 mg/100 mL). The same study
(Hon¨
ow and Hesse, 2002) reported an average of 1.7 mg ox-
alate/100 g of fresh plums. An older assessment of oxalate in
English diet found 3.4 mg/100 g in the stewed giant Victoria
prunes (Zarembski and Hodgkinson, 1962). A low-oxalate diet,
prescribed for people with calcium oxalate kidney stones, limits
the consumption of moderate-oxalate foods to three servings per
day, but high-oxalate foods (>7 mg/serving) should be avoided
entirely (University of Pittsburgh Medical Center (UPMC),
2006).
Volatile Compounds
The flavor of dried plums depends to some extent on the
volatile compounds, some of which are released in the mouth
during chewing and may reach olfactory mucosa. A study
of volatiles appearing during dehydration of prune-making
plums found only 1-hexanol, nonanal, and an unidentified ke-
tone in the headspace of whole fresh plums (Sabarez et al.,
2000). The homogenization of fresh plums caused release of
hexanal, 2-hexenal, and phenylacetylaldehyde. During simu-
lated commercial drying (18 hours, 80C, air velocity 5 m/s),
periodic sampling of headspace revealed disappearance of
the three C6compounds (hexanol, hexanal, and 2-hexenal)
and the generation of benzaldehyde, ethyl cinnamate, and 2-
furancarboxaldehyde after 7–9 hours. Benzaldehyde, with an
almond-like odor, is a product of amygdalin degradation, while
2-furancarboxaldehyde is probably derived from Maillard reac-
tions or caramelization of sugars.
The first step of the Maillard reactions involves formation
of Amadori compounds, nonvolatile precursors of color, aroma,
and flavor of processed foods. Dried plums were found to con-
tain 2-furoylmethyl derivatives of lysine, γ-aminobutyric acid,
alanine, and proline (20.6, 21.6. 4.5 and 3.6 mg/100 g, respec-
tively), which are common Amadori compounds (Sanz et al.,
2001).
Antioxidants
Antioxidant compounds in prune-making plums undergo
considerable degradation during processing due to high tem-
perature, cell disruption, and activation of oxidizing enzymes
(Stacewicz-Sapuntzakis et al., 2001). The antioxidants remain-
ing after processing are mainly phenolic compounds, but also
include fat-soluble carotenoids and α-tocopherol, as well as
water-soluble ascorbic acid.
Minor Antioxidants in Dried Plums
The best estimate of carotenoids in dried plums was the
unpublished study by F. Khachik (2000, personal communica-
tion), which was used for carotenoid values in the USDA SR
25 data and for the calculation of vitamin A activity. The av-
erages of 24 samples of dried plums, their standard deviation,
and ranges for 13 carotenoids and isomers are listed in Table 5.
All carotenoids measured in this study are absorbed in humans
and appear in plasma after ingestion. Some of these carotenoids
may be partially converted to vitamin A (all β-carotene isomers,
γ-carotene, α-carotene, and β-cryptoxanthin). The concentra-
tion ranges for individual carotenoids are quite wide, depending
on the original content in prune-making plums and degradation
during processing.
Tocopherols and ascorbic acid are also greatly degraded in
prunes and do not contribute much to total antioxidant activ-
ity. When two prune-making Croatian cultivars were processed
into dried plums (Druˇ
zi´
c et al., 2007), their vitamin C content
decreased from 8.6 and 9.8 mg/100 g to 2.5 and 2.6 mg/100 g
FW, respectively. These results are in good agreement with ear-
lier USDA estimates of vitamin C in dried plums (Stacewicz-
Sapuntzakis et al., 2001), but the USDA SR 25 value for vi-
tamin C in dried plums is only 0.6 mg/100 g (Table 1). The
amount of vitamin C in dried plums depends on the variety of
prune-making plums, drying parameters, and the duration of
storage (Piga et al., 2003; Del Caro et al., 2004). Higher drying
Tab le 5 Carotenoids in dried plums (mean of 24 samples)
Carotenoid μg/100g SD Range (min–max)
Lutein 107.743.758.0–223.1
Zeaxanthin 21.17.711.4–43.0
Anhydrolutein 5.31.73.1–10.8
α-Cryptoxanthin 5.82.22.8–11.4
β-Cryptoxanthin 44.520.914.5–91.6
Neurosporene 7.87.10.0–33.0
γ-Carotene 26.111.410.6–60.5
α-Carotene 22.113.210.4–68.5
trans-β-carotene 118.159.938.3–271.1
9-cis-β-carotene 34.417.813.1–83.5
13-cis-β-carotene 12.97.24.6–32.4
Phytofluene 10.05.72.0–25.0
Phytoene 16.07.54.4–34.8
Note: From Dr. Frederick Khachik, Department of Chemistry and Biochem-
istry, University of Maryland, College Park, MD (unpublished data, personal
communication, December 1, 2009).
1282 M. STACEWICZ-SAPUNTZAKIS
Tab le 6 Antioxidant capacity measurements for dried plums and prune juice
Total ORAC H-ORAC L-ORAC TEAC TRAP FRAP
(μmol TE/100 g) (μmol TE/100 g) (μmol TE/100 g) (μmol TE/100 g) (μmol TE/100 g) (μmol Fe/100 g)
Dried plums:
USDA, 2007 6552 6463 179
Wu et al., 2004 8578 8399 179
Prior et al., 2007 8244
Prior et al., 2007 2127
Pellegrini et al., 2006 1482 2300 6054
Prune juice:
USDA, 2007 2036 2036
Prior et al., 2007 2127
temperature (85C,followedby70
C) destroyed more ascorbic
acid than lower drying temperature (60C) in two varieties of
Italian prune-making plums, and a further 50% of vitamin C
was lost during 4–12 months of storage (at 20C, in polypropy-
lene bags, relative humidity 50% inside the package).
Antioxidant Capacity Measurements
Total antioxidant capacity of foods is measured by various
chemical assays, using different radical or oxidant sources. The
oxygen radical absorbance capacity (ORAC) assay uses 2,2-
azobis(2-amidinopropane) dihydrochloride (AAPH) as a per-
oxyl radical generator, a fluorescein probe, and a Trolox (a
water-soluble vitamin E analog) standard. Lipophilic (L-ORAC)
and hydrophilic (H-ORAC) antioxidant capacities are measured
separately on extracts of food, and the values added to provide
total ORAC in Trolox equivalents (TE) (Wu et al., 2004). A sim-
ilar assay using fluorescence of R-phycoerytrin is called total
radical-reducing antioxidant power (TRAP). The Trolox equiv-
alent antioxidant capacity (TEAC) is based on the ability of
antioxidants to quench the 2,2-azinobis(3-ethylbenzothiazoline-
6-sulfonic acid) (ABTS) radical, compared to the Trolox stan-
dard. The method based on the reduction of ferric complex with
2,4,6-tripyridil-s-triazine (TPTZ) to ferrous form is named as
the ferric reducing antioxidant power (FRAP) assay.
The values obtained by different assays on the same sam-
ples of dried plums (Pellegrini et al., 2006) are presented in
Table 6, as well as the results from different studies conducted
around the world. Table 7 shows that the antioxidant capacity
per unit of FW is higher in dried plums than in prune-making
plums, but not directly proportional to total phenolics content
(Druˇ
zi´
c et al., 2007; Walkowiak-Tomczak, 2008b). Air drying
preserved the antioxidant capacity of plums based on dry weight,
and even increased it in plums dried at 60C, while osmotic de-
hydration with subsequent air drying reduced it by 37–45%
(Table 7, Walkowiak-Tomczak, 2008b). In an Italian study of
two prune-making plum varieties, antioxidant capacity per unit
of dry weight was measured using the radical 2,2-diphenyl-1-
picrylhydrazyl (DPPH), and it increased significantly in both
varieties of plums dried first at 85C and then at 70C (total
time 38–44 hours; Piga et al., 2003). Continuous drying at 60C
(60–72 hours) increased antioxidant capacity in cv Sugar, but
slightly decreased it in cv President.
The results of various chemical assays, based on different
principles, cannot be compared directly and their biological
relevance is debatable. The problem is whether the antioxidants
in food can be absorbed and alter antioxidant status in vivo.
Changes in plasma ORAC after consumption of dried plums
or prune juice were measured in six healthy older women, who
were given 315 mL prune juice, or 131 g of dried plums blended
in 315 mL water, or 315 mL water (control) in a randomized
Tab le 7 Effect of processing on total phenolics and antioxidant capacity
Total phenolics Total phenolics TEAC TEAC
DW(%) (mgCAE/100gDW) (mgCAE/100gFW) (μmol TE/100 g DW) (μmol TE/100 g FW)
Fresh plums 15.9 1836 292 12220 1943
Dried plums:
Air (60C) 76.1 2140 1629 15,160 11,537
Air (40, 60, 80C) 75.2 2448 3255 12,290 9242
Osmotic dehydration (24 hr, 60C) 88.8 1347 1196 7730 6864
Osmotic dehydration (72 hr, 60C) 88.4 1036 916 6670 5896
Adapted from Walkowiak-Tomczak (2008b)
Fresh plums, var. Elena 174
Fresh plums, var. Bistrica 231
Dried plums, var. Elena 529
Dried plums, var. Bistrica 562
Adapted from Druˇ
zi´
c et al. (2007)
HEALTH EFFECTS OF DRIED PLUMS AND THEIR PRODUCTS 1283
Tab le 8 Total phenolics in dried plums and prune juice
Catechin
Range equivalents
(mg GAE/100 g) (mg GAE/100 g) (mg/100 g)
Dried plums:
USDA, 2007 745 165–1392
Wu et al., 2004 1195
Druˇ
zi´
c et al., 2007 529,562
Prior et al., 2007 1400
Vinson et al., 2005 788
Karakaya et al., 2001 368
Prune juice:
Boato et al., 2002 180.5
Lugosi and Hovari, 2003 180.1
Prior et al., 2007 350
crossover design (Prior et al., 2007). Although these doses of
prune juice or dried plums had total ORAC values of 10.8 and
6.7 mmol TE, respectively, the plasma H-ORAC and L-ORAC of
treated subjects did not differ significantly from controls during
five hours post-dosing. However, in a study of 27 women (25–54
year old) consuming twice a day a snack of dried plums (100
kcal each) for two weeks, serum antioxidant capacity, measured
by the TEAC assay, was significantly increased (Kaper et al.,
2010). Equicaloric snacks of low-fat cookies had the opposite
effect in these women.
Phenolic Compounds
Phenolic compounds are the main source of antioxidants
in dried plums. Total phenolics (TP) for dried plums and prune
juice measured in gallic acid equivalents (GAE; Wu et al., 2004)
are reported in USDA tables of ORAC (USDA 2007b). The TP
assay is based on the Folin–Ciocalteu colorimetric assay and
calibrated against gallic acid, chlorogenic acid, or catechin so-
lutions. Table 8 presents the results of TP determinations from
various studies of dried plums and prune juice. Compared with
other dried fruits, only dried cranberries and dates have higher
values of total phenolics based on catechin equivalents (CE)
(Vinson et al., 2005), but dried plums have the highest value
among dried fruits when TP content is based on gallic acid
equivalents (Wu et al., 2004; Pellegrini et al., 2006). However,
the best standard for measuring total phenolics in dried plums
and their products is probably chlorogenic acid, because the iso-
mers of this compound are the main phenolics in prune-making
plums and they are not greatly degraded during processing. The
total phenolics in plums are nearly doubled when expressed
on chlorogenic acid equivalents (CAE) instead of gallic acid
equivalents (Chun and Kim, 2004). In a study of the effect of
fresh plum processing on TP content of resulting dried plums
(Walkowiak-Tomczak, 2008b), the value of total phenolics ex-
pressed in CAE/100 g dry weight increased in air-dried plums,
but decreased in plums that were osmotically dehydrated in 70%
sucrose and then air-dried at 60C (Table 7). Calculated per unit
of FW, total phenolics are always higher in dried plums than in
precursor prune-making plums, due to the concentration effect
(Druˇ
zi´
c et al., 2007; Walkowiak-Tomczak, 2008b), despite the
degradation of phenolic compounds during heat processing.
Spiking of human plasma with food extracts, beverages, or
antioxidant compounds may also provide an estimate of antiox-
idant activity, although it bypasses absorption and metabolism
in the body. Prune juice was tested in vitro for the ability to
inhibit human lipoprotein (LDL +VLDL) oxidation by 50%
(IC50) and increase lag time by 50% (CLT50) (Vinson et al.,
1999). Both parameters, expressed as μM concentrations of
total phenolics, were similar for prune juice, coffee, and chloro-
genic acid. Another study (Kasai et al., 2000) showed an in-
hibitory effect of various high-performance liquid chromatog-
raphy (HPLC) fractions of “prune” extract on lipid peroxide-
induced 8-hydroxydeoxyguanosine (8-OHdG) formation from
deoxyguanosine in vitro. However, the extract was prepared
from fresh plums of unspecified variety (personal communi-
cation from Dr. H. Kasai, October 6, 2010). The inhibitory
fractions were determined to be isomers of chlorogenic acid.
The authors also investigated the effect of chlorogenic acid on
DNA oxidation in rat tongue. The animals treated with oxy-
gen radical forming carcinogen, 4-nitroquinoline-1-oxide in the
drinking water and fed with a diet containing chlorogenic acid
(250 mg/kg) did not have an elevated level of 8-OHdG in DNA
from tongue mucosa, compared with the treated rats fed with
basal diet. Chlorogenic acid did not alter normal 8-OHdG for-
mation in animals that were not treated with the carcinogen.
Isomers of chlorogenic acid (5-O-caffeoylquinic acid) are
the principal phenolic compounds in dried plums, and also
include neochlorogenic (3-O-caffeoylquinic acid) and cryp-
tochlorogenic acid (4-O-caffeoylquinic acid) (Nakatani et al.,
2000; Prior et al., 2007). Table 9 shows the proportion of these
isomers in dried plums—the most abundant is neochlorogenic
acid, cryptochlorogenic acid is fairly high, and chlorogenic acid
is a minor component. In some studies cryptochlorogenic acid
and chlorogenic acid were not separated by HPLC and reported
together as chlorogenic acid (Piga et al., 2003). Many stud-
ies do not separate isomers and report only total chlorogenic
acid (Amakura et al., 2000, for prune juice). Long drying of
plums at low temperature (60–72 hours, 60C,) partially de-
graded chlorogenic acids, while shorter drying at high tem-
perature (38–44 hours, 85C) preserved them in dried plums.
Anthocyanins, mostly cyanidin-3 rutinoside, were totally de-
stroyed by drying, and so were catechins (Piga et al., 2003).
Small amounts of flavonoid rutin (quercetin-3-rutinoside) may
persist in some varieties, which were exceptionally rich in this
compound (cv President). The USDA database (USDA, 2007a)
for the flavonoid content of selected foods lists quantities of
flavonoids occasionally found in dried plums (Table 9).
The content of chlorogenic acids (94% of all extracted phe-
nolic compounds) in dried plums accounts for only 30%
of their exceptionally high total antioxidant capacity, which
suggests the presence of large amounts of other antioxidant
molecules (Kayano et al., 2003b). Liquid chromatography–mass
1284 M. STACEWICZ-SAPUNTZAKIS
Tab le 9 Individual phenolic compounds in dried plums and prune juice (mg/100 g)
Dried plums,
USDA (2007b)Prune juice, Amakura
et al. (2000)
Prune juice, Prior
et al. (2007)
Dried plums
Nakatani et al. (2000)
Dried plums, Kayano
et al. (2003b)
Dried plums, Prior
et al. (2007) Mean Range
Chlorogenic acids (total) 19 101.6 107.7 152.5
Neochlorogenic
(3-CQA)
55.5 133 91.6
Cryptochlorogenic
(4-CQA)
38.131 51.1
Chlorogenic acid
(5-CQA)
86.79.9
Gallic acid 2.1
Caffeic acid 2.6
Proanthocyanidins 62
Cyanidin 0.71 0.0–2.4
Delphidinin 0.04 0.0–0.2
Quercetin 1.80.0–4.0
spectrometry (LC–MS) of dried plum extracts revealed the pres-
ence of 40 minor components (Table 10), mostly simple phenolic
acids (caffeic, ferulic, gallic, protocatechuic, p-hydroxybenzoic,
and p-coumaric), their glycosides and esters (Fang et al., 2002).
However, they were not quantified and taken together would
hardly explain the high ORAC value of dried plums. Japanese
researchers extracted and characterized a plethora of minor
novel compounds from California dried plums (Table 10), some
of which had high ORAC value or acted synergistically with
chlorogenic acids in vitro, raising their antioxidant capacity
(Kayano et al., 2002, 2004a, 2004b; Kikuzaki et al., 2004).
Again, the absence of quantification prevents concluding that
some of them may be responsible for high antioxidant activity
of dried plums.
Fresh plums (unspecified varieties) contain small amounts of
catechin and epicatechin, but careful analytical techniques in-
dicate high quantities of proanthocyanidins that are polymeric
forms of flavan-3-ols. These are very difficult to extract from
the plant matrix and do not fully elute from HPLC columns, or
elute as a broad peak (Prior and Gu, 2005). The USDA database
(USDA, 2004) lists the proanthocyanidin content for plums (un-
specified varieties) with large proportion of high polymers (>10
units of catechin and epicatechin), but it does not contain values
for dried plums. The USDA data are based on the survey per-
formed by Gu et al. (2004), who did not find proanthocyanidins
in dried prunes (unpublished observation). Fresh prune-making
plums (cv d’Agen) were found to contain proanthocyanidins in
the pulp (0.79 mg/g DW) and skin (0.59 mg/g DW) (Raynal
et al., 1989). The authors suspected that these values may be un-
derestimated due to the difficulty of assaying highly condensed
polyphenols, which may be insoluble or bound to cell walls.
Small amounts of proanthocyanidin dimers were also found
in prune-making varieties of Polish plums (W
egierka Zwykła,
W
egierka Łowicka, and W
egierka D
abrowicka), but the sam-
ple preparation probably removed higher polymerization forms
(Ło´
s et al., 2000). Japanese researchers found that large amounts
of insoluble phenolic compounds are present in the residue re-
maining after ethanolic extraction of California dried plums
Tab le 1 0 Other phenolic compounds in dried plums
Fang et al. (2002) Feruloquinic acids
Coumarylquinic acids
Trihydrocinnamoylquinic acids
Dicaffeoylquinic acids
Caffeoylshikimic acids
Gallic acid and its hexoside
Protocatechuic acid and its hexoside
p-hydroxybenzoic acid and its hexoside
Vanilic acid and its hexoside
Methoxybenzoic acid and its hexoside
Methoxybenzoic acid rhamnoside
Caffeic acid and its hexoside
Syringic acid and its hexoside
Methoxycinnamic acid hexoside
p-coumaric acid and its hexoside
Ferulic acid and its hexoside
Kayano et al.
(2002)
p-coumaric acid
Protocatechuic acid
Vanilic acid glucoside
4-amino-4-carboxychroman-2-one
Kayano et al.
(2003b)
(-)-epicatechin
7-methoxycoumarin
Kayano (2004a,
2004b)
Coniferin
Scopoletin
Magnolioside
Rutin
Ferulic acid glucopyranoside
Vanilic acid glucopyranoside
(+)-Pinoresinol glucopyranoside
9-glucopyranosyl-7-(4-hydroxy-3-methoxyphenyl-1-
(3-hydroxy-propyl)-
3-methoxy-dihydro-benzofuran
Benzyl b-primeveroside
2-(5-hydroxymethyl-2,5-dioxo-2,3,4,5-tetrahydro-1H-
1,3-bipyrrole)carbaldehyde
Kikuzaki et al.
(2004)
Abscisic acid
Abscisic acid glucopyranoside
Roseoside
Dihydroxy-dimethyl-7-oxa-6-oxobicyclo-oct-8-yl-3-
methyl-pentadienoic acid
Dihydroxy-dimethyl-7-oxa-6-oxobicyclo-oct-8-yl-3-
methyl-pentadienoic acid glucopyranoside
Trihydroxy-dimethyl-7-oxa-6-oxobicyclo-oct-8-yl-3-
methyl-pentadienoic acid
HEALTH EFFECTS OF DRIED PLUMS AND THEIR PRODUCTS 1285
(Kayano et al., 2003b). These could be extracted after acid hy-
drolysis of the residue and the obtained fraction had high total
phenolics and ORAC value. Colorimetric test for proanthocyani-
dins yielded 62 mg/100 g of dried plums. Subsequent research
revealed the presence of oligomers (average polymerization =
5) composed of catechin and epicatechin units, with the an-
tioxidant potency higher than that of chlorogenic acid (Kimura
et al., 2008).
Proanthocyanidins of dried plums should be further analyzed
by phloroglucinolysis (Hagl et al., 2011), or thiolytic depoly-
merization (Nunes et al., 2008) that yield more accurate quantifi-
cation. Such analysis of French and Portuguese fresh plums (not
prune-making varieties) doubled the total amount of phenolics
recovered from crude extract and revealed very high proportion
of proanthocyanidins (45–92% of total phenolics, depending on
plum variety).
Metabolites of Dried Plum Phenolics
The major phenolic compounds in dried plums, isomers of
chlorogenic acid, are partially absorbed in the small intestine of
humans, as inferred from studies with ileostomy subjects (Olthof
et al., 2001). Seven healthy subjects without a colon ingested 1 g
of chlorogenic acid or 0.5 g of caffeic acid. On the average, 67%
of chlorogenic acid was recovered within 24 hours in ileostomy
effluent, but only 5% of caffeic acid. Little chlorogenic acid was
recovered from urine (0.3%), but 11% of caffeic acid dose was
excreted. Caffeic acid was also excreted in urine after ingestion
of chlorogenic acid (0.2% of the dose). It seems that 33% of
the chlorogenic acid dose was absorbed unchanged in the upper
gastrointestinal track, and extensively metabolized in the liver
or kidney. Chlorogenic acid was not hydrolyzed in the stom-
ach or the intestinal lumen of these patients. In subjects with
healthy colons, chlorogenic acid is hydrolyzed into caffeic acid
and quinic acid by the colonic microflora (Olthof et al., 2003).
Human fecal bacteria were shown to metabolize both chloro-
genic acid and caffeic acid in vitro (Gonthier et al., 2006). The
major final product of bacterial and endogenous metabolism
of caffeic and quinic acids is benzoic acid, subsequently
conjugated with glycine by the liver or kidney, and excreted
in urine as hippuric acid (Olthof et al., 2003).
There are many other minor metabolites appearing in plasma
and urine in trace amounts, which could transiently exert an-
tioxidant effects after ingestion of chlorogenic acid-rich foods
(coffee, dried plums). Most of them are hydroxycinnamic acids
(caffeic, ferulic) and their derivatives, of which the caffeic acid
has the highest antioxidant activity (Shahidi and Chandrasekara,
2010). Very few studies describe the metabolism of dried plum
phenolics in humans. Plasma and urine samples were collected
from three healthy volunteers after ingestion of a single dose of
100 g California dried plums to check for the presence of hy-
droxycinnamates (Cremin et al., 2001). Chlorogenic acid was
below the level of detection in plasma, but small amounts were
recovered from urine, especially at two and four hours after
dosing (19–35 nM concentration). Caffeic acid, in a free and
conjugated forms (sulfate and glucuronate), was more abun-
dant in urine (265–475 nM) and increased 1.5–3 fold after dried
plum consumption. This study compared plasma levels of ferulic
and caffeic acid before and two hours after ingestion of dried
plums and found an increase of caffeic acid in two out of three
subjects (40 nM). Another study of 10 healthy volunteers fol-
lowed plasma and urine levels of phenolic compounds for eight
hours after ingestion of encapsulated green coffee extract as
a single dose containing 170 mg (451 μM) chlorogenic acids
(Farah et al., 2008). There was a great variability in the apparent
bioavailability of chlorogenic acids among the subjects, from 8
to 72% of the dose, with a mean of 33%. The apparent bioavail-
ability was calculated from area under the curve of plasma phar-
macokinetic profiles, which were very different for individual
subjects, with single or multiple peaks in plasma concentra-
tion. Maximal plasma concentration (Cmax) of total chlorogenic
acids was 14.8 ±11.7 μM(6μg/mL), while the average time
to reach it, Tmax, was 3.1 ±2.6 hours. Caffeic and ferulic acids
were relatively minor phenolic compounds in plasma of these
subjects, while caffeoylquinic and dicaffeoylquinic acids were
predominant. A similar study of 11 healthy volunteers drink-
ing one dose of instant coffee beverage containing 412 μM
chlorogenic acids yielded very different results (Stalmach et al.,
2009). The samples of plasma and urine were collected for
24 hours and the total recovery of metabolites in urine was
similar in both studies (29% of the dose). Plasma Cmax of to-
tal metabolites was only 1.15 ±0.26 μM(<0.5 μg/mL) and
there was much less individual variability among subjects. The
differences between the results of these two similar studies of
coffee phenolics metabolism may stem from the preparation
of plasma and urine samples before chromatographic analysis
(HPLC–photodiode array (PDA)–MS). The Farah et al. (2008)
study treated the samples with β-glucuronidase and sulfatase,
while the Stalmach et al. (2009) study did not. Although the
second study found the metabolite forms of coffee chlorogenic
acids in circulation, it may have had problems with recovery of
all metabolites present in plasma. The major metabolites iden-
tified in plasma were dihydroferulic acid and its sulfate, ferulic
acid sulfate, caffeic acid sulfate, and dihydrocaffeic acid sul-
fate (Stalmach et al., 2009). The major phenolic compounds
excreted after green coffee extract consumption were sinapic,
gallic, p-hydroxybenzoic, and dihydrocaffeic acid (Farah et al.,
2008), while the other study identified dihydrocaffeic acid sul-
fate, feruloylglycine, dihydroferulic acid sulfate, and ferulic
acid sulfate as the main urinary metabolites (Stalmach et al.,
2009).
As early as 1914, it was noticed that consumption of dried
plums (300 g) greatly increased the excretion of hippuric acid in
the urine (Blatherwick, 1914; Blatherwick and Long, 1923) of
two healthy subjects. Eating as little as 1.5 g of dried plums per
kilogram body weight (BW) per day caused a striking elevation
of hippuric acid in serum and urine in five healthy subjects
(Cathcart-Rake et al., 1975). This effect was confirmed by a
1286 M. STACEWICZ-SAPUNTZAKIS
Tab le 1 1 Composition of plum/prune products (per 100 g FW)
Component Plum juice concentrate Prune puree Prune juice concentrate Dried plum powder
Water (g) 29.6 30.0 30.5 3.5
Energy (kcal) 268 257 254 330
Protein (g) 2.28 2.10 2.34 3.00
Fat (g) 0.1 0.2 0.11 0.5
Total carbohydrate (g) 65.5 65.1 64.5 86.2
Total dietary fiber (g) 1.9 3.3 4.0 9.9
Soluble fiber (g) 1.7 3.7 5.0
Insoluble fiber (g) 0.2 0.3 4.9
Total sugars (g) 39 45
Glucose (g) 23.3 22.3 30.6 15.2
Fructose (g) 11.8 13.9 14.5 28.7
Sucrose (g) 3.7 0.68 1.1
Sorbitol (g) 17.0 14.1 17.8 25.1
Minerals
Ca (mg) 45.3 31.3 41 72
Fe (mg) 1.03 2.80 1.52 3.00
K (mg) 834 852 752 1050
Na (mg) 65.3 23.0 52.2 5.0
Mg (mg) 51.5 45.8
P (mg) 75.9 71.7 72.9 108
Zn (mg) 0.57 0.43
B (mg) 1.98 2.60 3.4
Quinic acid (g) 3.38 3.22
Malic acid (g) 0.86 0.85
Vitamins
Vitamin A (IU) 25.5 2000 119 1760
Vitamin C (mg) Trace 4.3 2.83 0.63
Vitamin E (IU) Trace 0.73
Thiamin (mg) 0.04
Niacin (mg) 2.5
Panthotenic acid (mg) 0.43
ORAC (μM TE) 13,040 19,840
Total phenolics (mg GAE) 987 686
Tannins (mg catechin equivalents) 19
Gallic acid (mg) 312
Chlorogenic acid (mg) 46.5 4
Neochlorogenic acid (mg) 198.5 8.3
Cryptochlorogenic acid (mg) 10.8
Rutin (mg) 0.07
Note: The data are product specifications obtained from Sunsweet Growers Inc. (personal communication, June 15, 2010) except values marked in italics (prune
puree: estimated glucose, fructose and vitamin A from USDA, 2012; dried plum powder: P and B from Hooshmand and Arjmandi, 2009; ORAC and total phenolics
from Shukitt-Hale et al., 2009; chlorogenic acids from Yang and Gallaher, 2005).
ORAC values were converted to μM/100 g.
study of six subjects consuming prune juice (315 mL) or dried
plums (131 g), whose urine was collected for six hours (Prior
et al., 2002). Chlorogenic acid was not found in the urine of these
six subjects, even after enzymatic hydrolysis with sulfatase and
glucuronidase. Another major fraction of phenolics in dried
plums, proanthocyanidins, cannot be absorbed in the intestine,
but may be depolymerized in the colon by local bacteria and
slowly converted to catechin and epicatechin monomers (Rios
et al., 2003). The flavan-3-ol monomers are further metabolized
to valerolactones, which may be absorbed and excreted in urine,
or converted to benzoic, and finally hippuric acid (Olthof et al.,
2003). Therefore, the increase in urinary excretion of hippuric
acid within 48 hours after ingestion of dried plums or prune
juice could reflect the metabolism and absorption of quinic acid
and phenolic compounds in the alimentary tract.
Composition of other Commercial Products
of Prune-Making Plums
Prune-making plums are processed into a variety of commer-
cial products, which serve as ingredients in the production of
other foods. Table 11 lists the components of fresh plum concen-
trate, prune juice concentrate, dried plum puree (prune puree),
and dried plum powder according to industrial specifications ex-
cept as noted. The various methods of processing prune-making
plums result in specific differences in composition, although
both concentrates and prune puree have similar water content
(30%). Plum juice concentrate is made of fresh plum juice from
mature plums cv d’Agen, and its composition is closest to fresh
plums. It contains sucrose (3.7 g/100 g FW) and significant
amounts of phenolic compounds, including gallic acid (rather
HEALTH EFFECTS OF DRIED PLUMS AND THEIR PRODUCTS 1287
Tab le 1 2 Carbohydrates in plum/prune products (g/100 g FW)
Plum juice concentrate Prune puree Prune juice concentrate Dried plum powdera
Water 37.025.738.314.5
Total dietary fiber 1.05.24.210.8
Oligosaccharides 8.60.80.64.3
Glucose 20.216.721.222.8
Fructose 11.515.713.412.0
Sucrose 7.50.20.22.4
Sorbitol 10.712.610.211.5
Inositol 1.82.51.92.2
Note: aDried plum powder, high moisture, 3% calcium stearate. Adapted from Bauer and Fahey (2004).
high amount, 312 mg/100 g FW). Prune juice concentrate is an
extract of dried plums made by cooking dried plums to release
soluble solids. The pulp is then removed from the extract and
the juice is concentrated in high vacuum evaporator. The con-
centrate is used for production of prune juice. It contains very
little sucrose (similar to dried plums) and insoluble fiber, which
is removed with pulp. Dried plum puree is a blend of prune juice
concentrate with dried plum paste, designed for use in baking to
replace 50% of fat. The paste is made by cooking dried plums
to 22–25% moisture, and blended with prune juice concentrate
(25–30% paste, 70–75% juice concentrate).
Dried plum powder has been used in many laboratory an-
imal experiments, as well as cell culture studies described in
next sections. It is a commercial industrial food ingredient com-
posed of 99% dried plums and 1% calcium stearate to prevent
caking. Low-moisture powder contains up to 3.5% water, but
one study reported as much as 14.5% moisture and 3% cal-
cium stearate (Dikeman et al., 2004). Some composition data
for dried plum powder in Table 11 are quoted from pertinent
animal studies (Yang and Gallaher, 2005; Hooshmand and Arj-
mandi, 2009; Shukitt-Hale et al., 2009). Dried plum powder is
86% carbohydrates, including 10% of total dietary fiber. The
industry-reported sugar composition, 28.7 g fructose and 15.2
g glucose/100g, is at odds with dried plums, which contain
more glucose than fructose. There seems to be a relatively
high amount of sorbitol, 25.1 g/100 g. However, a study of
carbohydrate composition found 22.8 g glucose and 12 g of
fructose/100 g of dried plum powder (Table 12), similar in
proportion to dried plums (Bauer and Fahey, 2004; Dikeman
et al., 2004). It also found 4.1% acid-hydrolyzed fat, no doubt
due to the presence of calcium stearate, and 13.7% sugar alco-
hols (sorbitol and inositol). Calcium content of 72 mg/100 g
in dried plum powder (Table 11) seems too low. Calcium
stearate (at 1%) provides additional 66 mg of calcium in dried
plum powder, or 198 mg calcium (as 3% calcium stearate)
per 100 g.
The content of chlorogenic acids measured by HPLC is about
seven-fold lower than in dried plums (based on dry weight),
probably because production of dried plum powder involves fur-
ther drying of prunes at high temperatures, which may degrade
phenolic compounds (Gallaher and Gallaher, 2009). However,
total phenolics measured by the Folin assay are in the range
reported for dried plums.
HEALTH EFFECTS ASSOCIATED WITH MAJOR
DRIED PLUM CONSTITUENTS
Gastrointestinal Health Effects
Dried plums have a long history of claims for preventing
constipation as described in the previous review (Stacewicz-
Sapuntzakis et al., 2001). In 1878, a preparation of “medicated
prunes” was advertised to relieve constipation and “bilious dis-
orders” (bloating, flatulence, heartburn, and dyspepsia; Kravetz,
2002). A similar preparation of prune concentrate and cascarin
(Prucara) was described as very effective in constipated patients
from several nursing homes (Stern, 1966). A laxative jam made
of dates and dried plums was used to increase the frequency
of bowel movements and decrease laxative medications in a
group of hospitalized veterans (64–94 year old) in Canada (Du-
rand et al., 1991). A geriatric hospital in Sweden introduced a
mixture of buttermilk, bran, and dried plums for breakfast with
excellent results (Lundberg, 1984). Prune whip yoghurt (yo-
ghurt with pureed dried plums) was very effective in regulating
bowel habits in a large group of elderly patients in a New York
hospital (Ferrer and Boyd, 1955). A study of mildly constipated
subjects in Finland compared control yoghurt (one cup/day)
with test yoghurt containing galacto-oligosaccharides, linseed,
and 12 g of dried plums in a crossover intervention (Sairanen
et al., 2007). The subjects reported that the test yoghurt was
more effective, but control yoghurt also increased defecation
frequency from the baseline. The above-quoted studies used
multiple agents to relieve constipation, so it is difficult to judge
the effect of dried plums alone. However, in a systematic Ger-
man population study, dried plums were perceived as the best
food to soften stool by people suffering from constipation, ir-
ritable bowel syndrome with constipation, or healthy controls
(M¨
uller-Lissner et al., 2005). They were asked which foods or
beverages altered stool consistency (open-ended question), and
then were specifically questioned about prunes, bananas, coffee,
tea, chocolate, beer, wine, and cigarettes.
The effect of dried plums or prune juice on intestinal motility
depends on health and sensitivity of the subjects. In a study of
38 postmenopausal women, recruited for evaluating the effects
of dried plum on bone biomarkers, who consumed 100 g dried
plums or 75 g dried apples daily for three months, there were
no differences in the self-reported bowel function between the
1288 M. STACEWICZ-SAPUNTZAKIS
treatments (the amount of fiber was nearly equal) and no change
from baseline before the treatments (Lucas et al., 2004). Snack-
ing on dried plums (100 kcal) compared with low-fat cookies,
twice a day for two weeks in a crossover design, promoted sig-
nificantly softer stools in 29 younger women (25–54 year old)
(Howarth et al., 2010). A study in Finland used specially pre-
pared prune juice, made from plum concentrate, prune puree,
water, and fructose to evaluate the effects on bowel function and
gastrointestinal complaints (Piirainen et al., 2007). The 54 vol-
unteers were followed for a week before treatment, two weeks
of ingesting 125 mL prune juice twice a day, and one week
after. There were fewer days with difficulty of defecation dur-
ing the treatment than before, and the effect continued into the
following week. However, more flatulence was reported during
treatment.
Plum juice (PlumSmart), made from fresh prune-making
plums with addition of prebiotic fiber (resistant dextrin), grape,
carrot, and blueberry juices, was tested on 36 adult US vol-
unteers with symptoms of constipation (Cheskin et al., 2009).
The study lasted six weeks and involved drinking 6 oz of plum
juice each day for two weeks, or 9 oz of apple juice with 3 g of
psyllium fiber, or apple juice alone, in randomized order. The
plum juice treatment resulted in softer stool than apple juice
alone or with psyllium, and the relief of multiple constipation
symptoms was as fast as with psyllium (within 24 hours). A
similar study was conducted with dried plums (100 g/day) ver-
sus psyllium (12 g/day) in an eight-week randomized crossover
trial (Attaluri et al., 2011). The subjects (n =40) had symp-
toms of mild to moderate chronic functional constipation. Each
treatment was administered in two doses per day (50 g dried
plums or 11 g psyllium in a dose, each containing 3 g fiber), for
three weeks. The number of bowel movements per week was
significantly higher with dried plum treatment than with psyl-
lium ((6.8 ±0.5 vs 5.7 ±0.6, p =0.002), but both treatments
improved constipation symptoms without causing any adverse
effects.
The Chinese Institute of Nutrition and Food Safety (2005)
conducted trials with dried plum extract on 120 subjects with
mild constipation symptoms. The subjects were randomly di-
vided into two groups: the intervention group received 50 mL
of the extract per day for seven days, while the control group
did not get any kind of treatment. The treated group had sig-
nificantly increased defecation frequency, from 2.2 to 4.6 per
week and decreased the score of defecation difficulty. The trial
subjects did not exhibit any adverse reactions.
From the available evidence, it seems that dried plums and
prune juice are considered as mild laxatives, but there is little in-
formation about possible diarrheal effect with increasing dose.
There was a study comparing prune juice with sorbitol syrup
(70%), castor oil, and sauerkraut juice for the purpose of devel-
oping a model of diarrheal illness of short duration and mild side
effects (Reele and Chodos, 1985). When the volunteers (n =5
or 6) ingested 4, 8, or 12 oz of prune juice, each dose caused
only a single loose stool in one or two subjects, and no side
effects were noted. A dose of sorbitol (30 mL, containing 21 g
sorbitol) caused transient (two hours) diarrhea in all five sub-
jects, and 60 mL (42 g sorbitol) resulted in a more severe, longer
lasting diarrhea, accompanied by abdominal cramps. Two doses
of sorbitol, each 45 mL (31.5 g), eight or six hours apart, pro-
duced similar response lasting 10 hours. Gastrointestinal effects
of sorbitol are described in two reviews of tolerance of low-
digestible carbohydrates (Livesey, 2001; Grabitske and Slavin,
2009). While small amounts of sorbitol have a humectant, stool-
softening effect, large doses rapidly change fluid balance in the
colon due to an osmotic effect. When the liquid stool is pushed
behind hard stool by high-amplitude propagating contractions,
the liquid portion exerts pressure on the bowel wall, like an in-
flating balloon, and may cause a severe cramping pain (McRorie
et al., 2000). Solid sources are slower to cause diarrhea than liq-
uids, divided doses are better tolerated, and an adaptation to
slowly increasing doses may occur.
Sorbitol is generally recognized as safe (GRAS) by Food
and Drug Administration (FDA), but processed food containing
sorbitol requires a label warning about possible laxative effects
if the consumption of sorbitol in this food is expected to exceed
50 g per day. European Codex Alimentarius requires such label
for the dose of 20 g sugar alcohols per day. Such amount of
sorbitol may be ingested in 167 g of dried plums (20 prunes)
or 328 mL (1.25 cup) of prune juice.
Intestinal motility may be aided by chlorogenic acids present
in dried plums and prune juice. Increased peristaltic activity was
observed in rats and mice after the application of chlorogenic
acid (Chok and Lang, 1961), and similar effect is found in many
human subjects after drinking coffee, which also contains this
compound. Minor phenolic compounds of dried plums, caffeic,
and ferulic acids were also shown to produce increased motility
of gastrointestinal tract. Ferulic acid produced concentration-
dependent contractions of isolated rat stomach fundus and
guinea pig ileum, as well as increased gastric emptying rate
and decreased intestinal transit time in the intact rats (Badary
et al., 2006).
Dried plums may contain another substance that causes se-
cretion of water and electrolytes into intestinal lumen, and also
induces intestinal contractions. It is serotonin, a neurotransmit-
ter and a regulator of gastrointestinal physiology. Fresh plums
(unknown varieties) contain considerable amount of serotonin
(3.6–5.7 μg/g; Feldman and Lee, 1985), and it would be advis-
able to check whether serotonin is also a constituent of dried
plums. Exogenous serotonin was extensively studied in exper-
imental animals (Salvador et al., 2000), and was found to in-
crease intestinal fluid secretion and gut motility; however, it is
unknown if the amount of serotonin in dried plum, if present,
would cause similar effects.
Dried plums may also have a prebiotic effect, promot-
ing growth of beneficial bacteria (saccharolytic anaerobes and
aciduric organisms) in the colon. In vitro, sorbitol is fermented
by colonic bacteria to short-chain organic acids, especially bu-
tyric acid, which in vivo maintains healthy colonic epithelium
by contributing to an anti-inflammatory and anti-neoplastic
environment (Livesey, 2003). Dried plums contain very little
HEALTH EFFECTS OF DRIED PLUMS AND THEIR PRODUCTS 1289
oligosaccharides (Dikeman et al., 2004), but their high fiber and
sorbitol content may provide additional fermentation substrate
for healthful colonic bacteria. In rat, dietary sorbitol has a spar-
ing effect on thiamine and other B vitamins (Morgan and Yud-
kin, 1957) due to a remarkable promotion of colonic bacterial
synthesis. However, in an experiment with human subjects fed
with sorbitol (70 g/day, 6–10 days) along with a low-thiamine
diet, no significant increase of urinary excretion of thiamine was
noticed, and the authors concluded that sorbitol did not increase
colonic production of this vitamin (Peppler et al., 1960). Inter-
estingly, not all of the 10 subjects in this experiment developed
diarrhea despite the large dose of sorbitol.
Bone Preservation
Dried plums contain many compounds which could con-
tribute to bone health and probably act synergistically. Among
them, copper, boron, and vitamin K1 are particularly abundant
and a regular intake of dried plums would help to satisfy the
dietary requirements (Table 3). Vitamin K promotes bone min-
eralization, since it is a cofactor in γ-carboxylation of osteo-
calcin, which regulates the growth of hydroxyapatite crystals in
the bone (Zittermann, 2001). Boron reduces urinary excretion
of calcium and magnesium and elevates estradiol levels in post-
menopausal women (Devirian and Volpe, 2003). Other minerals
in dried plums, especially potassium, may also help to maintain
bone mineral density (BMD).
Cell Culture Studies
Various polyphenols were also found to influence bone
turnover. An extract was prepared from dried plum powder and
used in a series of in vitro cell culture experiments. Mouse
macrophage cells (RAW264.7) were used as osteoclast pre-
cursors to study the effect of dried plum phenolics on their
differentiation and activity (Bu et al., 2008). The osteoclast dif-
ferentiation was inhibited under normal, oxidative stress, and
inflammatory conditions by incubation with the extracts, and
the results were confirmed in mouse bone marrow cultures and
resorption pit formation assay on dentin slices. Another type of
cell, MC3T3-E1, mouse preosteoblastic cells, was used to eval-
uate the dried plum powder extract effect on osteoblast activity
and mineralization (Kamkar et al., 2005; Kamkar et al. 2006;
Hooshmand et al., 2008; Bu et al., 2009). Calcified nodule for-
mation was dose-dependently increased with concentration of
dried plum phenolics (0.5–1000 μg/mL; Kamkar et al., 2005; Bu
et al., 2008). Alkaline phosphatase activity in cell medium was
significantly increased by 100 μg/mL extract (Kamkar et al.,
2006), and a similar effect was observed in the cells even at
lower concentrations (2.5–20 μg/mL; Bu et al., 2009). IGF-I
production was upregulated by a high dose of 1000 μg/mL in
one laboratory experiment (Hooshmand et al., 2008) and by
only 5 μg/mL in another (Bu et al., 2009). However, variability
of response was so large that 10-μg/mL dose was not signif-
icantly different from control. Lysyl oxidase, an enzyme in-
volved in bone matrix synthesis, was also upregulated by 5- and
10-μg/mL extracts, while the receptor activator of the NFκ-B
ligand (RANKL) expression was downregulated under inflam-
matory conditions.
Judging from their effects on osteoblastogenesis and osteo-
clastogenesis, it would seem that dried plum phenolics may
enhance bone formation and inhibit bone resorption, but there
is a problem of these compounds reaching bone cells in vivo,
since they may be poorly absorbed, quickly metabolized in the
liver, or degraded by colon bacteria. However, the chlorogenic
acids from green coffee extract (Farah et al., 2008) were found
in the human plasma at 6μg/mL, and the dose administered
to study subjects was comparable to 100 g of dried plums or
170 mL of prune juice (Table 9; Prior et al., 2007).
Animal Studies
There is substantial research demonstrating that dried plum
can not only prevent but also reverse hormone deficiency-
induced bone loss in rodents, which has been recently reviewed
and summarized (Hooshmand and Arjmandi, 2009). These ani-
mal studies added dried plum powder to a control diet at 5–25%
(w/w) and quantified various parameters of bone metabolism
and architecture after treatment. Ovariectomized female rats are
considered a good model of accelerated bone loss occurring
in postmenopausal women due to an increased rate of bone
turnover and decreased intestinal absorption of calcium. When
the treatment was started immediately after ovariectomy, the
high dose of 25% dried plum powder in the diet prevented the
decrease of bone mineral density of lumbar vertebra and femur
(Arjmandi et al., 2001). These results were recently confirmed
in similar experiment with ovariectomized mice (Rendina et al.,
2009) receiving dried plum powder diets after the operation.
Another study examined the therapeutic effect of dried plum
feeding on pre-existing bone loss. Ovariectomized rats were
allowed to lose bone for 40 days on a control diet before 60-
day treatment with dried plum powder (Deyhim et al., 2005).
Bone mineral density of femur and tibia was restored at the
low dose of 5% dried plum powder, while that of lumbar ver-
tebra improved on 25% dose. The structural and biomechanical
properties were also improved, compared with ovariectomized
controls. A similar study included a positive control group
injected with parathyroid hormone (PTH; Lim et al., 2009).
It was found that dried plum powder partially restored bone
density, strength, and structure, and decreased serum levels of
precollagen I N-terminal propeptide, a marker of bone turnover,
while PTH had no effect on PINP.
Bone loss may also occur due to inactivity (skeletal unload-
ing) in immobilized patients or in astronauts at zero gravity. Such
a study was conducted on rats, which were hindlimb unloaded
for 21 days to induce osteopenia (Smith et al., 2003). It was
followed by 90 days of ambulation with PTH injections or dried
plum powder diet. The bone recovery during re-ambulation pe-
riod was similar on both treatments, resulting in comparable
bone mineral density, bone strength, and bone structure.
1290 M. STACEWICZ-SAPUNTZAKIS
Older men also experience osteoporosis, albeit at a slower
rate than postmenopausal women. Castrated rats provide a
model of male osteoporosis and were therefore investigated us-
ing dried plum powder-supplemented diet (5%, 15%, and 25%;
Franklin et al., 2006). After 90 days treatment, dual energy x-ray
absorptiometry (DXA) scans indicated that bone mineral den-
sity loss of whole skeleton was prevented by the medium and
high doses of dried plum powder. The low dose was effective for
bone mineral density of lumbar vertebra and femur. In another
study, the male rats were castrated and allowed to lose bone for
90 days before the start of dried plum powder diet (25%) or
PTH injections (Bu et al., 2007). The observed reversal of bone
mineral density loss in the whole skeleton and individual bones
was comparable on PTH regime and dried plum powder diet,
and was accompanied by favorable changes in bone structure.
Interesting results were obtained with the mouse model of
age-related bone loss (Halloran et al., 2010). Adult (six months)
and old (18 months) male mice were fed with normal diets or
isocaloric diets containing dried plum powder (15% or 25%,
w/w). After six months on the 25% dried plum diet, the bone
volume increased by 50% in adult and by 40% in the old mice,
while those on control diet lost 24% and 28% bone, respectively.
Thus, dietary plum not only prevented loss but also replaced
bone already lost due to aging. The effects were larger in adult
rather than in old animals. The lower dose of dried plum was
not effective in the old mice and their response to the higher
dose was similar to the response of adult mice on the lower
dose. The effects of dried plum reached a steady state after three
months and further supplementation maintained gain in bone
mass. However, the indices of bone formation, resorption, and
bone mineral density did not vary significantly on different diets.
In order to understand the mechanism of bone-sparing action
of dried plums, various physiological processes, hormones, and
enzymes involved in bone metabolism were studied. When rats
are injected with tritiated tetracycline, it is deposited in bones
and released when bone is resorbed. Subsequent urinary excre-
tion of tritium is a measure of bone resorption. This test was used
to investigate the effect of various food items on bone turnover
in young male rats (Muhlbauer et al., 2003), among them also
“prunes” (7.7% in diet). However, the “prune” powder used in
this survey was a freeze-dried powder made of fresh plums of
unknown variety. It may have had quite different composition
from dried plum powder used in the previously described series
of experiments. After 10 days of feeding, plum powder signifi-
cantly decreased this marker of bone resorption. Similar results
were obtained with dried plum powder in castrated male rats,
using urinary excretion of deoxypyridoline (Dpd), a collagen
degradation product, as a measure of bone resorption (Franklin
et al., 2006). Castrated rats exhibited significantly higher excre-
tion of Dpd, but the dried plum powder (5%) diet reduced it to
normal levels found in intact animals, and higher doses were
even more effective (57% reduction at 25% dose, compared to
control diet). Two bone proteins involved in osteoclastogene-
sis (bone resorption), osteoprotegin, and receptor activator of
NFκ-B ligand were upregulated in castrated rats, but dried plum
powder treatments decreased their expression in the bone in
a dose-dependent manner. Besides decreasing bone resorption,
dried plum powder diets may also stimulate bone formation
through insulin-like growth factor (IGF-I) elevation observed in
both male and female rats. However, serum IGF-I levels were
significantly increased just by the removal of gonads in both
sexes of rats, and the lowest levels were observed in normal
controls on standard diets. IGF-I is supposed to decrease imme-
diately after menopause in women, and to correlate with bone
mass in aging people.
Recently, it was found that freeze-dried blueberry powder
(10% in diet) promoted bone growth in young male and female
rats, which started the ad libitum diet at 20 days of age and
continued it for 14 or 40 days (Chen et al., 2010). Blueberries
contain various phenolic compounds, among them chlorogenic
acid, which was not quantified in the blueberry powder in this
study. However, there was 6–10-fold increase in concentration
of seven phenolic acids in the serum of blueberry-fed rats, the
most prominent being hippuric acid (from 0.5 to 3.3 nM/L).
Both serum of blueberry-fed rats and an artificial mixture of
the seven phenolic acids (at the same concentrations as in the
serum) were able to stimulate osteoblastic cell differentiation
in vitro.
Human Studies
When dried plums (100 g) were consumed by post-
menopausal women (n =18) for 90 days, the serum levels of
IGF-I increased significantly, and so did total alkaline phos-
phatase (AP) and bone-specific alkaline phosphatase (BSAP)
activity, all markers of bone formation (Arjmandi et al., 2002).
The control group (n =20) consumed equicaloric amount of
dried apples (75 g) and also experienced a significant increase
in serum AP. The increase in BSAP activity was not significant
on the dried apple supplement, but the final values after both
treatments were identical. It is possible that dried apples also
exert some beneficial effects, and a crossover trial with the
same group of women could have produced more decisive
results, especially with a control period without any dried fruit
supplement. A three-month study is a short time for human bone
mineral changes, so another trial, involving 100 postmenopausal
women, receiving dried plum (55 subjects) or dried apple (45
subjects) supplements for a whole year, was conducted by
the same group (Arjmandi et al., 2007; Hooshmand et al.,
2011). In addition to biochemical markers in blood samples
collected at 0, 3, 6, and 12 months, DXA measurements of bone
mineral density and bone mineral content were performed at
baseline and end of the study. The consumption of dried plums
preserved bone mineral density of ulna and spine significantly
better than the consumption of dried apple. The effect may
be partially due to suppressing the rate of bone turnover,
as a significant decrease was observed in serum tartrate
resistant acid phosphatase after three months (and maintained
thereafter), and in serum BSAP after 12 months on dried plum
treatment. The dried apple treatment did not produce consistent
changes in biomarkers except an increase in serum osteocalcin.
HEALTH EFFECTS OF DRIED PLUMS AND THEIR PRODUCTS 1291
Calcium Absorption and Bone Health
There may be another mechanism involved in the bone re-
sponse to dried plum feeding. Many sugars were found to en-
hance calcium absorption in the ligated ileum segments of anes-
thetized rats (Vaughan and Filer, 1960). A test solution of la-
beled calcium, 45Ca, and 50 mg of various sugars were injected
into the ligated segments, and the rat femurs were removed af-
ter four hours and checked for radioactivity. Sorbitol increased
the absorption of calcium into the bone by 210%, glucose by
156%, and fructose by 233%. The authors did not find this en-
hancing effect of sugars in the duodenum, where glucose and
fructose are absorbed. Sorbitol is poorly absorbed in the duo-
denum, passes to the ileum, and improves calcium absorption
in the lower regions of the intestinal tract. Another experiment
involved feeding rats for eight weeks on diets containing 20%
sorbitol (Knuuttila et al., 1989). Although no diarrhea was ob-
served, sorbitol-fed rats gain significantly less weight, excreted
more calcium in urine, and retained more calcium in bone.
Their serum calcium level also increased significantly. Bone
resorption on the sorbitol-supplemented diet was also stud-
ied using rats that were pre-labeled with tritiated tetracycline
(Mattila et al., 1996). Sorbitol, 1 mol/kg, i.e., 18.2%, was added
to a basal diet. The rats were maintained on experimental diets
for one month and experienced continuous diarrhea, which de-
creased their weight gain despite a normal rate of food intake.
The excretion of tritium in urine was reduced after one day on
the sorbitol diet and the effect was maintained during the whole
experiment. Radioactivity retained in scapula was significantly
greater on the sorbitol diet, but in the tibia the increase did not
reach statistical significance. These results indicate that sorbitol
supplementation may increase calcium absorption from the in-
testine and suppress bone resorption. This effect could have
been partially responsible for the effects of dried plum powder
diet in previously described animal experiments, since the di-
ets contained from 1 to 6% sorbitol (calculated from sorbitol
content of dried plum powder).
There are some indications that chlorogenic acid and caffeic
acid may stimulate the production of hydrochloric acid in the
stomach of healthy volunteers (Chok and Lang, 1961), who
drank 250 mg of either of these compounds in 200 mL of water.
Quinic acid was not effective in this test. Both regular and
decaffeinated coffee stimulates gastric acid secretion (Cohen
and Booth, 1975; Viani, 1988), probably due to similar content
of chlorogenic acid. It is therefore possible that chlorogenic
acids from dried plums may improve the absorption of calcium
from food and supplements, especially in older persons with
impaired gastric acid production.
Antimicrobial Effects
Dried and fresh plum products have been tested for
the ability to suppress the growth of food-borne pathogens
in liquid broth and ground meat (Fung and Thompson,
2001; Fung and Thompson, 2009). There was a significant sup-
pression of Salmonella typhimurium,Escherichia coli O157:H7,
Listeria monocytogenes,Yersinia enterocolitica, and Staphylo-
coccus aureus in liquid medium and uncooked meat (ground
beef, pork sausage) at a 3–6% concentration of dried plum puree
and fresh plum juice concentrate.
Dried plums may also exert antibacterial action within the al-
imentary and urinary tract because of their unique constituents.
Sorbitol, which is used in control of dental caries as an in-
gredient of chewing gum, has low cariogenicity compared to
sucrose and glucose (Burt, 2006), which are abundant in other
dried fruits and candy. Dental plaque bacteria do not metab-
olize sugar alcohols, so chewing dried plums instead of other
sweets may suppress cariogenic flora. The acids produced by
the dental plaque bacteria demineralize enamel surfaces and
may lead to formation of caries. Phenolic compounds of dried
plums may also interfere with microbial pathogens in the mouth.
The proanthocyanidin fraction of cranberry juice was found to
suppress in vitro the proteolytic action of bacteria responsible
for chronic periodontitis (Bodet et al., 2006). The proteinases
of these bacteria degrade gum and bone tissue in periodontal
pockets.
Interaction of phenolic compounds and nitrite in stomach
may produce nitric oxide, as was found in volunteers after eating
lettuce (source of nitrate) and different polyphenol-rich foods
(apples, berries, onion, cherries, tea, and red wine; Rocha et al.,
2009). Considerable amount of nitric oxide was found in air re-
gurgitated from the stomach during the 30-minute period after
eating these foods. The reaction was confirmed in vitro with
simulated gastric juice, nitrite, and various phenolic compounds
(chlorogenic acid, procyanidin dimers, catechin, epicatechin,
quercetin, and epicatechin-3-O-gallate). Nitric oxide may in-
duce gastric smooth muscle relaxation and kill Helicobacter
pylori. In addition, the adhesion of H. pylori bacteria to stomach
walls may be inhibited by proanthocyanidin polymers (Burger
et al., 2002) as found in vitro with high molecular weight com-
ponent of cranberry juice. It prevented some strains of these
bacteria from binding to human gastric mucus and to a mono-
layer of human gastric epithelial cells in dose-dependent way.
H. pylori infection is associated with stomach ulcers and is a
risk factor for gastric cancer.
Cranberries seem effective in the prevention of urinary tract
infections (UTI), especially in women, and the original hypoth-
esis of their mode of action centered on acidification of urine
(Kinney and Blount, 1979). However, cranberries and their prod-
ucts do not have a reliable acidifying effect (pH 5 and below)
required for bacteriostatic action (Bodel et al., 1959). Never-
theless, both cranberry juice and urine of mice or humans in-
gesting cranberry products were found to inhibit the growth of
bacterial cultures (mostly E. coli, the main culprit in UTI; Sob-
ota, 1984). Fractionation of cranberry extract indicated that the
active components of cranberries were fructose and proantho-
cyanidins, which reduced adherence of bacteria to uroepithelial
cells (Howell, 2007). Both proanthocyanidins and fructose are
present in dried plums and prune juice, but there are no studies
of possible effects of dried plums on UTI prevention. However,
fructose or proanthocyanidins are not found in any significant
amount in urine after cranberry ingestion, but the metabolites of
1292 M. STACEWICZ-SAPUNTZAKIS
proanthocyanidins or other cranberry constituents may be
present in sufficiently high concentration to prevent bacteria
from adhering to urinary epithelium and/or inhibit their growth.
One of these metabolites is hippuric acid, produced from proan-
thocyanidins, chlorogenic acids, and quinic acid, all these com-
pounds being present in prunes and their products. Prune-
making plums contain more quinic acid than cranberries (1.2 vs
0.88 g/100 g), and dried plums have as much as 3.7–4.3 g/100 g
(Kayano et al., 2003a). Consumption of dried plums (300 g)
increased the excretion of hippuric acid in the urine (Blather-
wick and Long, 1923) of a healthy young female subject by
8 g/24 hours. The subject was also tested with an equal weight
(300 g) of cranberries, which produced less than half the amount
of hippuric acid excretion from dried plums. Similar results were
found for a male subject in the same study. There was an increase
in acidity of urine amounting to 0.5 unit of pH in the male and
1.0 unit in the female. In another study, 1.5 g of dried plums per
kilogram body weight per day elevated hippuric acid in serum
and urine of five healthy subjects (Cathcart-Rake et al., 1975).
On an average, 100 g of dried plums increased hippuric acid
excretion by 2.6 g/24 hours, which is in perfect agreement with
the earlier study. In a shorter study, six older women consuming
a single dose of prune juice (315 mL) or dried plums (131 g) ex-
creted on average 0.77 g or 0.24 g of hippuric acid, respectively,
within six hours (Prior et al., 2002).
Although it has not been established that excretion of hip-
puric acid is responsible for the antibacterial effect of cranberries
in the urinary tract, the drug methenamine hippurate (Hiprex) is
still used to prevent recurrent UTI. The hippuric acid moiety was
originally introduced to increase the activity of methenamine,
and the directions still advise eating cranberry and prune prod-
ucts during treatment (RxList, 2013).
Modulation of Immune Response
Certain foods or their constituents may promote wound heal-
ing, alleviate symptoms of autoimmune diseases, or increase
resistance to infection (Hughes et al., 2004). Very little is known
about the effect of dried plums on immune response in vivo. The
addition of prune whip yoghurt (one cup) to the diet was very
effective in healing a persistent varicose ulcer on the leg of a dia-
betic woman, and dermatitis, rash, and itching in other patients,
especially rectal pruritus (Ferrer and Boyd, 1955). However, the
effect may have been partial or whole due to yoghurt, which con-
tained beneficial probiotic bacteria. When chickens were raised
on a standard diet supplemented with freeze-dried powder of
oriental plum (P. salicina) at 1% dose, and infected with cocci-
dosis parasite, they grew better than on the control diet and shed
less oocysts in their feces (Lee et al., 2008). Their spleen lym-
phocyte proliferation was increased even at the 0.5% dose, and
intestinal lymphocytes had an increased expression of mRNA
for interferon-γand interleukin-15 at 1% dose of plum powder.
These results indicate that oriental plum may enhance immune
response in poultry against protozoan infection. However, the
mouse splenocytes proliferation was not enhanced by a similar
freeze-dried powder of oriental plum added to an in vitro culture
(10–500 μg/mL; Lin and Tang, 2007).
On the other hand, there is a need for dietary means to induce
immunosuppression after organ and bone marrow transplanta-
tion (Hushmendy et al., 2009) and in over 80 recognized au-
toimmune diseases. Dried plum powder extracts were tested in
vitro on mouse splenocytes stimulated with concavalin A, and
decreased their production of tumor necrosis factor (TNF-α),
but not of interleukin-6 (Rendina et al., 2009). The extracts also
reduced the production of nitric oxide and cyclooxygenase-2 in
mouse macrophage line RAW264.7 cells, stimulated with bac-
terial liposaccharide, i.e., endotoxin (Kumar et al., 2009). These
results suggest that there may be immunomodulatory properties
to dried plums; however, significantly more research needs to
be done to understand this relationship.
Recent experiments have demonstrated that dietary soluble
fiber (pectin) may have profound effects on the immunologic re-
sponse to endotoxin from E. coli O127:B8 strain (Sherry et al.,
2010). When mice were fed with diet containing 10% pectin
for at least five weeks, and then injected intraperitoneally with
the endotoxin, they became less sick and recovered faster than
mice fed with insoluble fiber (5% or 10% cellulose in diet).
Interleukin-4 production was significantly increased in many tis-
sues, especially in the gastrointestinal tract, of pectin-fed mice,
and the isolated macrophages had an altered cytokine profile.
The authors conclude that dietary pectin changed the T-helper
(Th) cells phenotype to Th2, best suited to neutralization of
bacterial toxins.
Prevention and Suppression of Cancer
Dried plums may exert a direct effect in the gastrointesti-
nal tract, where the cells come in contact with all constituents,
soluble and insoluble, absorbable and non-absorbable, and with
bacterial metabolites of undigested prune constituents in the
colon. Low fecal weight and slow bowel transit time are associ-
ated with increased risk of bowel and rectum cancer (Cummings
et al., 1992). There is a significant correlation of dietary fiber in-
take with stool weight. Dried plums may help to prevent colon
cancer due to their high content of fiber and sorbitol, which
decrease colonic transit time and dilute fecal bile acids by in-
creasing fecal output, and of phenolic compounds, which may
act as antioxidants, preventing DNA damage in colonic epithe-
lium. Binding of bile acids in the intestinal lumen by dietary
fiber and other plant constituents may lower plasma cholesterol
and aid the excretion of cancer-promoting secondary bile acids.
This proposition was studied in vitro using freeze-dried powders
prepared from fresh plums (unknown variety) and dried plums
(Kahlon and Smith, 2007). The samples were digested with ap-
propriate enzymes in a sequence imitating the natural digestion
process, with a mixture of bile acids. Cholestyramine was used
to provide a positive control (100% binding). Both fresh plum
and dried plum powders bound bile acids better than other fruit
powders (except blueberries).
HEALTH EFFECTS OF DRIED PLUMS AND THEIR PRODUCTS 1293
Animal Studies
Colon cancer risk factors were studied in rats fed with
dried plum powder diets (4.75% and 9.5%) and injected with
azoxymethane, a known carcinogen, to induce the formation
of pre-cancerous lesions, referred to as aberrant crypt foci, in
the colon (Yang and Gallaher, 2005). There were two control
groups, one fed with a basal diet, and the other a carbohydrate-
matched diet, with added pectin, fructose, and glucose. There
were no differences among the diets in the number of aber-
rant crypt foci after nine weeks of feeding. The collected fe-
cal samples had lower concentrations of bile acids in dried
plum powder-fed groups, and the daily excretion of bile acids
was also decreased in those rats, although the differences were
not consistently significant and dose-dependent. Colonic bac-
teria were isolated from cecal contents at the end of the ex-
periment and their enzyme activities were assessed. Both 7α-
dehydroxylase (catalyzer of deoxycholic and lithocholic acids
formation from primary bile acids) and β-glucuronidase activi-
ties were decreased in bacteria from dried plum powder-fed rats,
but nitroreductase activity was greatly increased. The lower 7α-
dehydroxylase activity indicates that the dried plum powder diet
may alter colonic bacteria, decreasing their capacity to produce
cancer-promoting secondary bile acids. The other two enzymes
are controversial because they may liberate some carcinogens
or inactivate them, as well as liberate beneficial phytochemicals,
depending on the substrate. The ORAC value of dried plum pow-
der was measured, as well as the ORAC value of cecal contents.
Compared with the basal diet, a low dose of dried plum pow-
der doubled the ORAC value of cecal content (per milliliter),
the high dose tripled it, while carbohydrate-matched diet did not
have any effect. Therefore, the dried plum powder had favorable
effects on antioxidant capacity within the colonic contents, and
possibly decreased the production of cancer-promoting com-
pounds by colonic bacteria. The duration of the experiment
was too short to permit the assessment of the development of
colon tumors from aberrant crypt foci. However, in a similar
experiment with 5% freeze-dried fresh plums (unknown vari-
ety) in the diet, there was a very substantial decrease (86%) in
the total number of azoxymethane-induced aberrant crypt foci
(Boateng et al., 2007), and especially in large foci with more
than four crypts, which are more likely to develop into tumors.
Hepatic glutathione-S-transferase activity was 2.4-fold higher
in the plum-fed rats, compared with the control diet. It is one
of the phase-II metabolizing enzymes and its induction by plum
phytochemicals may facilitate elimination of xenobiotics and
carcinogens from the body.
Cell Culture Studies
In experiments with cell cultures, the extracts from concen-
trated prune juice (125 and 250 μg/mL) reduced viability of
a human colon cancer cell line (Caco-2) and stomach carci-
noma (KATO III) cells, but not that of normal colon fibrob-
lasts (Fujii et al., 2006). An increased apoptosis was observed
in Caco-2 cells incubated with 250-μg/mL extract concentra-
tion. However, 1-mM chlorogenic acid (354 μg/mL) had no
effect on the viability of Caco-2 cells. Fresh plum (P. domes-
tica, cv Arbuznaja) extracts inhibited proliferation of human
colon cancer cells HT29 at 0.05–0.5% concentration (Olsson
et al., 2004). The same group investigated proliferation of breast
cancer cell line, estrogen-dependent MCF-7, and found simi-
lar, but slightly less pronounced effect. Another study evalu-
ated the effect of plum extract and various phenolic fractions
on the proliferation of both MCF-710A (estrogen dependent)
and estrogen-independent MDA-MB-435 breast cancer cells,
along with normal breast epithelial MCF-10A cells (Norrato
et al., 2009). Plum extract was most effective in suppression of
proliferation in estrogen-independent breast cancer cells, while
estrogen-dependent cancer calls were most resistant. Among
phenolic fractions of plum extract, flavonol (quercetin gluco-
side and rutinoside) and proanthocyanidin fractions were most
active. The phenolic acid fraction inhibited proliferation of nor-
mal breast epithelial cells to a lesser degree than other fractions.
Pure chlorogenic acid and neochlorogenic acid inhibited MDA-
MB-435 cell growth by 50% (IC50)at17μg/mL and 10 μg/mL,
respectively, but did not suppress normal cell or MCF-7 cell pro-
liferation up to 60 μg/mL. These concentrations are of the order
found in plasma of healthy volunteers (6 μg/mL) after ingestion
of green coffee extract (Farah et al., 2008). Chlorogenic acid
shows cytotoxicity against human oral tumor cell lines, oral
squamous cell carcinoma (HSC-2), and salivary gland cancer
(HSG), but normal human gingival fibroblasts are much more
resistant (IC50 =1.4 and 1.3 mM vs 2.3 mM, respectively; Jiang
et al., 2000).
Immature fruits of Japanese plum (Prunus salicina Lindl.)
contain a higher level of total phenolics and proanthocyanidins
than mature fruits, so their extracts were used on six differ-
ent human cancer cell lines: Hep G2 (liver), Hela (cervical),
U937 (leukemia), KATO III (stomach), MCF-7, and MDA-MB-
231 (Yu et al., 2007). The extracts were strongly cytotoxic at
0.5 mg/L and 1.0 mg/L concentrations for all cell lines except
MCF-7, while estrogen-independent breast cancer line MDA-
MB-231 was most susceptible due to a very high rate of apop-
tosis (67% at the extract concentration of 0.1 mg/L).
Heterocyclic amines, produced during cooking meat, are car-
cinogenic in laboratory animals, but fruit and vegetable con-
sumption may have a protective effect, especially for the ep-
ithelial cells of digestive tract. Genotoxic effects of 2-amino-1-
methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), the most abun-
dant heterocyclic amine, were investigated in Chinese hamster
lung fibroblast cultures, made susceptible by genetic engineer-
ing (Edenharder et al., 2002). The application of fresh plum
homogenate reduced PhIP-induced DNA damage, assessed by
the comet assay, at concentrations similar to red wine or red
grape homogenate.
Human Studies
Since high intakes of fruits and fiber are associated with
lower incidence of breast cancer, the effect of dried plum
1294 M. STACEWICZ-SAPUNTZAKIS
consumption on estrogen metabolism was investigated in 19
healthy premenopausal women (Kasim-Karakas et al., 2002).
The subjects consumed their usual diet for three menstrual cy-
cles, and dried plums (100 g/day) for the next three menstrual
cycles. Sex steroid hormone metabolites were assessed in their
urine every day. There was a significant decrease in the ex-
cretion of the estrogen conjugates, 2–hydroxyestrone and 16α-
hydroxyestrone, during the luteal phase on the dried plum diet,
but their ratio did not change. The first conjugate is biologically
inactive and does not promote estrogen-dependent breast can-
cer, while the second is considered a risk factor. A high ratio
of the inactive metabolite to the active metabolite is considered
protective against breast cancer.
The presence of inositol in dried plums and their products
may contribute to their protective effects, especially in cell cul-
ture and animal experiments. Supplemental inositol was found
to reduce dysplastic bronchial lesions in smokers (Lam et al.,
2006), albeit at a high dose of 18 g/day. Unexpectedly, it also
reduced their blood pressure after one month of treatment.
The above-described experiments with laboratory animals
and cell cultures indicate that dried plums may be protective
against many forms of cancer due to their high fiber content and
various phytochemicals, which may trigger diverse mechanisms
of detoxification of endogenous and exogenous cancer promot-
ers. Admittedly, many experiments used high concentrations
of phytochemicals that may not be physiologically feasible to
maintain in tissues, except in the epithelium of gastrointestinal
tract.
Diabetes and Atherosclerosis
According to the new international table of glycemic index
(GI) (Foster-Powell et al., 2002) dried plums may be classified
as a low-GI food (GI =29 ±4). Ten healthy subjects were
checked for blood glucose response two hours after consuming
pitted California dried plums (60 g serving, containing 33 g
of available carbohydrates), or glucose. Calculated GI against
white bread was 41, and the glycemic load of such serving was
10 (available carbohydrates multiplied by GI/100). Another de-
termination of GI used larger servings of dried plums (97 g
and 123 g), and calculated that the larger portion contained
50 g available carbohydrates (Glycemic Index Testing Inc.,
2004). The values of GI were 49 for dried plums and 30 for
prune juice. According to the classification proposed by Miller,
low GI values are less than 55 (Foster-Powell et al., 2002).
Low-GI foods are more satiating than high-GI foods, and do not
cause large postprandial rise and fall in blood insulin. Therefore,
low-GI foods are recommended for managing diabetes and for
weight control. The high content of sorbitol in dried plums may
be partly responsible for their low GI. Sorbitol has a very low
GI of 9, and a meal composed of glucose and sorbitol yielded
a glycemic load smaller than predicted from the sum of indi-
vidual loads, possibly due to decrease of glucose absorption in
presence of sorbitol (Livesey, 2003).
Dried fruit consumption (at least 1 oz/day) was associated
with reduced abdominal obesity and reduced the risk of being
overweight or obese (BMI >25 kg/m2) in adults, as seen in the
NHANES, 1999–2004 population data base (Keast and Jones,
2009). The short-term effect of the addition of dried plums
to a snack was studied in 45 healthy, normal weight subjects
(Farajian et al., 2010) in a controlled laboratory setting. The
subjects ate a standardized breakfast and two hours later took
a snack of bread, cheese, and five dried plums. Three hours
later they received lunch and dessert, consumed ad libitum. The
experiment was repeated with the same subjects receiving an
equicaloric snack of bread and cheese. The subjects had sig-
nificantly smaller energy intake during lunch when dried plums
were included in the snack, and ate less dessert (chocolate cake).
Their feeling of satiety was higher at all points between the
snack and lunch. Dried plums were also evaluated against low-
fat cookies in 19 fasting adult women who ate them as a snack
two hours before a test meal (Furchner-Evanson et al., 2010).
The rise of plasma glucose and insulin after the dried plum snack
was lower than after cookies and the satiety index was higher.
In another study by the same group (Howarth et al., 2010),
29 women had two snacks daily for two weeks, consisting of
dried plums (100 kcal, 42 g servings), and equicaloric snacks of
low-fat cookies for another two weeks (randomized, crossover
trial with washout period). Plasma triglycerides were signifi-
cantly lower after dried plum consumption than after cookies,
and the intake of fiber, potassium, riboflavin, niacin, and calcium
was significantly greater.
In the Los Angeles Atherosclerosis Study (n =500), a sig-
nificant association was observed between the progression of
atherosclerosis (measured ultrasonographically by the intima-
media thickness of carotid arteries) and the intake of pectin (Wu
et al., 2003). Triglyceride levels and the ratio of total choles-
terol to HDL–cholesterol were inversely related to the total fiber
intake, assessed by repeated dietary recalls.
Another component of dried plums, chlorogenic acid, signifi-
cantly lowered plasma concentrations of cholesterol and triglyc-
erides when infused intravenously into obese, hyperlipidemic,
and insulin-resistant rats (Rodriguez de Sotillo and Hadley,
2002). The rats were infused with chlorogenic acid (5 mg/kg
BW/day) or saline solution for three weeks. The control rats
gained two-fold more weight during this time than the treated
rats. There was a significant decrease in the liver triglycerides
of chlorogenic acid-infused rats and their postprandial peak of
blood glucose was significantly reduced.
Early in vitro experiments with chlorogenic acid indicated
that it may decrease glucose active transport across intestinal
brush border and inhibit production of glucose in the liver frac-
tions (reviewed by Stacewicz-Sapuntzakis et al., 2001). More
recent experiments on human intestinal Caco-2 cells found that
apple extracts decreased glucose uptake and transport in Caco-2
cell monolayers due to the presence of polyphenols and phe-
nolic acids (Manzano and Williamson, 2010). The apple ex-
tracts contained considerable concentration of chlorogenic acid
(0.33 mM), which was found responsible for 12% of glucose
transport inhibition activity.
HEALTH EFFECTS OF DRIED PLUMS AND THEIR PRODUCTS 1295
A trial with healthy volunteers consuming glucose with caf-
feinated or decaffeinated coffee, both containing 354-mg chloro-
genic acids, suggested that caffeine in coffee may impair glu-
cose tolerance, while chlorogenic acids have the opposite effect
(Johnston et al., 2003), as indicated by gastrointestinal hormone
profiles. These incretin hormones were assayed in blood sam-
ples along with glucose and insulin, and their kinetics were
consistent with delayed glucose absorption in the distal portion
of small intestine after drinking decaffeinated coffee. A simi-
lar experiment with healthy subjects involved drinking a dose
of 25 g sucrose with chlorogenic acid-enriched coffee prod-
uct (600-mg chlorogenic acids), caffeinated or decaffeinated
coffee, in a crossover design (Thom, 2007). Only the chloro-
genic acid-enriched coffee significantly decreased plasma glu-
cose elevation within two hours compared with control (su-
crose solution in water). The same publication reports another
study with 30 overweight subjects (BMI: 27.5–32 kg/m2), who
were drinking five cups a day of instant coffee or the chloro-
genic acid-enriched coffee product (600-mg chlorogenic acids
per day) for 12 weeks. The increased intake of chlorogenic
acids was associated with a significant decrease in body weight
(5.4 ±0.6 kg) and body fat (3.6 ±0.3%).
The addition of dried plum extract (25% w/w) to the diet of
stroke-prone spontaneously hypertensive rats significantly de-
creased their systolic blood pressure after a five-week treatment,
compared to basic diet (Negishi et al., 2007). Smooth muscle
cells were isolated from the aorta of these rats, incubated with
caffeic acid, and challenged with angiotensin II. Their superox-
ide content decreased to control levels (without angiotensin) due
to caffeic acid treatment. Dried plum powder was used in a study
of atherosclerosis in apolipoprotein E-deficient mice (Gallaher
and Gallaher, 2009). These mice quickly develop atheroscle-
rotic lesions on diet containing cholesterol and saturated fat.
For 20 weeks, they were fed with a basal diet, cholesterol diet
(0.15%), and cholesterol diet with 4.75% or 9.5% dried plum
powder. There was no effect of dried plum treatment on plasma
cholesterol or triglyceride concentrations compared to choles-
terol diet, but the atherosclerotic lesions in the aortic arch and ar-
terial trees were significantly reduced by the lower dose of dried
plum powder. Serum amyloid P-component (SAP), a systemic
marker of inflammation in mice, was doubled in cholesterol-rich
diet group, but the effect of cholesterol disappeared when dried
plum powder was added. Interestingly, the higher dose was not
more effective than the lower dose for any measured parameter
in this study.
Similar studies with other species of plums (Asian apricot P.
mume and Japanese plum P. salicina) deserve consideration, al-
though relative proportions of various phytochemicals in these
fruits differ from dried plums (P. domestica), and the experi-
ments were conducted with fresh fruit extracts or concentrated
juice. When insulin-resistant obese rats and diabetic mice were
given Asian apricot juice concentrate (ekisu, made from the
fruit of P. mume) in drinking water, their glucose tolerance im-
proved significantly after two weeks of treatment (Utsunomiya
et al., 2005). Their plasma levels of adiponectin increased, and
mRNA expression of PPARγin adipose tissue was enhanced.
The treatment prevented the rise of total plasma cholesterol and
triglyceride during the treatment, which occurred in the un-
treated obese rats. The same juice concentrate inhibited in vitro
the angiotensin II-induced protein synthesis in vascular smooth
muscle cells prepared from the aorta of normal rats (Utsunomiya
et al., 2002). It may indicate a protective action of ekisu against
vascular hypertrophy and high blood pressure. Phenolic extracts
from Black Splendor plum (P. salicina) were effective in de-
creasing oxidative stress induced by 10-mM glucose in human
umbilical vein endothelial cell cultures (Townsley et al., 2009)
as indicated by the decrease in inflammatory biomarkers IL-6
and IL-8 and transcription factor NF-κB.
Oxidized lipids engulfed by macrophages in endothe-
lial walls produce atherosclerotic plaque. When mouse
macrophages RAW264.7 were stimulated in vitro with FeSO4
and H2O2, the extracts of dried plum phenolics reduced their
malonaldehyde production (an indicator of lipid peroxidation)
(Kumar et al., 2009).
Iron Absorption
High content of phenolic compounds in fruit juices inhibits
the intestinal iron uptake by forming irreversible complexes,
while ascorbic acid promotes iron absorption. Among different
fruit juices, red grape and prune juices were found to inhibit the
absorption of soluble iron in Caco-2 cell model combined with
in vitro digestion (Boato et al., 2002). Caco-2 cell ferritin for-
mation was used as the marker of iron uptake and it decreased
31% by prune juice and 67% by red grape juice. Although the
effect of prune juice was not statistically significant, the authors’
suggestion was to limit the intake of both juices in infants and
in other conditions of iron insufficiency, but to increase it for
people at risk of hemochromatosis. There are some indications
that many degenerative diseases, as well as the toxicity of many
compounds, involve poorly bound iron, producing hydroxyl rad-
icals (Kell, 2010). Therefore, iron-chelating dietary compounds
present in dried plums may prevent or inhibit the progression of
cellular insults caused by iron overload.
Neurologic and Psychiatric Effects
Recent experiments with aging laboratory animals indicated
that high intake of various fruit or vegetable extracts were effec-
tive in reversing neurochemical and behavioral changes associ-
ated with decline in cognitive performance. Dried plum powder
and plum juice prepared from fresh prune-making plums were
used in a study of 19-month-old rats (Shukitt-Hale et al., 2009).
The animals were already showing neurologic decrements by 15
months of age. One group of rats had dried plum powder added
to a standard diet at 20 g/kg (2%), while another group was
drinking plum juice instead of water. Both groups and control
groups were tested after eight-week treatment using the Morris
water maze, where they learned to find a submerged platform
in a circular pool. Latency (time to find the platform) and the
1296 M. STACEWICZ-SAPUNTZAKIS
Tab le 1 3 Potential health effects of dried plum components
Potential health effects
Immune Neural &
Dried plum components Laxative Gastrointestinal Anti-cancer Cardiovascular Anti-diabetic Bone Anti-bacterial function cognitive
Dietary fiber •• • •
Sorbitol •• • •
Inositol
Phenolic compounds •• • •
Quinic acid
Vitamin K1 ••
Boron •• •
Copper ••
Potassium ••
distance traveled to find it were the measures of improved work-
ing memory. Both measures were significantly shorter for plum
juice-drinking rats, which indicated improvement of memory
and faster learning. The dried plum powder diet had no effect
on cognitive performance, possibly because it delivered much
less antioxidants than plum juice (3.3-mg GAE/day vs 30.3-
mg GAE/day), and some antioxidants are destroyed during the
preparation of dried plum powder, which is more extensive than
that of plum juice. Serum of rats consuming plum juice had
significantly higher ORAC values, while that of dried plum
powder-treated rats was not different from the controls.
The main constituent of dried plum phenolics, chlorogenic
acid, was investigated in mice using exploratory tests for anxiety
and neophobia (Bouayed et al., 2007). However, chlorogenic
acid was injected intraperitoneally, bypassing absorption and
colonic degradation. At 20 mg/kg BW chlorogenic acid caused
a decrease in anxiety-related behavior, i.e., the treated mice were
more likely to investigate unfamiliar and well-lit environment.
Previously, the same group found that there is positive correla-
tion between peripheral blood granulocyte oxidative status and
level of anxiety in mice. Therefore, they used mice granulocytes
to evaluate the chlorogenic acid effect on oxidative stress gen-
erated by the addition of H2O2in vitro and found that 0.5-mg
chlorogenic acid was equivalent to 0.12 mg of vitamin C.
Interestingly, serotonin, a neurotransmitter, which decreases
anxiety and neophobia, was found in red, blue–red, and blue
plums of unspecified varieties (3.6–5.7 μg/g; Feldman and Lee,
1985), but there are no data for dried plums. Serotonin is well ab-
sorbed into circulation, but apparently cannot cross brain blood
barrier, so the ingested serotonin should not affect the behav-
ior and cognition. Another component of dried plums, inositol,
has been investigated in treatment of various psychiatric dis-
orders (Levine, 1997). Inositol is a source of several second
messengers in brain and its content is reported to be decreased
in cerebrospinal fluid in depression. Significant therapeutic ef-
fects of inositol supplementation were found in depression and
panic disorder (dose of 12 g/day), and in obsessive-compulsive
disorder (18 g/day). Inositol was not helpful in schizophrenia,
Alzheimer’s disease, attention deficit disorder with hyperac-
tivity in children, autism, or electroconvulsive therapy-induced
memory impairment. All trials had a double-blind crossover de-
sign with placebo (glucose) and included 9 to 28 patients. The
investigators concluded that inositol may be beneficial in dis-
eases responsive to serotonin selective re-uptake inhibitors. An
increased dietary intake of inositol may also have a therapeuti-
cal potential in the treatment of diabetic neuropathy, delaying
the onset or improving sensory nerve function. Such improve-
ment was reported in 20 diabetic patients when the total mean
daily intake of inositol was increased from 0.77 to 1.65 g/day
(Clements, 1980). According to the data in Table 2, moderate
servings of dried plums or prune juice could deliver physiolog-
ically significant amounts of inositol.
High-antioxidant fruit extracts were also found to decrease
the toxic effects of dopamine or amyloid β-peptide in transfected
COS-7 cell model (Joseph et al., 2004). Dried plum (0.5 mg/mL)
extract significantly improved viability of dopamine-treated
cells and regulation of calcium fluxes in amyloid β-peptide-
treated cells. The authors surmised that fruit intake may pro-
vide some protection against neuronal aging and Alzheimer’s
disease.
SUMMARY AND FURTHER RESEARCH
RECOMMENDATION
During the last decade (2000–2010) there has been a con-
siderable progress in discovering and understanding of health
effects related to the consumption of dried plums. Table 13 at-
tempts to summarize the possible effects in the form of a grid,
although more accurate representation may be that of a com-
plicated web, since many health effects are interrelated and the
dried plum components may act in synergy. Increasingly, health
professionals are urged to focus on whole foods, rather than in-
dividual nutrients (Mozzaffarian and Ludwig, 2010), as dietary
targets in order to design more effective strategies for the pre-
vention of chronic diseases. Dried plums are a whole, minimally
processed food, belonging to a traditional, time-tested way of
eating in many populations. Recent studies on replacing other
snacks with dried plums indicate many beneficial health effects
besides increasing satiety and reducing desire for sweetened
HEALTH EFFECTS OF DRIED PLUMS AND THEIR PRODUCTS 1297
Tab le 1 4 Future research recommendations
Composition studies
Assessment of all constituents of fresh prune-making plums to investigate changes occurring during processing by comparing fresh and dried plums.
Assessment of individual sugars, vitamin B6, and iron in prune juice (discrepancy in USDA SR 25 with the data inferred from dried plums).
Analysis of phenolic compounds in fresh plums d’Agen, dried plums, and dried plum powder using phloroglucinolysis and/or thiolysis to assess
proanthocyanidins content and type.
Assessment of serotonin content in dried plums and prune juice.
Cell culture studies
Experiments on the cells of gastrointestinal tract (normal and cancer cell lines, preferably human) with extracts and homogenates of dried plums (viability,
absorption of nutrients and bioactive compounds).
Experiments on the cells involved in bone maintenance, atherosclerosis, diabetes, various cancers, or cognition, with identified metabolites of dried plum
phenolic compounds.
In vitro experiments with urine of animals or humans on dried plum diet: assessment of bacteriostatic action of urine on UTI-causing strains and their
adhesion to urinary epithelial cells, hippuric acid, and other metabolites of dried plum constituents in urine.
In vitro study of H. pylori suppression and adhesion to stomach epithelial cells or gastric mucus by prune juice or dried plum homogenates.
Animal studies
Repetition of animal experiments involving bone preservation, cognitive decline, immune response, atherosclerosis, and cancer with diet containing a
powder made of dried plums by technologies less destructive to antioxidants, or prune juice replacement of drinking water.
Animal experiments on absorption of iron while drinking prune juice (assessed for the content of iron, vitamin C, and phenolic compounds) with a control
diet or drink containing the same amount of iron and vitamin C. Blood iron parameters should be measured and compared in both groups.
Human studies
Intervention trial of a few healthy subjects on controlled diet to study the metabolism of phenolic compounds from dried plums: a washout period of
commercial liquid diet and water, followed by a period of liquid diet and dried plums (100 g/day) with collection of blood samples, urine, and feces for
analysis.
Intervention study to check production of nitric oxide in stomach and changes in colonic flora after eating dried plums or drinking prune juice.
Intervention trial (crossover design) of subjects prone to UTI with a daily supplement of dried plums or prune juice (negative control – no dietary
intervention; positive control – cranberry juice or sauce), and collection of urine samples for in vitro experiments and analysis.
food, very important factors in controlling overeating, obesity,
diabetes, and related cardiovascular diseases.
Dried plums contain unique constituents in characteristic
amounts and proportion, which are not found in common foods,
even in other dried fruits. These are listed in Table 13, while other
tables report their content in dried plums and their products. The
combination of dietary fiber, sorbitol, and chlorogenic acids may
be responsible for many beneficial gastrointestinal effects, in-
cluding prevention of constipation, dental caries and gingivitis,
stomach ulcers, and colon cancer. The metabolites of quinic acid
and specific phenolic compounds (chlorogenic acids and proan-
thocyanidins) may also act as bacteriostatic agents in prevention
of UTI. Phenolic compounds are implicated in all listed poten-
tial health effects, including anti-diabetic action, cardiovascular
benefits, bone preservation, improved immune function, and
mitigating neural/cognitive defects. The relatively high content
of phylloquinone (vitamin K1) may be important for cardio-
vascular health, bone metabolism, and glucose/insulin regula-
tion, working synergistically with boron and copper, which are
also abundant in dried plums. Western diet is characterized by
low intake of potassium and overly high intake of sodium, es-
pecially from processed foods, therefore potassium content of
dried plums may be beneficial for cardiovascular system and
bone maintenance. The presence of inositol may also aid car-
diovascular health, as well as neural and cognitive function.
Much progress was recently achieved in the investigation of
therapeutic effects of dried plums on bone turnover, with nu-
merous mechanistic studies on animals and cell cultures. How-
ever, it is still unknown which individual compounds, alone
or in combination, produce the observed effects. The presence
of phenolic metabolites in circulation is still very controver-
sial, with some researchers finding significant concentrations of
possibly active metabolites of chlorogenic acids and others re-
porting negative results. The difficulties of measuring phenolic
compounds are also encountered in the analysis of dried plum,
with unresolved question of proanthocyanidin content, which
are possibly a major fraction. The problem of physiologically
significant concentrations of active metabolites reaching target
tissues is of vital importance in the investigation of potential
preventive and therapeutical effects.
In conclusion, this review summarizes further research rec-
ommendations in Table 14, in hope that it will help the re-
searchers to direct their investigations on the elucidation of
health effects of dried plums.
ACKNOWLEDGMENTS
The author is grateful to Drs George C. Fahey, Daniel Y.
C. Fung, and Frederick Khachik for permission to quote their
research findings reported to California Dried Plum Board.
Addendum
After completion of the preceding manuscript, an important
study on mineral and vitamin content of dried fruits has been
published in 2011 (Bennett et al., 2011). Dried plums d’Agen
originated from three different countries, Australia, Chile and
1298 M. STACEWICZ-SAPUNTZAKIS
the U.S. Some of the results are shown in the table below. Com-
parative values from USDA, 2012 (SR 25) are also included.
Micronutrient per
100 g dried plums Australia Chile California, USA
USDA,
2012 SR 25
B, mg 2.04 3.18 1.96
Ca, mg 42.938.837.243
Cu, mg 0.37 0.30 0.27 0.28
Fe, mg 3.18 2.08 2.12 0.93
K, mg 746.6 815.0 766.0 732
Mg, mg 32.939.841.341
Mn, mg 0.96 0.92 0.90 0.30
P, mg 5 7.279.472.969
Se, mg 0.00 0.24 0.00 0.3
Zn, mg 1.15 0.43 0.32 0.44
Folate, μg29.721.819.84
Adapted from Bennett et al., 2011.
It is interesting to notice the high zinc content in Australian
dried plums (10% DRI, see Table 3). The results for iron and
manganese in the U.S. dried plums were much higher than re-
ported in SR 25, and would deliver 12% and 39% DRI, respec-
tively, in a 100 g serving. While vitamin C was not detected in
any of the samples, folate content was quite high (5 -7.5% DRI).
It is possible that the difference is due to the methodology em-
ployed for the determination of folate in dried plums, although
it seems that microbiological methods were used in both investi-
gations (Bennett et al., 2011 and USDA, 2012). Microbiological
assays of folate are prone to very high inter-laboratory variabil-
ity, therefore the direct HPLC analysis is much recommended
(Koontz et al., 2005). Repeated analysis of iron and manganese
should also be conducted.
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... Prunes have been historically consumed for their purported gastrointestinal health benefits (45) and are a rich source of potassium, boron, copper, vitamin K, and phenolic compounds, such as chlorogenic acids, phenolic acids, and flavonoids (45,46), which have antioxidant properties (47). Compared with prune juice, prunes have a higher content of dietary fiber and vitamins A and K, and total oxygen radical absorbance capacity. ...
... Prunes have been historically consumed for their purported gastrointestinal health benefits (45) and are a rich source of potassium, boron, copper, vitamin K, and phenolic compounds, such as chlorogenic acids, phenolic acids, and flavonoids (45,46), which have antioxidant properties (47). Compared with prune juice, prunes have a higher content of dietary fiber and vitamins A and K, and total oxygen radical absorbance capacity. ...
... Compared with prune juice, prunes have a higher content of dietary fiber and vitamins A and K, and total oxygen radical absorbance capacity. Furthermore, prunes have a higher content of total phenolics compared with fresh plums (45). Overall, prunes are considered a promising functional food for improving bone health and the bioactive components are thought to act synergistically within the whole food matrix to maintain bone health after menopause (39,48). ...
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... Thus, the terms used to refer to dried sour plums differ. The term prune or plum is used by Chinese, Japanese, and Korean for the ume plum (Prunus mume), which is more similar to apricot than plums (Stacewicz-Sapuntzakis, 2013). ...
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... Plums are fruits rich in polyphenols such as proanthocyanidins, flavonoids, hydroxycinnamic acids and coumarins, and in some countries these fruits-which exhibit a great diversity in shape, size, appearance and taste-are used as medicinal products [5,6]. The global annual production of plums is approximately 11,000,000 tons, and they are marketed worldwide, with the highest demand in Europe, North America and Japan [7]. ...
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... Thus, drying has the ability to extend the shelf life of food materials. The consumption of the dried plum may lower the risk of chronic diseases and relieve constipation and this effect is mainly associated with biologically active substances like phenolic compounds, carotenoids, vitamin C and dietary fibre that are naturally present in fruit (Stacewicz-Sapuntzakis, 2013). With increased awareness of food nutrition and health, consumers have become more selective and challenge the researchers to develop ways for creating high quality dried commodities (Saga and Suresh, 2010). ...
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Novel functional foods have recently emerged to satisfy the demand for healthy and nutrient dense foods with biological potential. The Mediterranean diet is well known for being rich in vegetables, fruits, nuts and olive oil products. Herein, we discuss recent functional foods with biological activities such as antioxidant, anti-inflammatory, immunomodulatory, prebiotic and modulatory of the gut microbiota. This chapter includes novel functional foods prepared from dried fruits such as raisins, dates, figs and plums. The nuts are also recognized as food with functional properties and are represented by pine nuts, tiger nuts, almonds and pistachios. Drinks from Mediterranean region in addition to legumes products of carob, fenugreek and fava beans are also included. Further, metabolic and/or chemical profiling, physiochemical properties are reported for these functional products. The reported phytoconstituents include flavonoids, proanthocyanidins, phenylethanoids, phenolic acids and stilbenoids. Also, proteins, dietary fibers and peptides proposed from these plant products are also discussed.
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Prunus domestica - is one of the main fruit crops in Ukraine with a production of about 200 tons per year. In the world over then 2000 varieties of this plant are grown. In Ukraine, the following varieties of plums are zoned: Anna Shpet, Renklod Altana, Ugorka Stanley, Ugorka Italian, Ugorka Azhanska, and others. This plant is the valuable source of polysaccharides and phenolic compounds. That is why plum fruits are a part of many dietary supplements with laxative and anti-inflammatory activity in treating chronic constipation. In our previous research, we studied the chemical composition of alcohol extracts and polysaccharide complex of plum fruits. Following types of pharmacological activities: diuretic, membrane stabilizing, anticoagulant laxative, hepatoprotective, were confirmed in the analysed substances. In the article, we present the results of a study of the chemical composition of the plum presscake that remained after the plum juice was obtained. The composition of phenolic compounds was analyzed by using TLC, SF and HPLC methods. Antimicrobial activity of the alcohol extract of plum presscake was investigated by agar diffusion method. The results obtained indicate the possibility of complex processing of raw materials and obtaining new antimicrobial drugs from the presscake of plum juice production.
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The objective of the present study was to develop sweetened stirred fruit yoghurt incorporated with plum fruit pulp. The pulp was added @ 10, 15 and 20% and the formulated sweetened fruit yoghurt was studied for various physico-chemical (pH, acidity, syneresis, and tyrosine value) and organoleptic characteristics during storage. Plain (natural) and plum yoghurt were observed significantly different and the results showed a significant (p<0.05) decrease in pH and increased acidity, syneresis, and tyrosine value among various treatments and during storage. The addition of plum fruit in natural yoghurt modified the sensorial characteristics of the formulated product. Fruit yoghurt prepared by the addition of plum at 10% level was most acceptable with significantly improved sensory characteristics and shelf life of 12 days during refrigerated storage.
Article
Globally, commercialized plum cultivars are mostly diploid Chinese plums (Prunus salicina Lindl.), also known as Japanese plums, and are one of the most abundant and variable fruit tree species. To advance Prunus genomic research, we present a chromosome‐scale P. salicina genome assembly, constructed using an integrated strategy that combines Illumina, Oxford Nanopore, and high‐throughput chromosome conformation capture (Hi‐C) sequencing. The high‐quality genome assembly consists of a 318.6 Mb sequence (contig N50 length of 2.3 Mb) with eight pseudochromosomes. The expansion of the P. salicina genome is led by recent segmental duplications (SDs) and a long terminal repeat (LTR) burst of ~0.2 Mya. This resulted in the significant expansion of gene families associated with flavonoid metabolism and plant resistance, which impacted fruit flavor and increased species adaptability. Population structure and domestication history suggest that Chinese plum may have been originated from South China and provides a domestication route with accompanying genomic variations. Selection sweep and genetic diversity analysis enabled the identification of several critical genes associated with flowering time, stress tolerance, and flavonoid metabolism, demonstrating the essential roles of related pathways during domestication. Furthermore, we reconstructed and exploited flavonoid‐anthocyanin metabolism using multi‐omics analysis in Chinese plum and proposed a complete metabolic pathway. Collectively, our results will facilitate further candidate gene discovery for important agronomic traits in Chinese plum and provide insights into future functional genomic studies and DNA‐informed breeding.
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It is now widely appreciated that nutrition contributes significantly to the optimal working of the immune system and hence to personal health. In Diet and Human Immune Function, leading international researchers and clinicians comprehensively detail what is known about the ability of diet to enhance human immune function in health, disease, and under various conditions of stress. The authors offer state-of-the-art critical appraisals of the influences on the human immune system of several important vitamins (vitamins A, C, and E, as well as carotenoids, such as b-carotene) and minerals (iron, selenium, and zinc), both singly and in combination. The authors also examine how nutrition modulates immune function in such disease states as rheumatoid arthritis, osteoporosis, HIV infection, and cancer. Immune responses to three forms of stress-vigorous exercise, military conditions, and air pollution (in relation to allergic asthma)-are discussed in depth in unique chapters not found in any other texts. Probiotics and long-chain fatty acids are also examined for their immunomodulatory effects. A much-needed overview of the nutritional consequences of drug-disease interactions provides recommendations for potential nutritional interventions that could increase drug efficacy and/or reduce adverse side effects. "Conclusions" and "Take Home Messages" at the end of each chapter give physicians clearly stated clinical instructions about special diets and dietary components for immune-related disease states. Authoritative and highly practical, Diet and Human Immune Function provides a critical survey of the most up-to-date clinical studies of nutritional effects on immune responses for disease prevention and therapy, documenting for practicing physicians, nutritionists, immunologists, and educated consumers the enormous potential of diet to modulate immune function beneficially.