Article

Iron absorption from brown rice/brown rice-based meal and milled rice/milled rice-based meal

Abstract

Milled rice is the staple food among Filipinos and is mostly consumed three times a day. Rice as a source of iron could therefore have an important role in the existing 37% prevalence of iron-deficiency anemia in the country. Previous iron absorption studies in Filipinos from rice and rice-based meals were carried out on milled rice but no research was done on brown rice of the same variety. This leads to the hypothesis that brown rice may be better than milled rice in terms of iron content. To determine iron absorption from brown rice and brown rice-based meal, and from milled rice and milled rice-based meal of the same variety. The rice variety used in the study was F(2) seeds of PSB Rc72H. Iron absorption from brown/milled rice and brown/milled rice-based meals was determined in 12 healthy human subjects from the incorporation of radioisotopes of iron into erythrocytes 14 days after administration of the labeled rice/rice-based meals. The above samples were also analyzed for nutrient content, including dietary fiber, and iron. The iron content of brown rice was significantly higher (1.1 +/- 0.1 mg/100 g) than that of milled rice (0.6 +/- 0.1 mg/100 g). Brown rice has significantly greater amounts of total dietary fiber (5.4 +/- 0.4%) than milled rice (1.7 +/- 0.2%; P < 0.05). Both tannic acid and phytic acid contents in brown rice (56.9 +/- 3.2 mg/100 g and 290.1 +/- 18.0 mg/100 g, respectively) were significantly higher than those of milled rice (21.3 +/- 2.3 mg/100 g and 84.0 +/- 12.4 mg/100 g, respectively; P<0.05). The amount of iron absorbed from brown rice (0.13 +/- 0.02 mg) did not differ significantly from that from milled rice (0.14 +/- 0.02 mg). However, the amount from brown rice-based meal (0.36 +/- 0.04 mg) differed significantly from that from brown rice (P<0.05) as well as that from milled rice-based meal (0.35 +/- 0.03 mg) from that from milled rice (P<0.05). Moreover, brown rice-based meal did not differ significantly from milled rice-based meal (P<0.05). Iron absorbed from milled rice and brown rice did not differ significantly, as well as that from brown rice-based meal and milled rice-based meal. Differences in iron absorbed from brown/milled rice and brown/milled rice-based meals may be due to the iron content of the test foods and the presence of iron enhancers in the meal (e.g. fish, vegetables and citrus fruit).
International Journal of Food Sciences and Nutrition,
December 2009 60(8): 688693
Iron absorption from brown rice/brown rice-based
meal and milled rice/milled rice-based meal
TRINIDAD P. TRINIDAD
1
, AIDA C. MALLILLIN
1
,
ROSARIO S. SAGUM
1
, DAVE P. BRIONES
1
,
ROSARIO R. ENCABO
1
& BIENVENIDO O. JULIANO
2
1
Food and Nutrition Research Institute, Department of Science and Technology, Bicutan, Taguig,
Metro Manila, Philippines, and
2
Philippine Rice Research Institute Los Baños, College, Laguna,
Philippines
Abstract
Background Milled rice is the staple food among Filipinos and is mostly consumed three times
a day. Rice as a source of iron could therefore have an important role in the existing 37%
prevalence of iron-deciency anemia in the country. Previous iron absorption studies in Filipinos
from rice and rice-based meals were carried out on milled rice but no research was done on
brown rice of the same variety. This leads to the hypothesis that brown rice may be better than
milled rice in terms of iron content.
Objective To determine iron absorption from brown rice and brown rice-based meal, and from
milled rice and milled rice-based meal of the same variety.
Methods The rice variety used in the study was F
2
seeds of PSB Rc72H. Iron absorption from
brown/milled rice and brown/milled rice-based meals was determined in 12 healthy human
subjects from the incorporation of radioisotopes of iron into erythrocytes 14 days after admin-
istration of the labeled rice/rice-based meals. The above samples were also analyzed for nutrient
content, including dietary ber, and iron.
Results The iron content of brown rice was signicantly higher (1.1 ±0.1 mg/100 g) than that
of milled rice (0.6 ±0.1 mg/100 g). Brown rice has signicantly greater amounts of total dietary
ber (5.4 ±0.4%) than milled rice (1.7 ±0.2%; P<0.05). Both tannic acid and phytic acid
contents in brown rice (56.9 ±3.2 mg/100 g and 290.1 ±18.0 mg/100 g, respectively) were
signicantly higher than those of milled rice (21.3 ±2.3 mg/100 g and 84.0 ±12.4 mg/100 g,
respectively; P<0.05). The amount of iron absorbed from brown rice (0.13 ±0.02 mg) did not
differ signicantly from that from milled rice (0.14 ±0.02 mg). However, the amount from
brown rice-based meal (0.36 ±0.04 mg) differed signicantly from that from brown rice
(P<0.05) as well as that from milled rice-based meal (0.35 ±0.03 mg) from that from milled
rice (P<0.05). Moreover, brown rice-based meal did not differ signicantly from milled rice-
based meal (P<0.05).
Conclusion Iron absorbed from milled rice and brown rice did not differ signicantly, as well as
that from brown rice-based meal and milled rice-based meal. Differences in iron absorbed from
brown/milled rice and brown/milled rice-based meals may be due to the iron content of the test
foods and the presence of iron enhancers in the meal (e.g. sh, vegetables and citrus fruit).
Keywords: Iron absorption, brown rice, milled rice
Correspondence: Trinidad P. Trinidad, PhD, Scientist II, FNRI, DOST General Santos Avenue, Bicutan, Taguig, Metro
Manila 1631, Philippines. Tel: 632 837 2071, loc. 2281. Fax: 632 837 2934. E-mail: tptrinidad@yahoo.com
ISSN 0963-7486 print/ISSN 1465-3478 online 2009 Informa UK Ltd
DOI: 10.3109/09637480701830404
Downloaded By: [World Health Organization (HINARI)] At: 13:13 16 December 2009
Introduction
Iron-deciency anemia is prevalent in most developing countries, like the Philippines.
According to the recent 2003 national nutrition survey conducted by the Food and
Nutrition Research Institute, Department of Science and Technology, 37 out of 100
Filipinos are anemic (Food and Nutrition Research Institute 2006). Rice is the staple
food of most Filipinos. It contains 200300 mg/100 g phytic acid but was not found to
inhibit iron absorption especially in the presence of meat, sh or poultry and the
ascorbic acid present in fruits and vegetables in Filipino meals (Trinidad et al, 1986,
1989). However, it was found that rice-based meal containing 3,000 mg/100 g tannic
acid or greater inhibited iron absorption in regional meals in the Philippines (Trinidad
et al. 1986). Previous iron absorption studies in Filipinos from rice and rice-based
meals were carried out on milled rice but no research was done on brown rice of the
same variety. This leads to the hypothesis that brown rice may be better than milled rice
in terms of iron content and absorption.
The Asia Rice Foundation with the Philippine Rice Research Institute (PhilRice)
launched a brown rice popularization drive in 2001, based on nutritional considera-
tions: a higher content of vitamins and minerals, despite poorer acceptability and shelf-
life, as compared with milled rice. Studies on iron absorption from brown rice are
scarce. Brown rice has been shown to have greater iron availability in vitro than milled
rice but lower zinc and calcium availability (Feliciano 2001). However, in vitro
digestion and ferritin formation in cultured human intestinal Caco-2 cells of cooked
rice digests showed higher iron absorption (ferritin formed) on milling of ve brown
rice varieties (Prom-u-Thai et al. 2006). Studies conducted in Thailand on milled and
brown rice revealed that the percentage iron absorption from milled rice was greater
than that of brown rice (Tuntowiroon et al. 1990; Sirichakwal et al. 2006). However,
because of the higher iron content of brown rice, the absolute amount of iron absorbed
from the milled rice can be lower than brown rice (Sirichakwal et al. 2006). Brown rice,
in comparison with milled rice, contains more dietary ber in addition to phytic and
tannic acids (Miyoshi et al. 1986, 1987). Dietary ber has been shown to interfere with
mineral absorption in the small intestine. Nevertheless, if the ber is fermentable in the
colon it can release the mineral for absorption in the colon (Thompson et al. 1991;
Trinidad et al. [1996a],[b]). The objective of the present study is to determine the
absorption of iron from brown rice/brown rice-based meal and milled rice/milled rice-
based meal of the same variety in humans.
Materials and methods
Test foods
Brown rice (PSB Rc72H), milled rice (PSB Rc72H), Hasa-hasa (Rastrelliger brachyo-
somus), kangkong (Ipomoea batatas aquatica), and kalamansi (Citrus microcarpa)
were used as the test foods in the study. Rough rice (F
2
) from the 2002 dry season
crop of PhilRice was decupled in a Satake THU 35 type dehuller and one-half of the
brown rice was milled in a Satake One-Pass table-type SKD mill DCK L2 at 9.3%
reduction of 100-grain weight. One hundred grams of brown rice was soaked in 350 ml
distilled water for 30 min and boiled in an individual aluminum pot for each
subject. Similarly, 100 g milled rice was cooked without soaking in 300 ml distilled
water. The amount of water used for brown rice and milled rice differed because
Iron absorption from brown and milled rice 689
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brown rice needed more water to cook. The other ingredients were purchased from the
Bicutan, Taguig Market and were cooked separately from the rice, as described by
Trinidad et al. (2002). A different portion of the cooked meal was homogenized and
freeze-dried for analysis.
Subjects
All subjects were male, aged 2439 years, with a body mass index of 24.4 ±1.0 kg/m
2
and in the normal range of hemoglobin (15.0 ±0.2 g/dL) and hematocrit (51.5 ±1.8%).
Analytical methods
Cooked and freeze-dried brown rice/brown rice-based meal and milled rice/milled rice-
based meal of the same variety were analyzed for iron (Association of Ofcial Analytical
Chemists [1995a]), non-heme iron (Torrance and Bothwell 1968), phytic acid (Asso-
ciation of Ofcial Analytical Chemists 1986), tannic acid (Earp et al. 1981), dietary
ber (e.g. total, soluble and insoluble) (Association of Ofcial Analytical
Chemists [1995b]) and proximate analysis (Association of Ofcial Analytical
Chemists 2000).
Protocol of the study
After an overnight fast, blood was drawn from the subjects for baseline data. The
subjects were randomly fed with meal A consisting of brown rice extrinsically labeled
with 0.5 mCi/subject
59
Fe (Perkin Elmer, Boston, MA, USA) and with meal B
consisting of brown rice extrinsically labeled with 1.0 mCi/subject
55
Fe (Perkin Elmer),
sh and vegetables, on two consecutive days in the order AB. After 14 days, blood was
drawn from each subject for radioactivity measurements. Subjects were randomly fed
again with milled rice labeled with 0.5 mCi/subject
59
Fe (meal C) and with labeled
milled rice (1.0 mCi/ subject
55
Fe), sh and vegetables (meal D), on two consecutive
days in the order CD. After 14 days, blood was drawn and a reference dose of labeled
iron (0.5 mCi/subject
59
Fe), consisting of ferrous sulfate and ascorbic acid was
administered to each subject. After 14 days, blood was drawn again from each subject.
Blood samples were read in a liquid scintillation counter after digestion using the
modied method of Eakins and Brown (1966). No food or drink was taken by the
subjects until 4 h after ingestion of the labeled food for all treatments. The protocol of
the study was cleared by the Food and Nutrition Research Institute Human Ethics
Committee.
Statistical analysis
Because the distribution of iron absorption data is positively skewed when expressed as
a percentage of the administered dose, the data were transformed to logarithms and
results reconverted to an anti-logarithm to recover the original units. Differences in
iron absorption between treatments and subjects were determined by repeated-mea-
sures analysis of variance and Duncans multiple range tests using the SAS Program
(Statistical Analysis System, Cary, NC, USA).
690 T. P. Trinidad et al.
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Results
Results were expressed as the mean ±standard error of the mean. Table I presents the
nutrient analysis and iron content of rice samples tested. Brown rice had signicantly
higher ash, fat and iron content than milled rice while moisture and carbohydrate
content were signicantly higher in milled rice (P<0.05). Brown rice had signicantly
greater amounts of total and insoluble dietary ber than its respective milled rice
(Table I; P<0.05). Milled rice did not contain soluble dietary ber. The tannic acid
content of brown rice (56.9 ±3.2 mg/100 g) and milled rice (21.3 ±2.3 mg/100 g) was
below 100 mg, suggesting that brown rice and milled rice are not good sources of tannic
acid. On the other hand, brown rice had signicantly greater phytic acid
(290.1 ±18.0 mg/100 g) content than milled rice (84.0 ±12.4 mg/100 g; P<0.05).
Brown rice-based meal had signicantly greater tannic acid and phytic acid contents
(198.7 ±0.88 mg/100 g and 317.4 ±0.96 mg/100 g, respectively) than milled rice-based
meal (165.2 ±0.81 mg/100 g and 140.1 ±0.16 mg/100 g, respectively).
The iron absorption from rice samples and meals is shown in Table II. The
percentage iron absorption was higher from milled rice than from brown rice. However,
the absolute amount of iron absorbed from rice samples revealed that brown rice did
not signicantly differ from milled rice (Table II; P<0.05, n=12). Iron absorbed from
brown/milled rice-based meal was signicantly higher than that of brown/milled rice
(P<0.05). This showed that iron absorbed from rice-based meals was increased by their
higher iron content and in the presence of iron enhancers (e.g. sh, vegetables and
citrus fruit juice). The heme iron content of sh (total iron non-heme iron; Table II)
given per subject was 0.2 mg. The vegetable (kangkong) used in the study contained
30 mg ascorbic acid/100 g, and kalamansi juice, a citrus fruit added to the vegetable
used in the study, contained 45 mg ascorbic acid/100 g (Food and Nutrition Research
Institute 1997). The total intake of ascorbic acid per subject from kangkong (44 g) and
kalamansi (10 g) was 17.7 mg.
Discussion
Iron absorption studies from brown rice are scarce. Studies performed in Thailand
revealed a greater percentage iron absorption from milled rice than from brown rice
(Tuntowiroon et al. 1990; Prom-u-Thai et al. 2006); however, because of the high
Table I. Nutrient content and total iron of cooked and freeze-dried brown and milled rice.
Parameter Brown rice Milled rice
Moisture (g/100 g) 5.3 ±0.1
b
6.0 ±0.1
a
Ash (g/100 g) 1.3 ±0.0
a
0.2 ±0.0
b
Fat (g/100 g) 2.5 ±0.0
a
1.1 ±0.1
b
Protein (g/100 g) 6.1 ±0.2
a
5.9 ±0.0
a
Carbohydrates (g/100 g) 84.8 ±0.3
b
86.8 ±0.2
a
Dietary ber (g/100 g) 4.6 ±0.2
a
1.7 ±0.1
b
Insoluble ber (g/100 g) 3.6 ±0.1
a
1.7 ±0.1
b
Soluble ber (g/100 g) 1.0 ±0.1 0.0
Iron (mg/100 g) 1.1 ±0.1
a
0.6 ±0.1
b
Data presented is expressed as mean ±standard error of the mean n=4. Data in the same row with different
superscript letters denote signicant differences at P<0.05.
Iron absorption from brown and milled rice 691
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iron content of brown rice, iron absorbed from brown rice showed no signicant
differences with that of milled rice (Sirichakwal et al. 2006).
This study revealed similar results to those of Thailand. Iron absorbed from brown
rice and milled rice of the same variety as well as their respective rice-based meals did
not differ signicantly, despite the lower percentage iron absorption from brown rice.
This was also attributed to the signicantly higher iron content of brown rice than its
respective milled rice (Table II; P<0.05). The signicant increase in iron absorbed
from brown rice/milled rice-based meals than brown rice/milled rice alone may be due
to the presence of heme iron from sh, and ascorbic acid in vegetables and citrus fruit
juice. Heme iron is readily and well absorbed and it also promotes the absorption of
non-heme iron present in a meal (Lynch and Stoltzfus 2003). The quantitative
recommendation for ascorbic acid effect on iron absorption was based on an ascorbic
acid to iron molar ratio between 2.1 and 4.1 (Lynch and Stoltzfus 2003). The ascorbic
acid to iron molar ratio from our study showed 1.5:1 for brown rice-based meal and 2:1
for milled rice-based meal. The vegetable in the meal was steamed, suggesting less or
no loss of ascorbic acid. The citrus fruit juice was given raw. On the other hand,
Filipino meals contained 200300 mg/100 g phytic acid but were not found to inhibit
iron absorption especially in the presence of meat, sh or poultry and of ascorbic acid
present in fruits and vegetables (Trinidad et al. 1986, 1989). Also, rice-based meal with
less than 3,000 mg/100 g tannic acid did not inhibit iron absorption in regional meals in
the Philippines (Trinidad et al. 1989). Brown rice, in comparison with milled rice,
contains signicantly greater dietary ber (Table I) in addition to phytic and tannic
acids. Dietary ber has been shown to interfere with mineral absorption in the small
intestine. Nevertheless, if the ber is fermentable in the colon it can release the mineral
for absorption in the colon (Thompson et al. 1991; Trinidad et al. [1996a],[b]). Results
showed that the dietary ber, phytic acid and tannic acid from brown rice did not
interfere with iron absorption.
In conclusion, the iron absorbed from brown rice and milled rice of the same variety
did not differ signicantly, as well as that from the respective meals. There was a
signicant increase in iron absorbed when both brown rice and milled rice were served
with sh, vegetables and citrus fruit juice.
Acknowledgements
The study was partially funded by PhilRice through its Executive Director, Dr
Leocadio S. Sebastian. The authors acknowledge the technical assistance of Maureen
Ugat, Zoilo B. Villanueva and Paz S. Lara of the Food and Nutrition Research
Institute, Department of Science and Technology.
Table II. Iron absorption from cooked rice samples and meals.
Test food
Food
intake (g)
Total iron per
intake (mg)
Non-heme iron
per intake (mg)
Iron
absorption (%)
Iron
absorbed (mg)
Brown rice 228.9 ±3.4
b
2.51 ±0.02
c
2.31 ±0.02
c
5.5 ±1.2
c
0.13 ±0.02
b
Brown rice-based meal 322.9 ±5.2
a
3.81 ±0.01
a
3.61 ±0.01
a
9.9 ±2.2
b
0.36 ±0.04
a
Milled rice 221.4 ±5.0
b
1.33 ±0.01
d
1.33 ±0.01
d
10.3 ±2.3
b
0.14 ±0.02
b
Milled rice-based meal 315.8 ±5.3
a
2.83 ±0.01
b
2.63 ±0.01
b
13.4 ±3.0
a
0.35 ±0.03
a
Data presented as is expressed mean ±standard error of the mean n=12. Data in the same column with
different superscript letters denote signicant differences at P<0.05.
692 T. P. Trinidad et al.
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... Overall, the higher content of all the three micronutrient cations, viz., Fe, Zn and Cu in the unpolished and polished grains of TP can be linked with higher level of expression of fer2, ZIP and NAS3. Moreover, polished counterparts of all the varieties showed micronutrient loss as compared to unpolished grains, supporting the observation byTrinidad et al. (2009), where higher Fe content in brown/unpolished rice was reported when compared against the polished/milled counterparts. The PCA revealed closer relation between Fe and Zn in comparison to Cu. ...
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... Irrespective of grain type, Karimundaga (56.88 mg) recorded maximum tannic acid, whereas Gamnad batta (25.74 mg) recorded minimum. The results obtained in the present study are in accordance with the values reported by Trinidad et al., (2009). In their study, tannic acid contents in brown rice (56.9 ± 3.2 mg/100 g) was significantly higher than milled rice (21.3 ± 2.3 mg/100 g, P<0.05). ...
... Therefore, a deficiency in one likely predicates the other, unless there is a specific cause for either condition [16]. Anemia is one of the major problems in tribal population of Bangladesh [17] due to genetic disorder in hemoglobin gene and lack of nutrition due to extreme poverty [18]. A contributing factor to this is the presence of various hemoglobin disorders [19]. ...
... The mere presence of a mineral does not mean that it will be absorbed. For example, although comparisons of mineral concen-trations in whole grain foods show them to be much higher than those in refined grains, the actual amount absorbed may differ little due to various factors impacting bioavailability (62). In some cases the mineral in the whole grain kernel is inaccessible or is bound to the fiber or phytic acid, which inhibits the absorption of iron, calcium, zinc, and magnesium (63). ...
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The AACCI Whole Grains Working Group supports increasing whole grain intake through the use of intact whole grains and grains milled with the use of stones and steelrollers in single-stream milling, multiple-stream milling where streams are recombined at the mill, and multiple-stream milling in which whole grains are responsibly reconstituted "at the mixing bowl."
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To address many current claims that disparage and discourage the ingestion of carbohydrates (CHOs), wheat, and cereal grains, as well as to celebrate the versatility, nutritional and health benefits, and contribution of these foods to the world food supply, we felt compelled to defend their role in the diet and write a series of reviews. Where data exist, cereal grains and wheat as a source of CHOs and other important nutrients are the focus. In this second review, grain- and wheat-based staples are shown to be important contributors of CHOs (including cereal fiber), as well as necessary proteins, vitamins, and minerals, as part of a balanced diet for most healthy individuals. The terminology associated with grains and whole grains and their processing also is discussed and defined. Dietary fiber and resistant starch are defined, and a whole grain food characterization is provided. Clear delineation of terms is critical because they differ from country to country and are a source of consumer confusion in nutrition education and labeling. CHO-rich staple foods, including those from an array of whole and enriched/fortified refined grains, are inexpensive sources of a wide variety of nutrients, dietary fibers, and phytochemicals. This combination uniquely positions them as a source of nutrition to both sustain and nourish a global population.
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Iron (Fe) bioavailability in unpolished, polished grain and bran fraction of five rice genotypes with a range of Fe contents was measured by in vitro digestion and cultured Caco-2 cells of cooked grain. There was a significant difference in Fe bioavailability among the five rice genotypes tested, in both the unpolished and polished grain. The range of Fe bioavailability variation in polished rice was much wider than that of unpolished, suggesting the importance of using Fe levels and bioavailability in polished rice grain as the basis for selecting high-Fe rice cultivars for both agronomic and breeding purposes. Milling and polishing the grain to produce polished (or white) rice increased Fe bioavailability in all genotypes. Iron bioavailability in polished rice was high in the UBON2 and Nishiki, intermediate in both IR68144 and KDML105, and low in CMU122. All genotypes had low bioavailability of Fe in bran fraction compared to unpolished and polished grain, except in CMU122. CMU122 contained the lowest level of bioavailable Fe in unpolished and polished grain and bran, because of the dark purple pericarp colored grain and associated tannin content. The level of bioavailable Fe was not significantly correlated with grain Fe concentration or grain phytate levels among these five genotypes tested. The negative relationship between Fe bioavailability and the levels of total extractable phenol was only observed in unpolished (r = −0.83**) and bran fraction (r = −0.50*). The present results suggested that total extractable phenol and tannin contents could also contribute to lowering bioavailability of Fe in rice grain, in addition to phytate. Copyright © 2006 Society of Chemical Industry
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The effects of rice fiber on fecal weight, transit time, frequency of defecations, digestibility of nutrients and blood status were investigated in 5 healthy young men. Each of them consumed a brown rice diet and then a polished rice diet for 2 weeks respectively. Both diets contained 1.2 g protein per kg body weight. The brown rice diet contained 2 times as much dietary fiber as the polished rice diet. When they consumed the brown rice diet, it showed an increase of fecal weight and decrease of digestibility of energy, nitrogen and fat. Nitrogen balance was not significantly different and kept zero balance on both diets. Concentration of plasma cholesterol was not significantly different. The results suggest that rice fiber produced an increase in fecal weight, which is assumed to be effective in preventing colonic disease in advanced countries and does not affect plasma lipid level.
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A method for the simultaneous determination of Fe55 and Fe59 in blood is described. After wet oxidation of the blood sample the iron is precipitated as ferric hydroxide. It is then converted to an insoluble white ferriphosphate complex by dissolving the hydroxide in phosphoric acid and adding a solution of ammonium chloride in absolute ethanol. The resulting precipitate is counted as a gel in a two-channel, liquid-scintillation spectrometer, set to count Fe59 alone in one channel and Fe55 plus a small percentage of Fe59 in the other channel. The counting efficiencies obtained are 19<ṡ4 per cent for Fe55 and 33ṡ;4 per cent for Fe59 with chemical yields of 95 per cent. The counting efficiency for Fe55 is greater by a factor 3 than the best value previously reported for liquid scintillation counting, with sources containing comparable amounts of inactive iron.
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An in vitro method simulating conditions in the small intestine and colon was used to study the effects of various carbohydrates on Ca release from basal diet (BD) containing dairy products. During enzymatic digestion of BD, 28.5 +/- 0.3% of the Ca was released. This was reduced by 3, 22 and 27% by adding bread, psyllium or pectin to BD, respectively (P < 0.05). After enzymatic digestion, the residue from BD was fermented releasing 11.9 +/- 1.2% of the Ca, a value which was significantly less than with pectin (13.7 +/- 0.9%) and greater than with psyllium (4.4 +/- 0.2%) addition. The total Ca release ranged from 26.5 +/- 0.8 to 42.2 +/- 1.0% with bread>BD>pectin>psyllium. Lactulose did not differ significantly from BD. These results suggest that carbohydrates may bind Ca and reduce its availability for absorption in the small intestine. However, if the carbohydrate is fermented, bound Ca may be released for potential absorption in the colon, whereas less fermented carbohydrates may continue to bind Ca in the colon. The in vitro method described may be useful for estimating total Ca availability. However, studies in humans are required to validate these results.