Maternal hepcidin is associated with placental transfer of iron derived from dietary heme and nonheme sources

The determinants of placental transport of dietary iron remain largely uncharacterized. The objective of this research was to elucidate determinants of fetal Fe transfer from maternally ingested dietary heme and non-heme Fe. The study was undertaken in 19 pregnant females (16-32 y) who ingested intrinsically labeled (58)Fe-heme and a nonheme Fe source ((57)FeSO(4)) during the third trimester of pregnancy. At delivery, maternal and cord blood was obtained to assess neonatal (57)Fe and (58)Fe enrichment as a function of maternal/neonatal Fe status [serum ferritin (SF), transferrin receptor, hemoglobin (Hb), total body Fe, and hepcidin]. There was a greater percentage of maternally absorbed (58)Fe tracer present in the neonates compared to the (57)Fe tracer (5.4 ± 2.4 vs. 4.0 ± 1.6; P < 0.0001). Net dietary nonheme Fe (mg) and heme Fe (mg) transferred to the fetus were both inversely correlated with measures of maternal serum hepcidin (P = 0.002, r(2) = 0.43; P = 0.004, r(2) = 0.39) and SF (P = 0.0008, r(2) = 0.49; P = 0.003, r(2) = 0.41) and directly associated with neonatal Hb (P = 0.004, r(2) = 0.39; P = 0.008, r(2) = 0.35). The results of this study suggest that during pregnancy there appears to be preferential fetal use of maternally ingested Fe derived from a dietary, animal-based heme source compared to Fe ingested as ferrous sulfate. Maternal serum hepcidin and maternal/neonatal Fe status may play a role in placental uptake of dietary heme and nonheme Fe.     

Influence of prenatal iron and zinc supplements on supplemental iron absorption, red blood cell iron incorporation, and iron status in pregnant Peruvian women

BACKGROUND: It is estimated that 60% of pregnant women worldwide are anemic. OBJECTIVE: We aimed to examine the influence of iron status on iron absorption during pregnancy by measuring supplemental iron absorption, red blood cell iron incorporation, and iron status in pregnant women. DESIGN: Subjects were 45 pregnant Peruvian women (33+/-1 wk gestation), of whom 28 received daily prenatal supplements containing 60 mg Fe and 250 microg folate without (Fe group, n = 14) or with (Fe+Zn group, n = 14) 15 mg Zn, which were were consumed from week 10 to 24 of gestation until delivery. The remaining 17 women (control) received no prenatal supplementation. Iron status indicators and isotopes were measured in maternal blood collected 2 wk postdosing with oral (57Fe) and intravenous (58Fe) stable iron isotopes. RESULTS: Maternal serum ferritin and folate concentrations were significantly influenced by supplementation (P < 0.05). Serum iron was also significantly higher in the Fe than in the Fe+Zn (P < 0.03) or control (P < 0.001) groups. However, the supplemented groups had significantly lower serum zinc concentrations than the control group (8.4+/-2.3 and 10.9+/-1.8 micromol/L, respectively, P < 0.01). Although percentage iron absorption was inversely related to maternal serum ferritin concentrations (P = 0.036), this effect was limited and percentage iron absorption did not differ significantly between groups. CONCLUSIONS: Because absorption of nonheme iron was not substantially greater in pregnant women with depleted iron reserves, prenatal iron supplementation is important for meeting iron requirements during pregnancy.     

Comparison of the efficacy of wheat-based snacks fortified with ferrous sulfate, electrolytic iron, or hydrogen-reduced elemental iron: randomized, double-blind, controlled trial in Thai women

BACKGROUND: Although elemental iron powders are widely used to fortify cereal products, little data exist on their efficacy in humans. OBJECTIVE: We compared the efficacy of wheat-based snacks fortified with ferrous sulfate, electrolytic iron, or hydrogen-reduced iron in Thai women with low iron stores. DESIGN: A double-blind intervention was conducted in 18-50-y-old women (n = 330) randomly assigned into 4 groups to receive either no fortification iron or 12 mg Fe/d for 6 d/wk for 35 wk as ferrous sulfate, electrolytic iron, or hydrogen-reduced iron in a baked, wheat-flour-based snack. Snacks were not consumed with meals, and consumption was monitored. At baseline, 20 wk, and 35 wk, hemoglobin status and iron were measured and the groups were compared. RESULTS: Between baseline and 35 wk, geometric mean serum ferritin (SF) increased significantly in all 3 groups receiving iron (P < 0.01), and geometric mean serum transferrin receptor (TfR) decreased significantly in the groups receiving ferrous sulfate and electrolytic iron (P < 0.05). Calculated mean (+/-SD) body iron stores increased from 1.5 +/- 2.8 to 5.4 +/- 2.9 mg/kg in the ferrous sulfate group, from 1.5 +/- 3.5 to 4.4 +/- 3.6 mg/kg in the electrolytic iron group, and from 1.3 +/- 3.2 to 3.2 +/- 4.3 mg/kg in the hydrogen-reduced iron group (P < 0.01 for all 3 groups) but did not change significantly in the control group. CONCLUSIONS: Ferrous sulfate, electrolytic iron, and hydrogen-reduced iron, fortified into wheat-based snacks, significantly improved iron status. On the basis of the change in body iron stores during the 35-wk study, the relative efficacy of the electrolytic and hydrogen-reduced iron compared with ferrous sulfate was 77% and 49%, respectively.     

Interactions among dietary manganese, heme iron, and nonheme iron in women.

The relationship among dietary intake of heme iron, nonheme iron, and manganese on indexes of hematological and nutritional status in regard to manganese of 47 women consuming their typical diets was investigated. Increasing dietary iron intake, by consuming more nonheme iron in the diet, had questionable effects on hematological status (hematocrit values and ferritin and transferrin concentrations) and negative effects on nutritional status in regard to manganese (serum manganese, urine manganese, and lymphocyte manganese-dependent superoxide dismutase activity). In contrast, heme-iron intake was positively correlated with hematological status and had no consistent effect on nutritional status in regard to manganese. Differences in dietary manganese intake had no consistent effect on indices of manganese or iron status, possibly because foods that contain significant amounts of manganese (green vegetables, breads, and cereals) often contain significant amounts of nonheme iron. Thus, increasing dietary manganese intake by consuming these foods is apt to have limited impact on manganese status because of the interaction between nonheme iron and manganese.     

Calcium does not inhibit the absorption of 5 milligrams of nonheme or heme iron at doses less than 800 milligrams in nonpregnant women

Calcium is the only known component in the diet that may affect absorption of both nonheme and heme iron. However, the evidence for a calcium effect on iron absorption mainly comes from studies that did not isolate the effect of calcium from that of other dietary components, because it was detected in single-meal studies. Our objective was to establish potential effects of calcium on absorption of nonheme and heme iron and the dose response for this effect in the absence of a meal. Fifty-four healthy, nonpregnant women were selected to participate in 4 iron absorption studies using iron radioactive tracers. We evaluated the effects of calcium doses between 200 and 1500 mg on absorption of 5 mg nonheme iron (as ferrous sulfate). We also evaluated the effects of calcium doses between 200 and 800 mg on absorption of 5 mg heme iron [as concentrated RBC (CRBC)]. Calcium was administered as calcium chloride in all studies and minerals were ingested on an empty stomach. Calcium doses ≥1000 mg diminished nonheme iron absorption by an average of 49.6%. A calcium dose of 800 mg diminished absorption of 5 mg heme iron by 37.7%. In conclusion, we demonstrated an isolated effect of calcium (as chloride) on absorption of 5 mg of iron provided as nonheme (as sulfate) and heme (as CRBC) iron. This effect was observed at doses higher than previously reported from single-meal studies, starting at ~800 mg of calcium.     

Meat consumption in a varied diet marginally influences nonheme iron absorption in normal individuals

It is widely recognized that the intake of animal foods is the most important dietary determinant of the iron status of a population. The primary reason is the high bioavailability of heme iron, but it is also known from radiolabeled single-meal feeding studies in humans that muscle tissue facilitates absorption of nonheme iron. In the present study, we examined the effect of meat intake on nonheme iron absorption from a whole diet. Iron absorption was measured during 3 separate dietary periods in 14 volunteers (7 men and 7 women) by having them ingest a radioiron-labeled wheat roll with every meal for 5 d. The diet was freely chosen for the first dietary period and altered to eliminate or maximally increase the intake of muscle foods during the second and third periods. Nonheme iron absorption did not differ for the 3 dietary periods although the geometric mean of 4.81% when subjects consumed a freely chosen diet increased by 35% to 6.47% with maximum meat consumption (P = 0.075). When nonheme absorption was adjusted to normalize for differences in iron status using serum ferritin correction and the 3 absorption periods were pooled, multiple regression analysis indicated no significant relation with heme or nonheme iron, vitamin C, calcium, phosphorus, fiber, or tea content of the diet with the exception of animal tissue (P = 0.013). We conclude that the higher iron status associated with the consumption of an omnivorous diet is due more to the intake of heme iron than to the enhancing effect on nonheme iron absorption.     

Absorption of iron from recombinant human lactoferrin in young US women

BACKGROUND: Lactoferrin is a major protein component of human milk, and it binds iron with high affinity. Because the human small intestine has receptors for lactoferrin, a role for it in iron absorption has been suggested. OBJECTIVE: The objective was to study the absorption of iron from extrinsically labeled purified recombinant human lactoferrin produced in rice and to compare it with the absorption of iron from ferrous sulfate. DESIGN: On 2 occasions 4 wk apart, healthy young women (n = 20) were fed a standardized meal supplemented in randomized order with 59Fe as lactoferrin or as ferrous sulfate. Ten subjects received lactoferrin that had been heat-treated, and 10 subjects received untreated lactoferrin. Iron absorption was measured in a whole-body counter after 14 and 28 d and also was measured by red blood cell incorporation after 28 d. RESULTS: The difference in whole-body iron absorption between heat-treated (24.6 +/- 20.8%; n = 10) and untreated (16.2 +/- 4.4%; n = 10) lactoferrin was not significant. The difference in whole-body iron absorption between the groups given lactoferrin (20.4 +/- 15.3%; n = 20) or ferrous sulfate (18.8 +/- 13.2%; n = 20) also was not significant. Serum ferritin and iron absorption were inversely correlated in subjects when they received either lactoferrin or ferrous sulfate, which suggested that iron is absorbed from the 2 sources by a similar mechanism. CONCLUSIONS: Iron is equally well absorbed from lactoferrin (whether heat-treated or untreated) and ferrous sulfate. Thus, iron provided by dietary lactoferrin is likely to be well utilized in human adults.     

Reducing iron deficiency anemia in Bolivian school children: Calcium and iron combined versus iron supplementation alone

ObjectiveThe aim of this study was to determine the effect of combined calcium and iron versus single iron supplementation on iron status in Bolivian schoolchildren.MethodsChildren ages 6 to 10 y old (N = 195), were randomly assigned to receive either 700 mg Ca (as calcium carbonate) plus 30 mg Fe (as ferrous sulfate) (Ca + Fe group) or 30 mg Fe (as ferrous sulfate) (Fe group). The doses were administered daily, from Monday to Friday, between meals at school over 3 mo. Iron status was assessed at baseline and after intervention. Additionally, overall nutritional status was assessed by anthropometry and an estimation of dietary intake.ResultsAt baseline, the prevalence of anemia in the Ca + Fe group and the Fe group were 15% and 21.5%, respectively. After 3 mo follow-up, the prevalence of iron deficiency anemia dropped significantly (P < 0.001) to 3% in both groups (χ² = NS). Iron dietary intake was within recommended levels, but calcium intake only covered 39% of the Recommended Daily Intake.ConclusionCombined calcium and iron supplementation is equally as effective as single iron supplementation in reducing the prevalence of iron deficiency anemia in Bolivian school children.     

Adaptation in iron absorption: iron supplementation reduces nonheme-iron but not heme-iron absorption from food

BACKGROUND: Results of cross-sectional studies suggest that in healthy people, iron absorption adapts to meet physiologic needs and stabilize iron stores, but this has not been adequately tested in longitudinal studies. OBJECTIVE: We tested whether heme- and nonheme-iron absorption decrease in response to increased iron intake and whether iron stores reach a steady state. DESIGN: In a randomized, placebo-controlled trial, heme- and nonheme-iron absorption by healthy men and women (n = 57) were measured before and after 12 wk of supplementation with 50 mg Fe/d as ferrous sulfate. Serum and fecal ferritin were measured during supplementation and for 6 mo thereafter. RESULTS: Initially, both heme- and nonheme-iron absorption were inversely associated with serum ferritin concentration. Volunteers who took iron supplements, even those with serum ferritin <21 microg/L (n = 5), adapted to absorb less nonheme iron (3.2% at week 12 compared with 5.0% at week 0, P: < 0.001) but not less heme iron from a beef-based meal. Serum ferritin concentration was slightly but significantly higher after iron supplementation than after placebo (difference = 13 microg/L). This higher ferritin concentration persisted for >/=6 mo after supplementation, except in subjects with low iron stores, whose serum ferritin returned to baseline within 3 mo. Fecal ferritin excretion increased 2.5-fold (P: < 0.05) during supplementation. CONCLUSIONS: Healthy individuals, even those with low iron stores, had reduced nonheme-iron absorption from food in response to iron supplementation. Despite this partial adaptation, iron stores were greater after iron supplementation than after placebo and this difference was sustained, except in individuals with the lowest iron stores.     

Women with low iron stores absorb iron from soybeans

BACKGROUND: Worldwide, 30% of the population, a greater proportion of whom are women and children, is iron deficient. Soybeans are a major source of nonheme iron in many human diets, but information on iron bioavailability is still conflicting. Because much of soybean iron is in ferritin [distinct from the poorly bioavailable iron in cereals resulting from interactions between calcium, Fe(III), phytate, and proteins in the meal], soybeans provide a target for manipulating seed iron composition to achieve increased iron bioavailability. OBJECTIVE: The aim was to reevaluate soybean iron bioavailability. DESIGN: Eighteen women, most with marginal iron deficiency, consumed meals with intrinsically labeled ((55)Fe) soybeans (hydroponically grown and nonnodulating) as soup (n = 11) or muffins (n = 7) and a reference dose of (59)Fe as ferrous sulfate in ascorbate solution. The radioactivity in red cells was measured 14 and 28 d later. RESULTS: The mean (55)Fe absorption from either soup or muffins was 27% and that from the reference dose was 61%. (55)Fe was distributed approximately equally between protein (49.3 +/- 3.0%) and phytate, a contrast with nodulating soybeans likely caused by a high phosphate content in the growth medium. There was an expected inverse correlation (r = -0.793, P < 0.001) between red cell radioactivity and serum ferritin concentration. CONCLUSIONS: These results show that soybeans appear to be a good source of nutritional iron in marginally iron-deficient individuals. More study is needed on the effect of plant nodulation on the form of soybean iron, aimed at enhancing bioavailability to combat iron deficiency in at-risk populations.     

Daily iron supplementation is more effective than twice weekly iron supplementation in pregnant women in Pakistan in a randomized double-blind clinical trial

In the context of limited effectiveness of iron supplementation programs, intermittent iron supplementation is currently under debate as a possible alternative strategy that may enhance the effectiveness of operational programs. This field-based trial assessed the outcome of twice weekly iron supplementation compared to daily in Pakistan. A double-blind, randomized, clinical trial was conducted in Northern Pakistan. Anemic pregnant women (n = 191) were assigned to receive daily (200 mg ferrous sulfate) or twice weekly (2 x 200 mg ferrous sulfate) iron supplementation. Hemoglobin was measured at baseline and at 4-wk intervals for up to 12 wk. Serum ferritin was measured at baseline and 8 or 12 wk. Analysis was by intention to treat. The two groups did not differ in age, parity, sociodemographic characteristics, hemoglobin or serum ferritin concentrations at baseline. Women who received iron daily had a greater rise in hemoglobin compared with women who received iron twice weekly (17.8 +/- 1.8 vs. 3.8 +/- 1.2 g/L, P < 0.001). The serum ferritin concentrations increased by 17.7 +/- 3.9 microgram/L (P < 0.001) in the daily supplemented group and did not change in the twice weekly group. Daily iron supplementation remained superior to twice weekly supplementation after controlling initial hemoglobin Z-scores and duration of treatment. The body mass index (BMI) modified the effect of daily versus twice weekly iron supplementation. For every unit increase in BMI, the difference between the two treatment groups was reduced by 0.0014 (final hemoglobin Z-score; P = 0.027). We recommend continuation of daily iron supplementation as opposed to intermittent iron supplementation in pregnant women in developing countries.     

High-, but not low-bioavailability diets enable substantial control of women's iron absorption in relation to body iron stores, with minimal adaptation within several weeks

BACKGROUND: Adaptation of iron absorption in response to dietary iron bioavailability is less likely in premenopausal women, who generally have lower iron stores, than in men. OBJECTIVE: The objective of the study was to ascertain whether iron absorption in women adapts to dietary iron bioavailability and whether adaptation reflects altered absorptive efficiency or adjustment to specific inhibitors or enhancers of absorption. DESIGN: Heme- and nonheme-iron absorption from either high- or low-bioavailability diets was measured at 0 and 10 wk in premenopausal women as they consumed one of the diets for 12 wk (randomized 2 x 2 factorial design). The high- and low-bioavailability diets contained similar amounts of total iron, as 13.1 and 14.8 mg/d nonheme and 2.0 and 0.3 mg/d heme iron, respectively, and they differed in contents of meat, ascorbate, whole grains, legumes, and tea. RESULTS: In premenopausal women, the efficiency of nonheme-iron absorption (P = 0.06, two-tailed test), but not of heme-iron absorption, tended to adapt in response to a 12-wk difference in dietary iron bioavailability, whether absorption was tested with high- or low-bioavailability menus. Bioavailability, but not adaptation, substantially influenced total iron absorption (approximately 6-fold). In contrast with iron absorption from the low-bioavailability diet, that from the high-bioavailability diet consistently was inversely associated with serum ferritin. CONCLUSION: Only the high-bioavailability diet enabled women to absorb more iron in relation to their low iron stores. Women consuming the high-bioavailability diet absorbed up to 4.5 mg (30-35%) dietary iron with minimal influence of the diet consumed during the previous 10 wk.     

Diet and iron status of nonpregnant women in rural Central Mexico

BACKGROUND: Few studies have examined the relation of iron status to diet in populations from developing countries with high levels of iron deficiency and diets of poor quality. OBJECTIVE: The objective was to identify nutrients, dietary constituents, and foods that are associated with better iron status in a rural Mexican population. DESIGN: A prospective cohort study was conducted in rural central Mexico. The subjects were 125 nonpregnant women aged 16-44 y. During the 12 mo before blood collection, food intakes were assessed repeatedly by a combination of dietary recalls, food weighing, and food diaries [mean (+/-SD) days of food intake data: 18.8 +/- 5.9 d]. Hemoglobin, hematocrit, and plasma ferritin were measured at the end of the study. RESULTS: Higher plasma ferritin concentrations were associated with greater intakes of nonheme iron and ascorbic acid after control for age, BMI, breast-feeding, season, and the time since the birth of the last child. Higher ascorbic acid intakes, but not higher intakes of heme and nonheme iron, predicted a lower risk of low hemoglobin and hematocrit values after control for the background variables. Consumption of the alcoholic beverage pulque predicted a lower risk of low ferritin and low hemoglobin values. Seasonal variation in ferritin, hemoglobin, and hematocrit values was observed. CONCLUSION: Better iron status was associated with greater intakes of foods containing nonheme iron and ascorbic acid. PULQUE:a beverage containing iron, ascorbic acid, and alcohol-may influence the iron status of women in rural central Mexico.     

Maternal iron status influences iron transfer to the fetus during the third trimester of pregnancy

BACKGROUND: The effect of maternal iron status on fetal iron deposition is uncertain. OBJECTIVE: We used a unique stable-isotope technique to assess iron transfer to the fetus in relation to maternal iron status. DESIGN: The study group comprised 41 Peruvian women. Of these women, 26 received daily prenatal supplements containing iron and folate (n = 11; Fe group) or iron, folate, and zinc (n = 15; Fe+Zn group) from week 10-24 of pregnancy to 1 mo postpartum. The remaining 15 women (control group) received iron supplementation only during the final month of pregnancy. During the third trimester of pregnancy (+/- SD: 32.9 +/- 1.4 wk gestation) oral 57Fe (10 mg) and intravenous 58Fe (0.6 mg) stable iron isotopes were administered to the women, and isotope enrichment and iron-status indicators were measured in cord blood at delivery. RESULTS: The net amount of 57Fe in the neonates' circulation (from maternal oral dosing) was significantly related to maternal iron absorption (P < 0.005) and inversely related to maternal iron status during the third trimester of pregnancy: serum ferritin (P < 0.0001), serum folate (P < 0.005), and serum transferrin receptors (P < 0.02). Significantly more 57Fe was transferred to the neonates in non-iron-supplemented women: 0.112 +/- 0.031 compared with 0.078 +/- 0.042 mg in the control group (n = 15) and the Fe and Fe+Zn groups (n = 24), respectively (P < 0.01). In contrast, 58Fe tracer in the neonates' circulation was not significantly related to maternal iron status. CONCLUSION: The transfer of dietary iron to the fetus is regulated in response to maternal iron status at the level of the gut.     

Serum iron curves can be used to estimate dietary iron bioavailability in humans

Erythrocyte incorporation of isotopic iron (Fe) is the standard method for assessing iron bioavailability, but the process is expensive, technically difficult, and gives no information on the kinetics of absorption. The main objective of this study was to validate serum Fe curves as measures of dietary iron absorption because previous work demonstrated that serum iron curves can be generated with iron doses as low as 5-20 mg and that up to 20 mg iron can be added to meals without affecting relative absorption. In 3 studies, groups (n = 10, 10, 21) of Fe-deficient, mildly anemic women consumed meals of varying calculated Fe bioavailability, with and without added ferric chloride (10 mg Fe). Blood samples were collected at baseline and every 30 min for 4 h after the meal. Serum Fe concentrations were measured. Areas under the serum Fe curves and peak concentrations were used in different models to estimate Fe absorption and uptake. In 21 subjects, (58)Fe-enriched ferric chloride was added to the meals, and blood was taken 2 wk later to calculate red cell isotope incorporation. The addition of 10 mg Fe to test meals produced measurable serum iron curves even when the meal Fe bioavailability was low. Serum Fe curves were highly reproducible and were affected as expected by food composition. Even the single measurement at the estimated time of peak iron concentration was correlated significantly with erythrocyte incorporation of (58)Fe (r = 0.72, P < 0.0001). Hence the extent and rate of absorption of nonheme iron from meals, rather than in individuals, can be investigated with such subjects without the need for isotopes.     

Calcium supplementation: effect on iron absorption

The influence of calcium supplements on the absorption of dietary nonheme iron and of iron supplements was evaluated in 61 normal volunteer subjects by use of a double-radioisotope technique. When taken without food, calcium carbonate did not inhibit the absorption of ferrous sulphate with doses of either 300 mg Ca and 37 mg Fe or 600 mg Ca and 18 mg Fe. However, at the latter levels, calcium citrate and calcium phosphate reduced iron absorption significantly by 49% and 62%, respectively. All calcium supplements inhibited absorption of the iron supplement when taken with food. The absorption of dietary nonheme iron was also inhibited by all three supplements. This inhibition was less pronounced from a meal of high iron availability and low calcium content (28%) than from a breakfast meal of low iron availability and high calcium content (55%). These results suggest that taking regular calcium supplements with meals makes it more difficult for women to meet their daily iron requirement.     

Initial uptake and absorption of nonheme iron and absorption of heme iron in humans are unaffected by the addition of calcium as cheese to a meal with high iron bioavailability

BACKGROUND: Quantitative data on the mucosal uptake and serosal transfer of nonheme-iron absorption in humans and the effects of calcium on these components are limited. OBJECTIVE: Our objective was to measure the initial mucosal uptake and the subsequent serosal transfer of nonheme iron and to determine the effects of adding calcium to a meal on both heme- and nonheme-iron retention. DESIGN: Whole-gut lavage and whole-body scintillation counting methods were applied to determine the 8-h uptake of nonheme iron and the 2-wk retention (absorption) of heme and nonheme iron in healthy adults (n = 17) after the consumption of meals of radiolabeled food. RESULTS: The initial uptake and absorption of nonheme iron were 11% and 7%, respectively, and the absorption of heme iron was 15%. Two-thirds of the nonheme iron taken up by the mucosa within 8 h was retained by the body after 2 wk (serosal transfer index: 0.63). Serum ferritin correlated inversely with the initial uptake and absorption of nonheme iron, but not with the nonheme serosal transfer index or the absorption of heme iron. Adding calcium (127 mg in cheese) to the meal did not affect absorption. CONCLUSIONS: On the basis of its association with serum ferritin, the initial mucosal uptake was the primary control point for nonheme-iron absorption. An apparent reduction in heme-iron absorption associated with the lavage procedure suggested that uptake of heme iron may take longer and proceed further through the intestine than that of nonheme iron. The absorption of both forms of iron was unaffected by the addition of cheese to this meal with high iron bioavailability.     

Dietary intake does not account for differences in low iron stores among Mexican American and non-Hispanic white women: Third National Health and Nutrition Examination Survey, 1988-1994

We used nationally representative data from the third National Health and Nutrition Examination Survey (NHANES III) to examine the relationship between low iron stores (serum ferritin < 12 microg/L) and dietary patterns that might affect iron status among Mexican American (MA) and non-Hispanic white (NHW) girls and women of reproductive age (12-39 y). Dietary data from the qualitative food-frequency questionnaire were used to classify subjects into three categories (using the 25th and 75th quartile values for NHW) for intake of heme iron, nonheme iron, iron absorption enhancers, and iron absorption inhibitors. The prevalence of low iron stores was 17.4% among MA (n = 1368) and 7.9% among NHW (n = 1473). Compared with high intake, the adjusted odds ratio (OR) for low iron stores was 1.80 [95% confidence interval (CI), 1.24-2.62] for medium intake of heme iron and 0.48 (95% CI, 0.25-0.91) for low intake of nonheme iron (plus iron supplement). Compared with no use, use of vitamin C supplements was associated with half the risk of low iron stores (OR = 0.50; 95% CI, 0.29-0.87). Similar results were found after income and parity were controlled for, except that the protective effect of vitamin C supplements was no longer significant. Even after adjustment for sociodemographic and dietary factors, MA women remained at increased risk for low iron stores (OR = 1.80; 95% CI, 1.30-2.49) indicating that the reasons for the higher prevalence of iron deficiency in MA women warrants further investigation.     

Ascorbic acid from lime juice does not improve the iron status of iron-deficient women in rural Mexico

BACKGROUND: Although ascorbic acid (AA) increases dietary iron bioavailability, there has been no food-based community trial of its efficacy in improving iron status. OBJECTIVE: The objective was to assess the efficacy of 25 mg AA as agua de limón (limeade), consumed with each of 2 daily meals, in improving the iron status of iron-deficient women. DESIGN: Two rural Mexican populations were randomly assigned to an AA or a placebo group, each with 18 iron-deficient women. The AA group was given 500 mL limeade containing 25 mg AA twice a day, 6 d/wk, for 8 mo. The placebo group was given a lime-flavored beverage free of AA or citric acid. Beverages were consumed within 30 min of 2 main daily meals. Data were collected on morbidity (3 times/wk), dietary intake (on 6 d), socioeconomic status, parasites (twice), medical history, and response to treatment. Blood samples at 0, 2, 4, 6, and 8 mo were analyzed for hemoglobin, plasma AA, plasma ferritin, transferrin receptors, and C-reactive protein. RESULTS: AA intake was significantly (P < 0.0001) higher in the AA group, but nonheme iron, heme iron, and phytic acid intakes did not differ significantly. Plasma AA was significantly (P < 0.01) higher in the AA group at 2, 4, 6, and 8 mo. There were no final differences between groups in hemoglobin, plasma ferritin, or transferrin receptor concentrations or in the ratio of transferrin receptors to plasma ferritin after control for initial concentrations. CONCLUSION: Increasing dietary AA by 25 mg at each of 2 meals/d did not improve iron status in iron-deficient women consuming diets high in phytate and nonheme iron.