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Potential Nutritional Benefits of Current Citrus Consumption

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  • Physicians Association for Nutrition

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Citrus contains nutrients and phytochemicals that may be beneficial for health. We collected citrus production and consumption data and estimated the amount of these compounds that are consumed. We then compared the amounts of citrus and citrus-derived compounds used in studies that suggest a health benefit to the amounts typically found in citrus. Data is scarce, but suggests that citrus consumption might improve indices of antioxidant status, and possibly cardiovascular health and insulin sensitivity.
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Agriculture 2013, 3, 170-187; doi:10.3390/agriculture3010170
agriculture
ISSN 2077-0472
www.mdpi.com/journal/agriculture
Review
Potential Nutritional Benefits of Current Citrus Consumption
Tami Turner 1 and Betty J. Burri 2,*
1 Department of Nutrition, University of California, Davis, One Shields Avenue, Davis, CA 95616,
USA; E-Mail: tturner@ucdavis.edu
2 Western Human Nutrition Research Center, ARS, USDA, 430 W Health Sciences Drive, Davis,
CA 95616, USA
* Author to whom correspondence should be addressed; E-Mail: betty.burri@ars.usda.gov;
Tel.: +1-530-752-4748; Fax: +1-530-752-4390.
Received: 30 November 2012; in revised form: 1 February 2013 / Accepted: 17 February 2013 /
Published: 19 March 2013
Abstract: Citrus contains nutrients and phytochemicals that may be beneficial for health.
We collected citrus production and consumption data and estimated the amount of these
compounds that are consumed. We then compared the amounts of citrus and citrus-derived
compounds used in studies that suggest a health benefit to the amounts typically found in
citrus. Data is scarce, but suggests that citrus consumption might improve indices of
antioxidant status, and possibly cardiovascular health and insulin sensitivity.
Keywords: citrus; vitamin C; vitamin A; carotenoid; flavonoid; limonoid; health; human
1. Introduction
Citrus is the largest genus in the family Rutaceae and is the most traded horticultural product in the
world [1]. Taxonomic identification is difficult because there are many spontaneous and commercial
hybrids, but citrus can be generally classified into the following categories: sweet oranges (most are C.
sinensis but also includes blood and acidless oranges), mandarins (such as Satsuma (C. unshi),
tangerines (C. tangerina, and reticulata), and clementines (C. clementine)), sour/bitter oranges (such as
Seville, C. aurantium), lemons (C. limon), limes (C. aurantifolia and latifolia), grapefruit (C. paradisi)
and pummelos (C. grandis), hybrids (e.g., tangelos, tangors, and limequats), and citrons (C. medica,
which has a rind that is used primarily for confectionary and is only commercially grown in limited
areas) [2].
OPEN ACCESS
Agriculture 2013, 3 171
Diets rich in fruits and vegetables have been strongly associated with numerous health benefits and
lower risk of disease [3,4]. Citrus fruits contain a variety of vitamins, minerals, fiber, and
phytochemicals such as carotenoids, flavonoids, and limonoids, which appear to have biological
activities and health benefits. There is considerable evidence that citrus fruit have antioxidant and
antimutagenic properties and positive associations with bone, cardiovascular, and immune system
health [5].
2. Data Sources
Production and consumption data were used to estimate the amounts of nutrients and non-nutrient
components of citrus fruits that are consumed. Data for production and estimated consumption was
compiled from databases maintained by the U.S. Department of Agriculture (USDA) and the Food and
Agriculture Organization of the United Nations (FAO). U.S. data on the amount of nutrients in citrus
consumed/capita/day and the percentage of the total dietary nutrient intake from citrus was taken directly
from USDA data [6]. Nutrient and non-nutrient concentrations of citrus fruit were gathered from
published literature and from the USDA. Then nutrient concentration ranges reported in 100 g of citrus
were compared to the RDA or AI (based upon age and life stage) for that nutrient. We reviewed the
literature for health benefits of whole citrus fruits, for those nutrients and phytochemicals that are
derived primarily from citrus fruit or that are present in citrus varieties in high concentrations by
searching the electronic databases PubMed, Web of Science, and Agricola using keyword and phase
searches such as “citrus and health”, “citrus and cardiovas*”, “carotenoid and citrus”, “flavonoid and
citrus”, etc. The amounts of nutrients and phytochemicals typically reported in citrus fruit were
compared to the amount of citrus or citrus-derived nutrients used in studies that showed health benefits.
Barriers to citrus consumption and trends in the citrus industry were identified through online
government databases from the USDA Economic Research Service, National Agriculture Statistical
Service, and Economic Statistics and Market Information System, as well as from university extension
and citrus supplier websites.
3. Production and Consumption
In 2010, the production of citrus fruit worldwide was estimated as 122.5 million tonnes with
~8.7 million hectares harvested; oranges were 50%–62% of the total area harvested and total
production [7] (Figure 1). Worldwide, there has been a steady increase of estimated per capita
consumption of citrus over the last 30 years (Table 1). However, least developed countries located in
areas of Sub-Saharan Africa and Southeast Asia, which generally have the highest proportion of persons
with malnutrition and micronutrient deficiencies [8–10], also have the lowest consumption of citrus.
Despite the growth of the citrus industry in China [6,7], people in lower income countries of Africa and
Asia consume approximately one-fourth as much citrus as developed countries. In fact, populations in
least developed countries consume only 8 g/person/day, six times less than the world average. On the
other hand, with the high production of citrus in the U.S., Mexico, Brazil, and Spain it is not surprising
that North Americans have the highest estimated consumption/capita/day in the world followed by
South Americans and Europeans [11].
Agriculture 2013, 3 172
Figure 1. World production of citrus by fruit type in 2010 [7].
Table 1. Estimated supply and consumption of citrus by region, per person per day, and the
percentage of citrus consumed that is oranges and mandarins 1979–2009 [11].
Region Item 1979 1989 1999 2009
World Total citrus supply tonnes 49,114,005 67,645,354 89,146,403 112,910,151
Total citrus g per capita/day 32 36 42 47
% of total that is oranges & mandarines 78 81 76 72
Least Total citrus supply tonnes 718,199 918,998 1,358,035 2,182,861
Developed Total citrus g per capita/day 6 6 7 8
Countries % of total that is oranges & mandarines 33 33 43 50
Africa Total citrus supply tonnes 4,371,141 5,955,141 8,312,179 10,988,040
Total citrus g per capita/day 26 28 31 32
% of total that is oranges & mandarines 50 54 52 50
Asia Total citrus supply tonnes 4,371,250 5,955,256 8,312,304 10,988,172
Total citrus g per capita/day 12 18 23 31
% of total that is oranges & mandarines 83 78 78 71
SE Asia Total citrus supply tonnes 991,627 1,695,364 3,008,770 4,947,774
Total citrus g per capita/day 7 10 16 24
% of total that is oranges & mandarines 100 100 81 83
Oceania Total citrus supply tonnes 515,315 569,112 547,564 548,025
Total citrus g per capita/day 73 71 60 52
% of total that is oranges & mandarines 84 86 90 88
Europe Total citrus supply tonnes 9,631,873 13,039,703 14,584,512 19,532,380
Total citrus g per capita/day 35 46 55 73
% of total that is oranges & mandarines 77 80 80 81
Agriculture 2013, 3 173
Table 1. Cont.
Region Item 1979 1989 1999 2009
North
America Total citrus supply tonnes 13,292,610 14,506,257 14,141,748 13,928,358
Total citrus g per capita/day 144 143 125 112
% of total that is oranges & mandarines 81 81 82 79
South
America Total citrus supply tonnes 7,516,799 10,525,514 15,148,330 13,530,945
Total citrus g per capita/day 87 99 121 96
% of total that is oranges & mandarines 89 91 83 80
USA production (2011–2012) was 10.6 million tonnes, with 65% from Florida and 32% from
California. However, citrus production in the USA has been declining, apparently because of adverse
climate events such as hurricanes, freezes, and drought [12].
The types of citrus produced and consumed vary throughout the world (Table 1). About 80% of the
citrus grown are oranges and tangerines in most of the world, except for Africa (Table 1). The main
citrus crop produced in the USA is oranges, while Japanese consumers prefer tangerines. Most citrus are
produced in temperate climates, where they grow well. Harvest losses are moderate, at about 50% [6].
In the U.S., current consumption is estimated at 147 g/person/day, which is very high [13]. The total
estimated nutrients contributed by citrus/capita/day in the U.S. in 1970 and 2006 [6] are shown in
Table 2. In 2006, citrus contributed more of the dietary intake of all listed nutrients except fiber, which
was unchanged from 1970. Importantly, citrus provides about 25%–28% of vitamin C/capita/day.
However, citrus actually contributes a lower proportion of dietary carotenoids and folate in 2006 than in
1970. U.S. residents are now consuming more of these nutrients from other sources (e.g., fortified foods
or other fruits and vegetables). Currently, citrus contributes lesser but non-neglible amounts of vitamin
A (mostly derived from beta-cryptoxanthin), folate, fiber and carotenoids (Table 2).
Table 2. Total estimated nutrients contributed by current consumption of citrus and
estimated percentage of total dietary nutrients provided by citrus consumption/capita/day in
the U.S. in 1970 and 2006 [6].
Nutrient 1970 2006
Vitamin C
mg 26.4 32.8
% of dietary nutrients from citrus 24.9 27.6
Vitamin A
µg RAE 3.7 4.3
% of dietary nutrients from citrus 0.3 0.4
Folate (DFE)
µg 19.2 30.5
% of dietary nutrients from citrus 6.4 3.4
Dietary Fiber
g 0.6 0.6
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Table 2. Cont.
Nutrient 1970 2006
% of dietary nutrients from citrus 3.0 2.2
Carotenoids
µg 7.7 8.2
% of dietary nutrients from citrus 1.5 1.2
4. Nutritional and Phytochemical Contents of Citrus
Citrus contains no fat, sodium or cholesterol. The average energy value of citrus is very low which
can be important for consumers concerned about obesity. Citrus contains large amounts of vitamin C and
appreciable amounts of carotenoids (some capable of converting to vitamin A), folate, and fiber. The
amount of selected nutrients are given in Table 3 along with the percentage of the recommended daily
allowance (RDA) or adequate intake (AI) [14] that is met when consuming 100 g of citrus fruit.
Table 3. The amount of nutrients and the percent of the recommended daily allowance or
adequate intake met from the consumption of 100 g of selected citrus fruit [15–18].
Vitamin C Vitamin A* Folate Fiber
Oranges
Children under 9 y (%)
Persons 9+ y
Pregnant/lactating women
53–88 mg
213–589
59–195
44–110
17 µg
3–6
2–4
2–3
30 µg
15–20
8–10
5–6
2.4 g
10–13
6–11
8–9
Grapefruit
Children under 9 y
Persons 9+ y
Pregnant/lactating women
31–61 mg
125–244
35–135
26–76
58 µg
12–15
6–10
4–8
13 µg
7–9
3–4
2–3
1.6 g
6–8
4–8
6
Tangerines
Children under 9 y
Persons 9+ y
Pregnant/lactating women
27–72 mg
107–480
30–160
21–90
46–144 µg
9–36
5–24
4–19
16 µg
8–11
4–5
3–4
1.8 g
7–9
5–9
6
Lemons/limes
Children under 9 y
Persons 9+ y
Pregnant/lactating women
29–61 mg
116–407
32–135
24–76
2–22 µg
0.4–6
0.2–4
0.2–3
11–16 µg
4–7
2–4
1–2
1.8–2.8 g
11–15
9–13
10
* assumes that 12 µg beta-carotene from food forms 1 µg vitamin A, and that 24 µg
beta-cryptoxanthin or alpha-carotene from food forms 1 µg vitamin A; percent of the recommended
intake met by consuming 100 g of food and is based upon the U.S. DRIs [14].
Of course, the nutritional and phytochemical contents of citrus vary widely depending upon growing
conditions, the variety of fruit, maturity, storage conditions, and on processing [5,19,20].
4.1. Vitamin C
Citrus is an excellent source of vitamin C. Most persons can achieve 100% of the RDA for vitamin C
by consuming moderate amounts of citrus fruit (Table 3). Vitamin C (ascorbic acid) is a water-soluble
Agriculture 2013, 3 175
essential nutrient which acts as an antioxidant, is involved in iron metabolism, the biosynthesis of
carnitine, neurotransmitters, collagen and in the cross-linking of these fibers in bone, and is a cofactor in
various enzymatic and hormonal processes [14,21,22]. Vitamin C is also involved in the immune system
by stimulating white blood cell function [23]. Vitamin C can help reduce the risk of pre-eclampsia
during pregnancy [24], and in some studies vitamin C has been shown to lessen the severity and duration
of cold symptoms (reviewed in [23]). In vitro, ascorbic acid was observed to contribute 40%–54% of the
antioxidant potential of oranges, mandarins, and grapefruit [25].
Studies in humans have also provided strong evidence for the antioxidant properties of citrus.
Drinking 500 mL/day of orange juice for two weeks (~250 mg ascorbic acid/day) increased plasma
vitamin C concentrations by 40%–64% and reduced oxidative markers (8-epi-PGF2α) in adults, with a
more pronounced effect in smokers [26]. In another study, a 47% reduction in plasma lipid peroxidation
in healthy adults was observed from the consumption of 8 ounces (~236 mL) of orange juice (~70 mg
vitamin C) every day for two weeks [27]. These data show that rapid improvement of vitamin C and
antioxidant status can be achieved by consuming reasonable amounts of citrus. Vitamin C deficiency is
not typically considered a problem in the U.S. or Canada [14], since U.S. residents consume about
72–102 mg/day of vitamin C from food, or 101–245 mg/day when supplements are included [28].
However, the prevalence of deficiency in the U.S., measured by serum ascorbic acid and indicated by the
NHANES III (1984–1994) and NHANES (2003–2004) data, was ~9%–13% and ~7.1%,
respectively [29]. Smokers, those who abuse drugs and alcohol, and those with diets low in fruits and
vegetables are at higher risk of having low vitamin C [14]. Also, prevalence of mild vitamin C deficiency
worldwide is probably fairly high [9], and data from undernourished women in developing countries
indicates breast milk levels to be inadequate (25 µg/L whereas the AI is 50 µg/L) (taken from [30]).
Regular consumption of citrus can also improve breast milk concentrations. In a study by
Daneel-Otterbech et al. [31], three servings or orange juice (~100 mg vitamin C/serving) for six weeks
doubled milk vitamin C concentrations (1 serving/week had no significant effect). Furthermore, there is
supporting evidence that more than 200 mg/day of vitamin C may be optimal for maximum health
benefits [32], and citrus may be the best food source for increasing vitamin C intake.
4.2. Carotenoids and Vitamin A
Citrus contains many carotenoids. Carotenoids are terpenes (tetraterpenoids) and are yellow and
orange pigments found ubiquitously in plants; over 600 carotenoids have been identified and about 50
are present in the human diet [33,34]. The most abundant carotenoids in the human diet, lutein,
zeaxanthin, lycopene, and the pro-vitamin A carotenoids, α- and β-carotene and β-cryptoxanthin, are
found in fruits and vegetables. Many functions and health benefits of carotenoids have been described:
they are antioxidants, have positive effects on the immune system [33,35–37], promote bone formation
and health [38,39], stimulate gap junction communication between cells [40], promote eye
health [41,42], and lower the risk of cancer [43–45]. Much data support beneficial health effects of
ingesting carotenoids; however, the only well-established health benefit of carotenoids in humans is the
ability of several to form vitamin A [14].
According to NHANES data (2009–2010), most people in the U.S. are not consuming enough
vitamin A from food, and only a small proportion of vitamin A is consumed as carotenoids (~20%–35%
Agriculture 2013, 3 176
of the RDA for vitamin A) [28]. Worldwide, vitamin A deficiency is estimated to affect 209 million
women and children and is the leading cause of preventable blindness [8]. On the other hand, high
intakes of vitamin A from supplements or liver have been associated with negative health effects
including diarrhea, nausea, vomiting, headaches, bone abnormalities and osteoporosis, liver damage,
hair loss, and possibly birth defects [46,47]. Consuming even very large amounts of pro-vitamin A
carotenoids from food is safe [14].
Carotenoids in fruit are dissolved in the chromoplast as opposed to being bound to proteins in the
chloroplasts of dark-leafy green vegetables, and considerable evidence supports fruit carotenoids having
higher bioavailability [48,49]. Tangerines in particular can provide a substantial amount of the
pro-vitamin A carotenoid, β-cryptoxanthin, a carotenoid that appears to be a highly bioavailable source
of vitamin A [50,51]. In a recent study of breastfeeding women with low vitamin A status, the
consumption of tangerines (254 g or ~ 5.3 g/day β-cryptoxanthin) for 18 days maintained vitamin A
concentrations in breast milk and increased plasma and milk β-cryptoxanthin [52]. These results suggest
that the vitamin A contributed by tangerines might be more than twice as much than assumed, such that
100 g of tangerine would meet as much as 72% of the recommended daily intake of vitamin A for
children. Furthermore, estimates of production and consumption of tangerines specifically demonstrate
the capacity to provide significant amounts of vitamin A to populations experiencing vitamin A
deficiency if β-cryptoxanthin-rich varieties are selected for production and consumption [53].
4.3. Folate
As a coenzyme, folate participates in converting deoxyuridylic acid to thymidylic acid, in the
production of purines (formation of glycinamide ribonucleotide and 5-amino-4-imidazole carboxamide
ribonucleotide), and the interconversion of many amino acids; thus, folate is necessary for DNA
production, is involved in homocysteine regulation, and protein production primarily via methylation
transfer reactions [14]. Because DNA production is high during pregnancy, lack of folate is associated
with birth defects such as neural tube defects [54]. Lack of folate is also implicated in higher
homocysteine concentrations, which increase the risk of atherosclerosis and heart disease [14]. Citrus
can be a complementary source of dietary folate and can provide up to 10% to 20% of the RDA for adults
and children less than 9 years of age, respectively, with just 100 g. A study on commercial orange juices
in Europe found that the folate was 100% bioavailable and highly stable [55], and, in another study, the
consumption of orange juice (750 mL) daily for four weeks increased plasma folate concentrations in
adults by 18% [56].
4.4. Fiber
Dietary fiber is the edible carbohydrate and lignin in plants that is not digested and absorbed in the
small intestine; fibers can promote laxation, satiety, reduce the uptake and/ or reabsorption of glucose,
fat, cholesterol, and bile acids thus reducing cardiovascular disease risk and possibly decreasing food
intake and promoting healthy intestinal fermentation [57,58]. The main fiber in citrus is pectin, a soluble
fiber, which makes up 65%–70% of the total fiber content [59]. Pectin is more completely fermented in
the gut by microflora than foods rich in cellulose like cereals and fermentation produces various
substrates including short-chain fatty acids that can be absorbed and provide energy [14,58]. There is
Agriculture 2013, 3 177
conflicting data on whether fiber may interfere with the absorption of other nutrients; however, most
studies on pectin/ nutrition interactions did not show a decrease in nutrient bioavailability except when
large doses of pectin (12 g and 0.15 g/kg body weight) were concomitantly consumed [60,61]. Thus, it
has been concluded that a diet rich in dietary fiber will not cause adverse effects in healthy people [14].
The average U.S. adult consumes only ~57% of the RDA for fiber [28]. Because the RDA for fiber is
not being met by many adults and dietary fiber can reduce the risk of chronic diseases, citrus can make a
valuable contribution to meeting daily fiber goals. Lowering of cholesterol in particular by citrus,
however, may depend upon the amount, degree of esterification, molecular weight, and viscosity of the
fiber/pectin consumed [58,62] but may be significant with dietary intake that is achievable (2.2–9 g
pectin for 30 days) (in[57]).
4.5. Flavonoids and Limonoids
Flavonoids are polyphenolic compounds widely distributed in plants and are pigments responsible for
fruit and flower coloration [63] and involved in defense against UV radiation or aggression from
pathogens [64]. Flavonoids are divided into multiple classes of compounds such as flavones, flavanones,
isoflavones, flavonols, flavanols, flavan-3-ols (tannins, catechins), anthocyanidins, aurones, chalcones,
and coumarins [65–67]. Citrus is the major source of flavanones from food [65]; the most predominant
and widely studied flavanones in citrus are hesperetin (aka hesperidin) (predominant in oranges) and
naringenin (predominant in grapefruit) [63,67,68]. Of the edible parts, the membranous segments of
citrus fruit have the highest content of many bioactive compounds making high-pulp juices more
recommended for consumption [5]. Although the peels and seeds are often discarded, they generally
have different flavonoid composition than the edible fruit [63] making citrus byproducts a good source
of flavonoid extracts. Furthermore, the peels and seeds can contain the highest amounts of flavonoids;
for example the albedo (pith) of an orange can have up to five times higher flavanone content than
orange juice [64].
The health benefits of citrus flavonoids have been generally studied using individual extracted
compounds instead of whole foods, but these studies have had promising results. Flavonoids extracted
from citrus have been shown to act as antioxidants and anti-inflammatory agents, to reduce cholesterol
and triglycerides [69,70], and improve bone health [70,71] in experimental animals.
Their effects in humans are more controversial, because there is large intra- and inter-variability in
absorption, metabolism, and reported effects of flavonoids. Furthermore, the solubility of flavonoids is
often low and effected by microbiota in the gut [67,72,73]. Thus, the amount of flavanones from whole
citrus fruits may be very different than those that have beneficial effects in studies of animal models
using extracts. Nevertheless, in a study in adults with metabolic syndrome, the consumption of 500 mg
hesperitin/day as a supplement for three weeks resulted in improved brachial artery flow-mediated
dilation and reduced markers of inflammation (C-reactive protein, serum amyloid A protein, soluble
E-selectin) [74]; for comparison 236 mL (~ 8 oz) of orange juice contains ~39–62 mg of hesperitin [66].
Observational data indicate that dietary intake of flavanones (primarily hesperitin) is estimated at 15.4 to
69.54 mg/day in people from European countries (EPIC study) [75] and 17 to 24 mg flavonoids/day in
people from Finland [76], the UK [77], and the U.S. [78]. Higher intakes of flavonoids found in citrus
were associated with lower cardiovascular disease risk, asthma [76], and higher bone mineral
Agriculture 2013, 3 178
density [77]. Although observational evidence may be correlating health benefits to increased fruit and
vegetable intake rather than specifically to flavonoid intake, the data from cell culture, animal studies,
and limited human studies that associate citrus flavanones to positive health outcomes is encouraging.
The bitter taste in citrus can be attributed to limonoids. Limonoids are terpenes and occur only in
plants of the Rutaceae (citrus) and Meliaceae (neem, mahogany) families [79]. The most abundant
limonoids in citrus are glycosides of limonin and nomilin [79,80]. Citrus can contain 150–300 mg of
limonoids in 100 g of fruit whereas the peels and flesh solids can contain 500 mg per 100 g fruit. In
animal and human cell lines, limonoids have been shown to help reduce or inhibit proliferation of cancer
of the pancreas, stomach, colon, and breast; in animal studies, limonoids also reduced skin
tumors [81–83]. There is evidence of antiviral and antibacterial, properties of limonoids [84–86]. Most
studies on limonoids have used extracted compounds rather than citrus as a whole food making
translation of the dose used in cell culture and animal studies to intake in humans difficult; however,
with high concentrations of limonoids in citrus, it may be highly participatory in providing the health
benefits described.
5. Evidence of Health Benefits of Whole Citrus Fruits
The data on individual compounds contained in citrus shows that these can be related to antioxidant
activity and health outcomes such as diabetes [87,88]. However, much of the data can be difficult to
place in context of whole foods. Although many of the nutrients and phytochemicals found in citrus may
exert positive health outcomes, the combination of these compounds in a whole fruit may have
synergistic or antagonistic effects. Evidence is building that citrus fruits as whole foods, not just
extracted individual compounds, may provide a plethora of health benefits. In an in vitro comparison
study of common fruit, lemons exerted very high antioxidant and antiproliferative activities; lemons and
grapefruit also decreased proliferation of human liver cancer cells in a dose-dependent manner [89]. In
humans, the antioxidant effects of orange juice have been observed with as little as 8 ounces (236 mL)
consumed for two weeks [27]. Even in the presence of a high-fat diet or high-fat/ carbohydrate meal,
orange juice (containing either 500 mg of vitamin C or 300 kcal (probably ~630 mL) reduced the acute
effects of oxidative and inflammatory stress [90,91].
Evidence for improved cardiovascular health biomarkers and insulin sensitivity have also been
observed in some but not all studies consuming citrus. In obese children, consumption of mandarin juice
(500 mL/day for 1 month) reduced biomarkers of oxidative stress, increased antioxidants (vitamin E, C,
and glutathione), reduced blood pressure, and lowered insulin or improved insulin resistance
homoeostasis [92]. In hypercholesterolemic adults, 750 mL, but not 250 or 500 mL, of orange juice daily
for four weeks increased HDL and decreased LDL/HDL ratios as well as increased plasma folate and
vitamin C concentrations [56]. However, mildly hypercholesterolemic adults consuming a moderate
volume of orange juice (480 mL/day for 10 weeks), did not have an improvement in plasma lipid profiles
unless the orange juice was fortified with plant sterols (2 g/day) [93]. Also in a small study of healthy
adults where 236 mL of orange juice was incorporated into habitual diets three times a day for three
weeks, cholesterol concentrations were unaffected [94].
Fat and weight gain was inhibited by feeding mice blood orange juice (ad libitum in place of water)
for three months with a high-fat diet, and enhanced insulin sensitivity, decreased serum triglycerides,
Agriculture 2013, 3 179
total cholesterol, alanine aminotransferase, and reduced liver steatogenisis were observed [95,96].
Evidence of an anitobesity effect of citrus in humans, however, is lacking.
Thus, the evidence for health benefits of whole citrus fruits is sparse, but promising. In summary, the
amount of citrus needed to provide health benefits is quite variable but appears to be within reasonably
consumable amounts. One to three glasses of orange juice a day appears to provide improvement in
antioxidant, cardiovascular, and insulin sensitivity biomarkers as well as increase vitamin C
concentrations in plasma and breast milk. Two large tangerines a day may provide a substantial amount
of carotenoids and improve vitamin A concentrations. Contributions to folate, fiber, and phytochemicals
in the diet from citrus could also be beneficial, but the amount needed to obtain the health benefits
observed in studies is uncertain. Extracted compounds from citrus from peels and seeds that are
generally discarded, such as pectin, flavonoids, and limonoids, may also be beneficial to health, but the
amounts needed to have an effect are also uncertain.
Many nutrients and phytochemicals are degraded when exposed to light, oxygen, and during
extracting procedures [33,97,98]. Thus, whole citrus consumption may provide increased nutritional
benefits compared to supplements and sometimes even juices. For example, oranges often contain
higher amounts of carotenoids and fiber than orange juice [15]. On the other hand, many compounds
such as folate may have limited bioavailability from food [14] or, as in flavonoids, are not present in
concentrations in food as high as those used in studies suggesting a health benefit (see section 4.5). Thus,
depending on the compound, juices, extracts, or supplements may be a more abundant or bioavailable
source of the phytonutrient than whole foods [88]. However, while specific nutritional inadequacies may
require the consumption of supplements in certain groups, it is generally recommended that most
nutrients be obtained primarily from whole foods rather than from supplements [99]. Overall, the
compounds in citrus, whether obtained from whole foods, extracts, or supplements, appear to have
positive health benefits.
6. Barriers of Increasing Citrus Intake and Recommendations
In some areas, such as the U.S., production and consumption of citrus fruit (per capita/day) has
declined. In addition, the production of processed citrus in the U.S. (7.3–7.7 million tonnes in 2012 and
10.5–12.7 million tonnes in 1999) [100,101] and its consumption in top markets (U.S., European Union)
has declined [102]. Lower production can be attributed to citrus diseases and fewer new plantings due to
low prices in the past, and lower consumption because of greater competition from other fruits now
available due to improved logistics in transportation and in packaging [1,103]. Although consumption
data should be interpreted with caution because it is restricted to the availability of data and is a
reflection of availability of food for consumption rather than actual intake, as with most commodities,
price and accessibility heavily influence citrus consumption. The price of citrus at the consumer level is
multifaceted and influenced heavily on complex trade matrices, thus there have been calls for reforms in
the citrus industry for promotion of long-term relationships along the supply lines to consumers allowing
the “share of risk of price and yield variability and costs of marketing promotion, and on-going
R&D” [1]. Increasing domestic production, improving current yields, and investing in transportation,
storage, and production infrastructure, especially in developing countries, may improve accessibility,
which can influence price. Agriculturalists, governments, and industry can provide assistance in
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increasing production and trade and provide information to improve citrus varieties. For example, some
nutrients and phytochemicals can be increased by not only selecting for nutrient-rich varieties of citrus,
but also by manipulating external conditions and harvesting times. Vitamin C can be increased by
increasing potassium and maintaining adequate zinc, magnesium, and copper in the soil, and can be
negatively affected by elevated nitrogen from fertilizer; growth and storage in cooler temperatures, and
growth in direct sunlight can also increase and retain vitamin C in citrus as well as the type of rootstock
the citrus is grafted on [18].
Another barrier is a dearth of knowledge about the nutrient content, bioavailability, and potential
health benefits of citrus varieties grown in tropical areas. Currently most research and development has
been done using common citrus fruits grown in temperate climates, such as oranges, lemons, and
mandarins. Encouraging research on lesser known citrus varieties, and developing citrus varieties
capable of expanding into new environs might increase consumption in low income countries that
currently lack sufficient domestic citrus production and extend the potential health benefits of citrus to
these populations. Finally, promoting the nutritional and health benefits of citrus may correspondingly
encourage consumption.
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... Several epidemiological studies have revealed that vitamin C scavenges the free radicals or reactive oxygen species in our body, thereby protecting cells, DNA, and lipids from oxidative damage. Vitamin C content in grapes is between 31 and 61 mg/100 g (Turner & Burri, 2013). ...
... Vitamin C Antioxidant, ROS scavenger 31-61 mg/100 g f.w. Whole Turner & Burri, 2013 Total phenolics Immunomodulatory properties, scavenging of free radicals, inhibition of lipid oxidation, reduction of hyperoxide formation 250 mg GAE/100 g f. w. Whole Percival, 2009;Kakuda et al., 2000 Anthocyanins Immunomodulatory, antioxidant, anti-inflammation, anticancer, antiaging, cardioprotective, and antimicrobial properties 55 mg/100 g f.w. ...
... They stimulate the generation of white blood cells and inhibit DNA oxidation (Wintergerst et al., 2007). Vitamin C concentration in oranges ranged between 53 and 88 mg/100 g (Etebu & Nwauzoma, 2014;Turner & Burri, 2013). Although vitamin C is a major contributor to the antioxidant capacity of oranges, other nonnutritive components like carotenoids and flavonoids also contribute to the total antioxidant potential of the fruit. ...
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Our immune system depends on leucocytes or white blood cells which possess the power to produce antibodies to fight various disease‐causing pathogens. People have now realized the crucial role played by the immune system in keeping them healthy. Therefore, recent scenario has witnessed an upsurge in the demand of immunity boosting foods. The use of naturally available fruits as immunomodulators is so ubiquitous and just needs concrete scientific proofs for claiming its efficacy. Many studies have shown that fruits are abundant in bioactive compounds like vitamins (vitamin A, C, E, etc.), minerals, and phytochemicals (like β‐ carotene, flavonoids, tannins, and phenolics, etc.). These components have the potential to enhance our immunity by supporting the proliferation of lymphocytes, scavenging free radical species, reducing oxidative stress, improving anti‐inflammatory as well as immunomodulatory mechanism, and supporting aggregation of platelets. Thus, supplementation of diet with an appropriate amount of fruits daily could support body's natural defense by strengthening our immune response. In this preface, we attempt to summarize the significant role played by various phytochemicals and bioactive compounds of fruits in boosting our immune system.
... Citrus is a valuable source of vitamin C. By consuming a moderate amount of citrus fruits each day, an individual can achieve 100 percent Vitamin C level. Vitamin C is an essential water-soluble vitamin essential for the body's defense [22]. It is transmitted through muscle fibers, carnitine biosynthesis, neurotransmitters, collagen, and bones because these particles connect the fibers. ...
... The highest carotenoid levels, such as lutein, zeaxanthin, lycopene, and vitamin A, are found in fruits and vegetables, including orange and carotene. Benefits of carotenoids in foods include improving immune function, promoting bone formation, promoting eye health, and maintaining visual quality [22]. There is a large amount of data supporting that carotenoids reduce the risk of cancer, macular degeneration, cataracts, skin damage to the sun, and cardiovascular diseases [29]. ...
... The most notable folate compounds in Citrus are the reduced 5-methyl tetrahydrofolate (monoglutamate) and polyglutamate compounds [34]. Folate plays a vital role in DNA, which is involved in homocysteine regulation and protein production primarily through the methylation transfer reactions [22]. Because there is a high DNA production during pregnancy, a folate deficiency is significantly linked to birth defects such as neural tube defects [35]. ...
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Citrus fruits are essential sources of food and energy and play a critical role in supplementing healthy diets. Citrus fruits contain mostly carbohydrates such as sucrose, glucose, and fructose and are good dietary fiber sources, which help prevent gastrointestinal disease and promote high circulating cholesterol. Besides, citrus fruits are also significant sources of vitamin C and various bioactive compounds. It is suggested that these components are of vital importance in improving human health due to their antioxidant properties and being converted to vitamin A. However, citrus fruit is still being used for different purposes like juice, jam, jelly, squash, pies, cake, candies, marmalades, etc. Most citrus waste materials are currently used as animal feed. Innovations are occurring in the conversion of citrus by-products into valuable commodities with the development of innovative technologies. This chapter has put up primary and secondary research findings of citrus fruits, especially lemon and pomelo, their chemical properties, composition, and their use in health and cosmetic needs.
... The citrus species, belonging to the family Rutaceae, are the most popular agricultural product in the world (Turner and Burri, 2013). Turkey is one of the main citrus producers among the World countries and ranks 9 th in the World (Faostat, 2016). ...
... Global shift to healthy eating is evident in all standard family and individual meals in households. Fruits contribute quantifiable amounts of nutrients, antioxidants, and minerals which are essential for healthy living (Bergh 1992;Maldonado-Celis et al. 2019;Turner and Burri 2013). The change in consumerism and the accompanying demand continue to open up avenues and expansion of fruit production in SSA but unfortunately current and future demand is unlikely to be met considering limitations imposed by various biotic and abiotic factors. ...
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Fruit production in Sub-Saharan Africa is of paramount importance both socially and economically. Millions of farmers derive livelihoods from mango, avocado, citrus, cashew, and coconut farming, but native and alien invasive species constrain production The region’s capacity to contain invasives is weak due to the absence of national and institutional support systems for early detection, containment, eradication, or management of the pests. Climate change is expected to play a huge role in the influx of more alien invasive species and the shift of ecological requirements of some native species. Though a fair share of pre-and post-management pest management techniques for several insect pests has been developed, adoption and adaptation of the options are limited. Data on economic and social implications are largely lacking, making it challenging to implement informed policy decisions. The existence of the “Strategy for Managing Invasive Species in Africa 2021–2030” promises a paradigm shift in the management of invasives, from reactive thinking to coordinated proactive approaches. The uncoordinated deployment of management measures in the region and the lack of funding, play a negative role in managing the pests effectively. Prospects for enhanced future research are wide, and efforts are currently being channeled to Area-Wide-Integrated Pest Management in a bottom-up approach with stakeholders owning the process. Participatory development of technologies is also taking centre stage, paving the way for increased adoption and adaptation. Postharvest technologies promise to provide the adequate phytosanitary assurance required by countries importing fruit from Sub-Saharan Africa.
... Apples and citrus fruits are extensively consumed in many countries, and they are considered to be valuable health-promoting food as they contain biologically active components such as ascorbic acid, carotene (provitamin A) and group B vitamins, flavonoids, carotenoids, and phenolic acids, which have beneficial effects for human health [1][2][3][4]. Systematic consumption of fruits and vegetables reduces the risk of civilisation diseases and also facilitates body mass control [5][6][7][8]. Reports of the World Health Organisation of the Food and Agriculture Organisation recommend that adults should consume at least five portions of fruits and vegetables daily [9,10]. ...
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Over the span of the last decade, certain pesticides have been banned in apple tree and citrus tree cultivations. Hence, it is important to conduct research focused on estimating the occurrence of residues of pesticides from the perspective of compliance with the relevant legislative regulations. Equally important is to estimate the reduction in pesticide residues through simple procedures such as washing and peeling. This research was conducted in the years 2012 and 2020. An assessment was made of the effect of in-house processing, such as conventional washing with tap water and peeling, on the level of pesticide residues in apples and citrus fruits (oranges, grapefruits and lemons). The level of pesticide residue was determined with the use of the QuEChERS method of extraction in conjunction with LC-MS/MS analysis. One can clearly observe a smaller number of pesticides identified in the edible parts of fruits in 2020 (seven pesticides in apples and three in citrus fruits) compared to 2012 (26 pesticides in apples and 4 in citrus fruits). In apples from 2012, only in the case of disulfoton was the maximum residue limit (MRL) exceeded, while in samples of apples from 2020 no instance of exceeded MRL was noted. This study did not reveal exceeded MRL values in the edible parts of citrus fruits in the analysed years. The absence of detected instances of pesticides not approved for use in the analysed years indicates that the producers complied with the relevant legislative regulations. The results obtained indicate that conventional washing with water (about 1.5 L/one fruit) did not have any effect on the level of pesticide residues in the analysed fruits. Apple peeling allowed for a reduction in pesticide levels in the range of 24% (carbendazim) to 100% (triflumuron, thiodicarb, tebuconazole).
... Citrus is the largest genus in the family Rutaceae and it is one of the most traded horticultural products in the world (Turner and Burri, 2013). Citrus fruits are native to the tropical and subtropical areas of Asia and later they spread to other parts of the world (Liu et al., 2012). ...
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Purpose: The availability of fresh Citrus fruits is limited by their susceptibility to invasion by microbial pathogens which leads to cause serious postharvest losses. The present study was carried out to isolate and morphologically identify postharvest fungal associations from selected Citrus fruit species (C. sinensis, C. limon, C. crenatifolia and C. medica) and to confirm their identity by molecular characterization. Research Method: Postharvest fungal associations of selected Citrus fruit species were isolated, and identification was done based on morphological characteristics. Confirmation of fungal associations was done through phylogenetic analysis of newly generated ITS sequencing data. Further, frequency of occurrence of each fungal isolate was calculated in three different districts in Sri Lanka. Findings: From the morphological and molecular identification, Collectrichum fructicola, Collectrichum gloeosporioides, Lasiodiplodia theobromae, Aspergillus niger and Pestalotiopsis sp. were recorded from C. sinensis. Neofusicoccum parvum, Collectrichum gigasporium and Aspergillus clavatus were isolated from C. crenatifolia. Further, Lasiodiplodia theobromae and L. pseudotheobromae were the only fungal association isolated from C. limon and C. medica fruit species, respectively. It is worthwhile noting that this is the first report of association of the C. gigasporium and Pestalotiopsis sp. from Citrus fruits in Sri Lanka. Research Limitations: Since this research was mainly focused on the isolation and identification of the potential fungal associations, pathogenicity evaluation could not be carried out. Originality/value: Findings of potential disease causative agents in citrus will be valuable for agriculture sector, to adopt and practice effective strategies to minimize postharvest losses of citrus fruits.
... Citrus fruits are economically significant in Egypt, with their large-scale production, estimated at 4.5 million tons per year, playing an important role in the region's fruit economy. Citrus fruits have a variety of positive health and nutrient properties [4], due to their richly in vitamin C and folic acid, and they are free of sugar, sodium, and cholesterol. Citrus fruits' potassium, calcium, folate, thiamine, niacin, vitamin B6, phosphate, magnesium, and copper levels may lower the risk of heart disease, various types of cancer, and respiratory system diseases, reducing the risk impacts of coronavirus pandemics like COVID-19 on humans [5][6][7]. ...
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Iron (Fe) is required for most metabolic processes, including DNA synthesis, respiration, photosynthesis, and chlorophyll biosynthesis; however, Fe deficiency is common in arid regions, necessitating additional research to determine the most efficient form of absorbance. Nano-fertilizers have characteristics that are not found in their traditional equivalents. This research was implemented on Washington navel orange trees (Citrus sinensis L. Osbeck) to investigate the effect of three iron forms—nano (Fe-NPs), sulfate (FeSO4), and chelated (Fe-chelated)—as a foliar spray on the growth, fruiting aspects, and nutritional status of these trees compared to control. The highest values of the tested parameters were reported when the highest Fe-NPs level and the highest Fe-chelated (EDTA) rate were used. Results obtained here showed that the spraying of the Washington navel orange trees grown under similar environmental conditions and horticulture practices adopted in the current experiment with Fe-NPs (nanoform) and/or Fe-chelated (EDTA) at 0.1% is a beneficial application for enhancing vegetative growth, flower set, tree nutritional status, and fruit production and quality. Application of Fe-NPs and Fe-chelated (EDTA, 0.1%) increased yield by 32.0% and 25% and total soluble solids (TSS) by 18.5% and 17.0%, respectively, compared with control. Spraying Washington navel orange trees with nano and chelated iron could be considered a significant way to improve vegetative growth, fruit production, quality, and nutritional status while also being environmentally preferred in the arid regions.
Article
When assessing citrus fruit quality, besides natural health-promoting compounds, attention also has to be paid to residues of chemicals used to protect fruit against various pests. A set of 49 samples of different types of citrus fruits collected at the Czech market were analysed for 460 pesticide residues using LC-MS/MS and GC-MS/MS methods. While no residues were detected in citruses from organic farming, altogether 38 various pesticide residues were detected in conventional production samples. Buprofezin in two grapefruit samples and fenbutatin oxide in one tangerine sample exceeded maximum residue limits (MRLs). Depending on the pesticide group, 10–70% of residues were found in pulp, this means that their processing factors calculated for peeling are in the range of 0.02–0.76. In the case of a beverage prepared from unpeeled lemon slices, the transfer of residues from contaminated fruit into infusion was, depending on the beverage type and processing conditions, in the range of 8–61%.
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A number of Agro-industrial by-products or wastes like citrus pulp, citrus meals, citrus seed meal, citrus molasses, and citrus peels are generated from fresh citrus after the main products of interest have been removed or extracted during processing or peeled for direct human consumption as in the case of developing countries. The waste utilization of orange peel is the most important aspect of this study. The Present Study was undertaken to prepare orange peel pickle by using different preservatives and to assess its shelf life and overall acceptability of pickle in sensory evaluation. The study was conducted to note down the efficacy of preservatives on the shelf life of pickles. Sensory evaluation was done in order to see the acceptability of the product for parameters color, flavor, aroma, texture, and overall appearance. In the first treatment, the pickle was prepared with sugar. In the second treatment, pickle was prepared with jaggery. Both combinations were observed majorly for taste and shelf life. Treatment 1 (T1) showed the best result in terms of shelf life and Treatment 2 (T2) showed the best result in terms of sensory.
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Recent studies have documented a number of health benefits associated with the consumption of citrus. These fruits are predominantly composed of water and have a very low energy density. However, they are some of the most important nutrient-dense foods available. In effect, citrus fruits contain a range of key nutrients such as vitamin C, folate, dietary fiber, minerals (potassium) and phytochemicals, which confer them the health-promoting properties. In recent years, there has been increasing interest in the anti-oxidant capacity of foods. Vitamin C is a major contributor to the anti-oxidant capacity of citrus. However, the major contribution of citrus anti-oxidant activity comes from the combination of phytochemicals and from their synergistic action with vitamin C. The major phytochemicals in citrus fruits are the terpenes and phenolic compounds, which possess anti-inflammatory and anti-carcinogenic activity. Carotenoids and limonoids are terpenes that are released in the processing of juices. Citrus is the main source of specific nutrients such as flavanones (hesperetin and naringenin, usually present as glycosides) and the carotenoid cryptoxanthin, which are not present in other fruits in significant quantities. Flavonoids also have a role in cardiovascular protection, inhibiting the formation of atheroma in many steps of its pathogenesis.
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For some classes of dietary polyphenols, there are now sufficient intervention studies to indicate the type and magnitude of effects among humans in vivo, on the basis of short-term changes in biomarkers. Isoflavones (genistein and daidzein, found in soy) have significant effects on bone health among postmenopausal women, together with some weak hormonal effects. Monomeric catechins (found at especially high concentrations in tea) have effects on plasma antioxidant biomarkers and energy metabolism. Procyanidins (oligomeric catechins found at high concentrations in red wine, grapes, cocoa, cranberries, apples, and some supplements such as Pycnogenol) have pronounced effects on the vascular system, including but not limited to plasma antioxidant activity. Quercetin (the main representative of the flavonol class, found at high concentrations in onions, apples, red wine, broccoli, tea, and Ginkgo biloba) influences some carcinogenesis markers and has small effects on plasma antioxidant biomarkers in vivo, although some studies failed to find this effect. Compared with the effects of polyphenols in vitro, the effects in vivo, although significant, are more limited. The reasons for this are 1) lack of validated in vivo biomarkers, especially in the area of carcinogenesis; 2) lack of long-term studies; and 3) lack of understanding or consideration of bioavailability in the in vitro studies, which are subsequently used for the design of in vivo experiments. It is time to rethink the design of in vitro and in vivo studies, so that these issues are carefully considered. The length of human intervention studies should be increased, to more closely reflect the long-term dietary consumption of polyphenols.
Conference Paper
Based on animal studies, epidemiologic studies and intervention trials, maternal folic acid is known to be protective for neural tube defects (NTD), primarily spina bifida and anencephalus. To reduce the risk of NTD, the U.S. Food and Drug Administration mandated that all enriched cereal grain products be fortified with folic acid as of January 1998. Recent data demonstrate that this public health action is associated with increased folate blood levels among U.S. women of childbearing age and that the national rate of spina bifida has decreased by 20%. Rates of anencephaly appear not to have declined. Epidemiologic data on use of folate and folate antagonists have also implicated folic acid in prevention of other birth defects such as facial clefts and cardiac and limb defects. Dietary folic acid is likely to be inadequate for maximal protection against NTD. Because about half of pregnancies in the U.S. are unplanned, according to the March of Dimes, birth defect prevention includes a recommended daily dose of 400 A,g synthetic folic acid for women of childbearing age. Uniform compliance is estimated to decrease the incidence of NTD by up to 70%. This could reduce the overall incidence from 2 to 0.6 per 1000 pregnancies and prevent disease in similar to2000 babies per year in the U.S. Four thousand micrograms of folic acid per day is recommended for women with previous pregnancies affected by NTD.
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Polyphenols are abundant micronutrients in our diet, and evidence for their role in the prevention of degenerative diseases is emerging. Bioavailability differs greatly from one polyphenol to another, so that the most abundant polyphenols in our diet are not necessarily those leading to the highest concentrations of active metabolites in target tissues. Mean values for the maximal plasma concentration, the time to reach the maximal plasma concentration, the area under the plasma concentration-time curve, the elimination half-life, and the relative urinary excretion were calculated for 18 major polyphenols. We used data from 97 studies that investigated the kinetics and extent of polyphenol absorption among adults, after ingestion of a single dose of polyphenol provided as pure compound, plant extract, or whole food/beverage. The metabolites present in blood, resulting from digestive and hepatic activity, usually differ from the native compounds. The nature of the known metabolites is described when data are available. The plasma concentrations of total metabolites ranged from 0 to 4 mumol/L with an intake of 50 mg aglycone equivalents, and the relative urinary excretion ranged from 0.3% to 43% of the ingested dose, depending on the polyphenol. Gallic acid and isoflavones are the most well-absorbed polyphenols, followed by catechins, flavanones, and quercetin glucosides, but with different kinetics. The least well-absorbed polyphenols are the proanthocyanidins, the galloylated tea catechins, and the anthocyanins. Data are still too limited for assessment of hydroxycinnamic acids and other polyphenols. These data may be useful for the design and interpretation of intervention studies investigating the health effects of polyphenols.
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Citrus limonoids are one of the two main types of compounds responsible for the bitter taste in citrus fruits. Nomilin and limonin are two most predominant limonoids found in Rutaceous plants such as lemon, lime, orange, and grapefruit. Recently, it has been discovered that citrus limonoids possess certain biological activities that may be useful as chemopreventive agents. This article probes the possible role of citrus limonoids in the inhibition of forestomach tumors, lung tumors and skin carcinogenesis.