Improve Iron Absorption Research Articles

Influence of Vegetable Protein Sources on Trace Element and Mineral Bioavailability

Vegetable protein sources are often mixed with cereals for complementary feeding. Both contain high levels of phytic acid, which can inhibit trace element and mineral absorption. In adults, phytic acid has been reported to inhibit the absorption of iron, zinc, calcium and manganese but not copper. There are far fewer studies in infants. Phytic acid is a strong inhibitor of iron absorption in both infants and adults, but its influence on zinc absorption in infants seems to be modest and perhaps most important in children recovering from infection. The influence of phytic acid on calcium and magnesium absorption would seem of minor importance. Because iron and zinc deficiencies are widespread in infants and young children in developing countries, the bioavailability of iron and zinc from complementary food is a major concern. Iron absorption may be as low as 2-3% from porridge based on whole-grain cereals and legumes (phytic acid approximately 1 g/100 g) even in iron-deficient subjects. Decreasing phytic acid by 90% ( approximately 100 mg/100 g dried product) would be expected to increase absorption about twofold and complete degradation perhaps fivefold or more. More modest reductions in phytic acid content may not usefully improve iron absorption. Complete enzymatic degradation of phytic acid is recommended. If this is not possible, it is recommended that the molar ratio of phytic acid to iron in an iron-fortified food be <1, preferably <0.5. At these low levels of phytic acid (20-30 mg/100 g dried product), zinc absorption should be satisfactory.

Phytogenic and microbial phytases in human nutrition

SummaryPhytate (inositol hexa phosphate) hydrolysis can occur during food preparation and production and in the intestine, either by phytase from plants, yeasts or other micro‐organisms. This degradation is of nutritional importance, because removal of phosphate groups from the inositol ring results in an increased bioavailability of essential dietary minerals. To substantially improve iron absorption the degradation has to be virtually complete. Food processing techniques increasing the activity of the naturally occurring plant phytases are soaking, malting, hydrothermal treatment and fermentation. An alternative is addition of phytases or micro‐organisms producing phytase. Phytate degradation in the stomach and small intestine occurs as a result of activity of dietary phytase of plant or microbial origin. The plant phytase is less stable than fungal phytase in the physiological conditions of the intestine. Biotechnologically produced phytases may be possible for use tomorrow in food processing as well as plant raw material and starter cultures with inserted phytase genes.

The Effect of Different Iron Fortificants on Iron Absorption from Iron-Fortified Rice

Iron absorption from rice fortified with different iron fortificants, e.g., ferrous sulfate (FeS04), sodium iron EDTA (NaFeEDTA), ferrous fumarate (FeFum), and ferrous bisglycinate (FeBis) was determined using an in vitro enzymatic digestion method simulating conditions in the small intestine and an in vivo method using radioisotope techniques. The in vitro method showed that the percentage of dialyzable iron from NaFeEDTA (15.7 +/- 0.9) and FeS04-fortified rice (13.2 +/- 1.5) was significantly greater than that from FeFum (6.4 +/- 0.6; p < .05) and FeBis fortified rice (3.3 +/- 0.8; p < .05). Iron absorption in vivo was investigated from FeS04 and NaFeEDTA fortified rice with and without fish and vegetables in 10 borderline iron-deficient subjects. Iron absorption (mg) from NaFeEDTA fortified rice (0.44 +/- 0.11) was significantly greater than from FeS04-fortified rice (0.22 +/- 0.05; p < .05) and the unfortified rice (0.17 +/- 0.02; p < .05). Iron absorption (mg) from a meal consisting of iron-fortified rice, fish, and vegetables was significantly greater from NaFeEDTA (0.88 +/- 0.24) and FeS04 (0.67 +/- 0.10) -fortified rice than from the unfortified rice (0.41 +/- 0.08; p < .05). This study concluded that both NaFeEDTA and FeSO4 are effective iron fortificants for rice. The binder used in the study may have a significant role in the release of iron from iron-fortified rice for absorption. Further studies on the use of other binders to maximize iron release and minimize iron loss during cooking should be conducted to improve iron absorption from the fortified rice/rice-fish-vegetable meals. Results from this study can be used as a basis for food iron fortification programs as well as in the establishment of recommended dietary allowances for iron among Filipinos.

Improving iron absorption from a Peruvian school breakfast meal by adding ascorbic acid or Na2EDTA

Iron-fortified school breakfasts have been introduced in Peru to combat childhood iron deficiency. We evaluated whether iron absorption from a school breakfast meal was improved by increasing the ascorbic acid content or by adding an alternative enhancer of iron absorption, Na2EDTA. In a crossover design, iron absorption from test meals was evaluated by erythrocyte incorporation of 58Fe and 57Fe. The test meals (wheat bread and a drink containing cereal, milk, and soy) contained 14 mg added Fe (as ferrous sulfate) including 2.0-2.6 mg 58Fe or 4.0-7.0 mg 57Fe. Geometric mean iron absorption increased significantly from 5.1% to 8.2% after the molar ratio of ascorbic acid to fortification iron was increased from 0.6:1 to 1.6:1 (P < 0.01; n = 9). Geometric mean iron absorption increased significantly from 2.9% to 3.8%, from 2.2% to 3.5%, and from 2.4% to 3.7% after addition of Na2EDTA at molar ratios relative to fortification iron of 0.3:1, 0.7:1, and 1:1, respectively, compared with test meals containing no added enhancers (P < 0.01; n = 10 for all). Iron absorption after addition of ascorbic acid (molar ratio 0.6:1) was not significantly different from that after addition of Na2EDTA (molar ratio 0.7:1). Ascorbic acid and Na2EDTA did not differ significantly in their enhancing effects on iron absorption at molar ratios of 0.6:1 to 0.7:1 relative to fortification iron. Additional ascorbic acid (molar ratio 1.6:1) increased iron absorption significantly. Increasing the molar ratio of Na2EDTA to fortification iron from 0.3:1 to 1:1 had no effect on iron absorption.

The HFE Gene of Browsing and Grazing Rhinoceroses: A Possible Site of Adaptation to a Low-Iron Diet

ABSTRACTWhen rhinoceros species that are browsers in the wild are fed in captivity they become iron overloaded. Presumably, their iron-absorptive mechanisms have evolved to become highly efficient. In humans, mutations of the HFE gene cause increased iron absorption. To determine whether the HFE gene of rhinoceroses has undergone mutation as an adaptive mechanism to improve iron absorption from iron-poor diets, we have sequenced the entire coding region of the HFE genes of four species of rhinoceros. Two of these were browsing species and two were grazing species. Although the HFE gene has been well preserved across species, numerous nucleotide differences were found between rhinoceros and human or mouse, some of which changed deduced amino acids. Of these mutations, only one found in the black rhinoceros appears to be a viable candidate mutation that might adversely affect HFE function. This mutation, S88T, is in a highly conserved region that is involved in the interaction between transferrin receptor and HFE.

Inositol phosphates with different numbers of phosphate groups influence iron absorption in humans

Inositol hexaphosphate (IP(6)) is a well-known inhibitor of iron absorption, whereas the effects of the less-phosphorylated derivatives of IP(6) are less known. The objective was to investigate the effects of inositol tri-, tetra-, and pentaphosphates (IP(3), IP(4), and IP(5), respectively) on iron absorption in humans. Iron absorption was measured in 5 experiments from single meals by extrinsic labeling with (55)Fe and (59)Fe and determination of whole-body retention and the erythrocyte uptake of isotopes. In experiments 1-3 the meals contained white-wheat rolls to which 10 mg P as IP(5), IP(4), or IP(3), respectively, was added. Inositol 1,2,6-triphosphate [Ins(1,2, 6)P(3)] and a mixture of isomers of IP(4) and IP(5) were studied. White-wheat rolls contained 10 mg P as IP(3) + IP(4) and 2 mg P as IP(5) + IP(6) in experiment 4 and 20 mg P as IP(3) + IP(4) and 3 mg P as IP(5) + IP(6) in experiment 5; inositol phosphates were obtained via fermentation of sodium phytate. Each experiment had 8-11 subjects. In experiment 1, iron absorption was reduced by 39%, whereas there was no significant effect on iron absorption in experiments 2 and 3. In experiments 4 and 5, iron absorption was reduced by 54% and 64%, respectively, suggesting that IP(3) and IP(4) contributed to the inhibitory effect. IP(5) has an inhibitory effect on iron absorption, whereas IP(3) and IP(4) in isolated form have no such effect. IP(3) and IP(4) in processed food contribute to the negative effect on iron absorption, presumably by binding iron between different inositol phosphates. To improve iron absorption from cereals and legumes, degradation of inositol phosphates needs to be to less-phosphorylated inositol phosphates than IP(3).

Effect of genetically modified, low–phytic acid maize on absorption of iron from tortillas

BackgroundGenetically modified, low–phytic acid strains of maize were developed to enhance mineral absorption, but have not been tested previously in humans. ObjectivesWe evaluated the mineral and phytic acid contents of a low –phytic acid “flint” maize (LPM, the lpa-1-1 mutant)and its parent, wild–type strain (WTM) and measured iron absorption from tortillas prepared with each type of maize and from a reference dose of ferrous ascorbate. DesignProximate composition and mineral and phytic acid contents were measured by standard techniques. Iron absorption from tortillas was evaluated by using the extrinsic tag method and was measured as the incorporation of radiolabeled iron into the red blood cells of 14 nonanemic men 2 wk after intake. ResultsThe phytic acid content of LPM was 3.48 mg/g, <35% of the phytic acid content of WTM; concentrations of macronutrients and most minerals were not significantly different between strains. Iron absorption results were adjusted to 40% absorption of ferrous ascorbate. Iron absorption was 49% greater from LPM (8.2% of intake) than from WTM (5.5% of intake) tortillas (P < 0.001, repeated-measures analysis of variance). ConclusionConsumption of genetically modified, low–phytic acid strains of maize may improve iron absorption in human populations that consume maize–based diets. Am J Clin Nutr 1998;68:1123–7.

Knowledge and attitudes of Missouri physicians regarding meat

Society perceives the physician as an individual most knowledgeable in all aspects of human health including nutrition even though they lack academic preparation in nutrition and especially in foods. The objectives of this study were to determine physicians' knowledge of the nutritional benefits of meat, to examine the attitudes of physicians regarding beef consumption, and to determine the frequency that physicians refer clients to dietitians. Cardiovascular and family practice physicians (n=42) and fourth year medical students (n=43) completed a mail questionnaire. Respondents were asked to identify the important nutrients in lean cuts of meat and personal attitudes toward meat were examined. Both groups correctly identified meat as an important source of protein (98%); 44% incorrectly identified Vitamin A as an important nutrient in beef and poultry and 74% erroneously selected poultry products as the lowest in calories when selecting from specific poultry, prok, beef and cheese items. Scores on knowledge questions categorized into ‘nutrition’, ‘calorie/cholesterol’ and ‘combined’ were 45, 40 and 43%, respectively for physicians and 52, 40 and 43%, respectively for students. Attitudes toward meat were neutral (2.9; 1 = strongly disagree, 5 = strongly agree). Both groups agreed that beef can be part of a healthy diet (4.2) and that the meat industry produces leaner meat today than 30 years ago (4.0). They disagreed that a vegetarian diet is more healthy than one with meat (2.3). Physicians agreed more strongly (4.4) than students (4.1) that what a person eats influences the risk of coronary heart disease (p < .001), and they disagreed more strongly than students (2.3 vs. 2.7) that red meat can be eaten as often as poultry if fat is trimmed off (p < .05). A lack of knowledge was demonstrated by neutral responses to improved iron absorption from non-meat sources in the presence of meat in the same meal. Forty-eight percent of respondents identified a registered dietitian or themselves (34%) as the most likely person to provide nutrition counselling to patients. Frequency of referrals to a dietitian was 35, 59, and 6% for often, occasional or never, respectively. Results of this study provide valuable information for targeting future education of physicians and marketing strategies for dietitians.

Effects of vitamin C and iron and cadmium metabolism.

Toxic levels of dietary cadmium (5-200 ppm) interfered with iron absorption and produced an iron deficiency. Supplements of iron (particularly the divalent form) and ascorbic acid protected against the cadmium. With very low levels of dietary cadmium (about 0.06-0.08 ppm), typical of those in the diets of humans, supplements of iron(II) and ascorbic acid markedly decreased cadmium concentrations in the liver, kidney, and small intestine. Iron deficiency changed the distribution of cadmium within the body. The effect of ascorbic acid on cadmium metabolism appears to depend primarily, if not entirely, on its influence in improving iron absorption. Maintenance of modest iron stores appears to be very important in minimizing cadmium absorption.