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Biomedical subjects

Richard F Hurrell

Publications and source records attributed to Richard F Hurrell.

At least 19 recordsLinked to original sources

Iron bioavailability: UK Food Standards Agency workshop report.

The UK Food Standards Agency convened a group of expert scientists to review current research investigating factors affecting iron status and the bioavailability of dietary iron. Results presented at the workshop show menstrual blood loss to be the major determinant of body iron stores in premenopausal women. In the presence of abundant and varied food supplies, the health consequences of lower iron bioavailability are unclear and require further investigation.

Biological Availability↗

Effect of concurrent vitamin A and iodine deficiencies on the thyroid-pituitary axis in rats.

OBJECTIVE: Deficiencies of vitamin A and iodine are common in many developing countries. Vitamin A deficiency (VAD) may adversely affect thyroid metabolism. The study aim was to investigate the effects of concurrent vitamin A and iodine deficiencies on the thyroid-pituitary axis in rats. DESIGN: Weanling rats (n = 56) were fed diets deficient in vitamin A (VAD group), iodine (ID group), vitamin A and iodine (VAD + ID group), or sufficient in both vitamin A and iodine (control) for 30 days in a pair-fed design. Serum retinol (SR), thyroid hormones (FT(4), TT(4), FT(3), and TT(3)), serum thyrotropin (TSH), pituitary TSHbeta mRNA expression levels, and thyroid weights were determined at the end of the depletion period. MAIN OUTCOME: Compared to the control and ID groups, SR concentrations were about 35% lower in the VAD and VAD + ID groups (p < 0.001), indicating moderate VA deficiency. Comparing the VAD and control groups, there were no significant differences in TSH, TSHbeta mRNA, thyroid weight, or thyroid hormone levels. Compared to the control group, serum TSH, TSHbeta mRNA, and thyroid weight were higher (p < 0.05), and FT4 and TT4 were lower (p < 0.001), in the VAD + ID and ID groups. Compared to the ID group, TSH, TSHbeta mRNA, and thyroid weight were higher (p < 0.01) and FT(4) and TT(4) were lower (p < 0.001) in the VAD + ID group. There were no significant differences in TT3 or FT3 concentrations among groups. CONCLUSION: Moderate VAD alone has no measurable effect on the pituitary-thyroid axis. Concurrent ID and VAD produce more severe primary hypothyroidism than ID alone.

Animals↗

Iron status and food matrix strongly affect the relative bioavailability of ferric pyrophosphate in humans.

BACKGROUND: Although ferric pyrophosphate is a promising compound for iron fortification of foods, few data are available on the effect of food matrices, processing, and ascorbic acid on its bioavailability. OBJECTIVE: We compared the relative bioavailability (RBV) of ferrous sulfate in an experimental form of micronized dispersible ferric pyrophosphate (MDFP) in a wheat-milk infant cereal given with and without ascorbic acid with the RBV of MDFP from a processed and unprocessed rice meal. DESIGN: A crossover design was used to measure iron absorption in young women (n = 26) from test meals fortified with isotopically labeled [57Fe]-MDFP and [58Fe]-ferrous sulfate, based on erythrocyte incorporation of stable isotope labels 14 d later. RESULTS: Geometric mean iron absorption from the wheat-based meal fortified with MDFP was 2.0% and that from the meal fortified with ferrous sulfate was 3.2% (RBV = 62). The addition of ascorbic acid at a molar ratio of 4:1 to iron increased iron absorption from MDFP to 5.8% and that from ferrous sulfate to 14.8% (RBV = 39). In the rice meals, mean iron absorption from MDFP added to the rice at the time of feeding was 1.7%, and that from ferrous sulfate was 11.6% (RBV = 15). The mean iron absorption from MDFP extruded into artificial rice grains was 3.0% and that from ferrous sulfate in unprocessed rice was 12.6% (RBV = 24). Sixteen of 26 subjects were iron deficient. Iron status was a highly significant predictor of the RBV of MDFP (P < 0.001). CONCLUSION: RBV of the experimental MDFP varied markedly with food matrix and iron status. Assigning a single RBV value to poorly soluble compounds may be of limited value in evaluating their suitability for food fortification.

Absorption↗

Vitamin A supplementation in children with poor vitamin A and iron status increases erythropoietin and hemoglobin concentrations without changing total body iron.

BACKGROUND: Vitamin A deficiency impairs iron metabolism; vitamin A supplementation of vitamin A-deficient populations may reduce anemia. The mechanism of these effects is unclear. In vitro and in animal models, vitamin A treatment increases the production of erythropoietin (EPO), a stimulant of erythropoiesis. OBJECTIVE: We measured the effect of vitamin A supplementation on hemoglobin, iron status, and circulating EPO concentrations in children with poor iron and vitamin A status. DESIGN: In a double-blind, randomized trial, Moroccan schoolchildren (n = 81) were given either vitamin A (200,000 IU) or placebo at baseline and at 5 mo. At baseline, 5 mo, and 10 mo, hemoglobin, indicators of iron and vitamin A status, and EPO were measured. RESULTS: At baseline, 54% of children were anemic; 77% had low vitamin A status. In the vitamin A group at 10 mo, serum retinol improved significantly compared with the control group (P < 0.02). Vitamin A treatment increased mean hemoglobin by 7 g/L (P < 0.02) and reduced the prevalence of anemia from 54% to 38% (P < 0.01). Vitamin A treatment increased mean corpuscular volume (P < 0.001) and decreased serum transferrin receptor (P < 0.001), indicating improved iron-deficient erythropoiesis. Vitamin A decreased serum ferritin (P < 0.02), suggesting mobilization of hepatic iron stores. Calculated from the ratio of transferrin receptor to serum ferritin, overall body iron stores remained unchanged. In the vitamin A group at 10 mo, we observed an increase in EPO (P < 0.05) and a decrease in the slope of the regression line of log10(EPO) on hemoglobin (P < 0.01). CONCLUSION: In children deficient in vitamin A and iron, vitamin A supplementation mobilizes iron from existing stores to support increased erythropoiesis, an effect likely mediated by increases in circulating EPO.

Adolescent↗

Extruded rice fortified with micronized ground ferric pyrophosphate reduces iron deficiency in Indian schoolchildren: a double-blind randomized controlled trial.

BACKGROUND: Iron fortification of rice could be an effective strategy for reducing iron deficiency anemia in South Asia. OBJECTIVE: We aimed to determine whether extruded rice grains fortified with micronized ground ferric pyrophosphate (MGFP) would increase body iron stores in children. DESIGN: In a double-blind, 7-mo, school-based feeding trial in Bangalore, India, iron-depleted, 6-13-y-old children (n = 184) were randomly assigned to receive either a rice-based lunch meal fortified with 20 mg Fe as MGFP or an identical but unfortified control meal. The meals were consumed under direct supervision, and daily leftovers were weighed. All children were dewormed at baseline and at 3.5 mo. Iron status and hemoglobin were measured at baseline, 3.5 mo, and 7 mo. RESULTS: At baseline, the prevalences of iron deficiency and iron deficiency anemia in the total sample were 78% and 29%, respectively. After 7 mo of feeding, there was a significant increase in body iron stores in both study groups (P < 0.001), with a greater increase in the iron group than in the control group (P < 0.05). There was a significant time x treatment interaction for iron deficiency, which fell from 78% to 25% in the dewormed iron group and from 79% to 49% in the dewormed control group. Iron deficiency anemia decreased from 30% to 15% (NS) in the iron group but remained virtually unchanged in the control group (28% and 27%). In sensory tests, the MGFP-fortified rice (fortified at 3 and 5 mg Fe/100 g) was indistinguishable from natural rice, in both cooked and uncooked form. CONCLUSIONS: Extruded rice fortified with MGFP has excellent sensory characteristics. Fed in a school lunch meal, it increases iron stores and reduces the prevalence of iron deficiency in Indian children.

Adolescent↗

Meat protein fractions enhance nonheme iron absorption in humans.

The nature of the enhancing effect of muscle tissue on nonheme iron absorption in humans is unclear but thought to be related to muscle proteins. We conducted radioiron absorption studies to compare iron absorption from proteins isolated from beef and chicken muscle with that from freeze-dried beef and chicken muscle and from egg albumin. All meals contained an equivalent amount of protein as part of a semisynthetic liquid formula. Freeze-dried beef and chicken muscle increased iron absorption 180% (P < 0.001) and 100% (P < 0.001), respectively, relative to egg albumin. When added to the meal at an equivalent protein level (15 g), the isolated beef protein and the isolated heme-free beef protein with 94 and 98% protein content, respectively, increased iron absorption to the same extent as the native beef muscle. Similarly, when added to the meal at an equivalent protein level (30 g), isolated chicken muscle protein (94% protein) increased iron absorption similarly to native chicken muscle. Iron absorption from the meal containing the isolated heme-free chicken protein, however, was 120% (P < 0.01) greater than from the meal containing freeze-dried chicken muscle, indicating that a nonprotein component of muscle tissue with iron-binding potential may have been removed or concentrated by the protein extraction and separation procedures. Our results support the hypothesis that the enhancing effect of muscle tissue on iron absorption is mainly protein related but indicate that other factors may also play a role.

Absorption↗

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.

Adult↗

Salt dual-fortified with iodine and micronized ground ferric pyrophosphate affects iron status but not hemoglobin in children in Cote d'Ivoire.

Deficiencies of iron and iodine are common in West Africa, and salt is one of very few food vehicles available for fortification. Salt dual-fortified with iodine and micronized ground ferric pyrophosphate (FePP) was tested for its efficacy in rural, tropical Côte d'Ivoire. First, salt and iron intakes, and iron bioavailability were estimated using 3-d weighed food records in 24 households. Local iodized salt was then fortified with 3 mg Fe/g salt as ground FePP (mean particle size = 2.5 mum), and stability, sensory and acceptability trials were done. The dual fortified salt (DFS) was distributed to households and its efficacy compared with that of iodized salt (IS) in a 6-mo, double-blind trial in 5- to 15-y-old iron-deficient children (n = 123). All children were dewormed at baseline. After 6 mo, serum ferritin (SF) and transferrin receptor (TfR) concentrations as well as body iron stores improved significantly in the DFS group but not in the IS GROUP (P < 0.05). Body iron increased from 4.6 +/- 2.7 to 5.9 +/- 2.7 mg/kg (mean +/- SD) in the DFS group; concentrations before and after treatment in the IS group were 5.5 +/- 2.9 and 5.6 +/- 3.1 mg/kg, respectively. The hemoglobin concentration and the prevalence of anemia did not change in either group. The prevalences of malaria, soil-transmitted helminths, and riboflavin deficiency were 55, 14, and 66%, respectively. In tropical West Africa, low-grade salt fortified with micronized ground FePP increased body iron stores but not hemoglobin in children. Iron utilization may have been impaired by the high prevalence of malaria and concurrent nutrient deficiencies.

Adolescent↗

Iron fortification reduces blood lead levels in children in Bangalore, India.

OBJECTIVE: Chronic lead poisoning and iron deficiency are concentrated in urban children from lower socioeconomic strata, and both impair neurocognitive development. Our study objective was to determine if iron fortification reduces blood lead levels in urban, lead-exposed, iron-deficient children in Bangalore, India. DESIGN, SETTING, AND PARTICIPANTS: A randomized, double-blind, controlled school-based feeding trial was done in 5- to 13-year-old iron-deficient children (n = 186). At baseline, a high prevalence of lead poisoning was found in the younger children. Subsequently, all 5- to 9-year-old children participating in the trial (n = 134) were followed to determine if iron fortification would affect their blood lead levels. INTERVENTION: Children were dewormed and fed 6 days/week for 16 weeks either an iron-fortified rice meal (approximately 15 mg of iron per day as ferric pyrophosphate) or an identical control meal without added iron. Feeding was directly supervised and compliance monitored. OUTCOME MEASURES: Hemoglobin, serum ferritin, C-reactive protein, transferrin receptor, zinc protoporphyrin, and blood lead concentrations were measured. RESULTS: The prevalence of iron deficiency was significantly reduced in the iron group (from 70% to 28%) compared with the control group (76% to 55%). There was a significant decrease in median blood lead concentration in the iron group compared with the control group. The prevalence of blood lead levels > or =10 microg/dL was significantly reduced in the iron group (from 65% to 29%) compared with the control group (68% to 55%). CONCLUSIONS: Our findings suggest providing iron in a fortified food to lead-exposed children may reduce chronic lead intoxication. Iron fortification may be an effective and sustainable strategy to accompany environmental lead abatement.

Adolescent↗

Comparison of manual and automated ELISA methods for serum ferritin analysis.

Serum ferritin concentration is a sensitive measure of body iron stores. The aim of this study was to compare the performance of two commercially available enzyme-linked immunoassays (ELISAs) for serum ferritin: a widely used manual assay kit (Spectro Ferritin MT), and a new fully automated assay (Immulite). We analyzed serum samples from Moroccan school-aged children (n=51) from a rural area with a high prevalence of iron deficiency anemia (IDA). Four replicates of each sample were analyzed using both assays. For the manual method, the interassay repeatability was 24%, 22%, and 11%, and intraassay precision was 18.3%, 9.2%, and 9.1% at increasing serum ferritin concentrations. Using the automated assay, the interassay repeatability was 7%, 6%, and 6%, and intraassay precision was 1.5%, 5.4%, and 5.5% at increasing serum ferritin concentrations. The two assays were well correlated (y=1.16x+1.83; r=0.98). However, the limits of agreement (LOAs) were wide, particularly at low concentrations. A comparison of the assay results with recommended cutoffs for serum ferritin generated sharply different estimates of the prevalence of iron deficiency (ID) in the sample. We conclude that the automated assay has several potential advantages compared to the manual method, including better precision, less operator dependence, and faster sample through-put.

Adolescent↗

Iron deficiency due to consumption of a habitual diet low in bioavailable iron: a longitudinal cohort study in Moroccan children.

BACKGROUND: In many developing countries, cereal and legume-based diets contain low amounts of bioavailable iron, which may increase the risk of iron deficiency. OBJECTIVE: The objective was to measure change in iron status in Moroccan children who consumed their habitual diet containing low amounts of bioavailable iron. DESIGN: The design was a prospective, longitudinal, free-living cohort study in iron-replete, nonanemic 6-10-y-old children (n = 126). Hemoglobin, serum ferritin, and transferrin receptor were measured at baseline. The children then consumed their habitual cereal and legume-based diet for 15 mo, when their iron status was retested. We used weighed food records and direct food analysis to calculate dietary iron intake and iron bioavailability. On the basis of the change in hemoglobin and body iron stores calculated from the serum transferrin receptor-to-ferritin ratio, iron balance and iron absorption were estimated over the 15-mo period. RESULTS: Mean daily iron intake was 10.8 mg/d, 97% of which was nonheme iron. Estimated nonheme-iron bioavailability from algorithms was 1.0-4.3% adjusted for low body iron stores. Over 15 mo, the mean change in total body iron was -142 mg, and mean iron absorption was estimated to be 0.22 mg/d, or 2% of dietary iron. Mean hemoglobin concentration decreased 12 g/L. At 15 mo, 75% of the cohort had deficits in tissue iron, and one-third had mild iron deficiency anemia. CONCLUSION: Low iron bioavailability from legume and cereal-based diets is a cause of iron deficiency anemia in children in rural Africa.

Anemia, Iron-Deficiency↗

Serum transferrin receptor and zinc protoporphyrin as indicators of iron status in African children.

BACKGROUND: Although transferrin receptor (TfR) and zinc protoporphyrin (ZnPP) are often used to define iron status in school-age children in developing countries, the diagnostic cutoffs for this age group are uncertain. OBJECTIVE: The objective was to determine the sensitivity and specificity of TfR and ZnPP in predicting iron deficiency in black and white children in Africa. DESIGN: Hemoglobin, C-reactive protein (CRP), serum ferritin (SF), TfR, and ZnPP were measured in children in Côte d'Ivoire and Morocco. We excluded children with elevated CRP and then used receiver operating characteristic (ROC) curves to evaluate TfR and ZnPP alone and in combination in screening for iron deficiency, defined as an SF concentration <15 mug/L, and iron deficiency anemia (IDA), defined as an SF concentration <15 mug/L and low hemoglobin. RESULTS: The sample included 2814 children aged 5-15 y. The sensitivity and specificity of TfR and ZnPP were limited by considerable overlap between iron-sufficient, nonanemic children and those with IDA. On the basis of ROC curves, we identified diagnostic cutoffs for TfR and ZnPP that achieved specificities and sensitivities of approximately 60-80%. Separate cutoffs for Côte d'Ivoire and Morocco gave the best performance; the cutoffs for both TfR and ZnPP were higher in Côte d'Ivoire. Moreover, a comparison of nonanemic, iron-sufficient subjects showed that Ivorian children had significantly higher TfR and ZnPP concentrations than did Moroccan children (P < 0.01). CONCLUSIONS: New diagnostic cutoffs for TfR and ZnPP, based on ROC curve analyses, may improve the performance of these indexes in defining iron status in children. Significant ethnic differences in TfR and ZnPP suggest that separate cutoffs may be needed for black and white children.

Adolescent↗

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.

Adolescent↗

Effect of ascorbic acid and particle size on iron absorption from ferric pyrophosphate in adult women.

The effects of added ascorbic acid and particle size on iron absorption from ferric pyrophosphate were evaluated in adult women (9-10 women/study) based on erythrocyte incorporation of iron stable isotopes (57Fe or 58Fe) 14 days after administration. Three separate studies were made with test meals of iron-fortified infant cereal (5 mg iron/meal) and the results are presented as geometric means and relative bioavailability values (RBV, FeSO4 = 100%). The results of study 1 showed that iron absorption was significantly lower from ferric pyrophosphate (mean particle size 8.5 microm) than from FeSO4 in meals without ascorbic acid (0.9 vs. 2.6%, p < 0.0001, RBV 36%) and in the same meals with ascorbic acid added at a 4:1 molar ratio relative to fortification iron (2.3 vs. 9.7%, p < 0.0001, RBV 23%). Ascorbic acid increased iron absorption from ferric pyrophosphate slightly less (2.6-fold) than from FeSO4 (3.7-fold) (p < 0.05). In studies 2 and 3, RBV of ferric pyrophosphate with an average particle size of 6.7 microm and 12.5 pm was not significantly different at 52 and 42% (p > 0.05), respectively. In conclusion, the addition of ascorbic acid increased fractional iron absorption from ferric pyrophosphate significantly, but to a lesser extent than from FeSO4. Decreasing the mean particle size to 6.7 microm did not significantly increase iron absorption from ferric pyrophosphate.

Adult↗

Enhancing the absorption of fortification iron. A SUSTAIN Task Force report.

Iron deficiency remains a major global health problem affecting an estimated 2 billion people. The World Health Organization ranked it as the seventh most important preventable risk for disease, disability, and death in 2002. Since an important factor in its causation is the poor bioavailability of iron in the cereal-based diets of many developing countries, SUSTAIN set up a Task Force, consisting of nutritional, medical, industry, and government experts to consider strategies for enhancing the absorption of fortification iron. This paper summarizes the findings of this Task Force. Detailed reviews of each strategy follow this overview. Highly soluble compounds of iron like ferrous sulfate are desirable food fortificants but cannot be used in many food vehicles because of sensory issues. Thus, potentially less well-absorbed forms of iron commonly are used in food fortification. The bioavailability of iron fortificants can, however, be enhanced with innovative ingredient technologies. Ascorbic acid, NaFeEDTA, ferrous bisglycinate, and dephytinization all enhance the absorption of fortification iron, but add to the overall costs of fortification. While all strategies cannot be recommended for all food fortification vehicles, individual strategies can be recommended for specific foods. For example, the addition of ascorbic acid is appropriate for dry blended foods such as infant foods and other dry products made for reconstitution that are packaged, stored, and prepared in a way that maximizes retention of this vitamin. NaFeEDTA can be recommended for fortification of fish sauce and soy sauce, whereas amino acid chelates may be more useful in milk products and beverages. With further development, dephytinization may be possible for low-cost, cereal-based complementary foods in developing countries. Encapsulation of iron salts in lipid coatings, while not an iron absorption-enhancing strategy per se, can prevent soluble forms of iron from interacting undesirably with some food vehicles and hence broaden the application of some fortificants. Research relevant to each of these strategies for enhancing the bioavailability or utility of iron food fortificants is reviewed. Individual strategies are evaluated in terms of enhancing effect and stability, organoleptic qualities, cost, and regulatory issues of interest to the nutrition community, industry, and consumers. Recommendations are made on potential usages and further research needs. Effective fortification depends on the selection of technically feasible and efficacious strategies. Once suitable strategies have been identified, cost becomes very important in selecting the best approach to implement. However it is essential to calculate cost in relation to the amount of bioavailable iron delivered. An approach to the calculation of cost using a conservative estimate of the enhancing effects of the innovative technologies discussed in the supplement is given in the final section.

Absorption↗

Phytic acid degradation as a means of improving iron absorption.

Phytic acid is a potent inhibitor of native and fortification iron absorption and low absorption of iron from cereal- and/or legume-based complementary foods is a major factor in the etiology of iron deficiency in infants. Dephytinization of complementary foods or soy-based infant formulas is technically possible but, as phytic acid is strongly inhibitory at low concentrations, complete enzymatic degradation is recommended. If this is not possible, the phytic acid to iron molar ratio should be decreased to below 1:1 and preferably below 0.4:1. Complete dephytinization of cereal- and legume-based complementary foods has been shown to increase the percentage of iron absorption by as much as 12-fold (0.99% to 11.54%) in a single-meal study when the foods were reconstituted with water. The addition of milk, however, inhibits iron absorption and overcomes the enhancing effect of phytic acid degradation. Dephytinization can therefore be strongly recommended only for cereal/legume mixtures reconstituted with water, especially low-cost complementary foods destined for infants in developing countries. In countries where infant cereals are consumed with milk, ascorbic acid addition can more easily be used to overcome the negative effect of phytic acid on iron absorption. Similarly with soy-based infant formulas, especially if manufactured from low-phytate isolates, ascorbic acid can be used to ensure adequate iron absorption.

6-Phytase↗

Comparison of urinary monitoring, faecal monitoring and erythrocyte analysis of stable isotope labels to determine magnesium absorption in human subjects.

We have evaluated urinary monitoring and erythrocyte analysis to determine Mg absorption in human subjects as alternatives to the conventional technique of faecal monitoring by stable-isotope techniques. Ten healthy adults received 2.2 mmol (25)Mg in water, together with wheat bread, followed 15 min later by intravenous injection of 0.6 mmol (26)Mg (day 1). Brilliant blue and Yb (given on day 0 and day 1 respectively) served as qualitative and quantitative faecal markers. Urine was collected for 6 d after test meal intake. Complete collections of faeces were made until excretion of the second brilliant blue marker (given on day 7). Mg isotope ratios were determined by thermal ionisation-MS in urine and faeces and by inductively coupled plasma-MS in erythrocytes. Absorption was determined based on: (1) 6 d urine pools; (2) 24 h urine pools (collected 22-46 h after test meal intake); (3) erythrocytes from a blood sample drawn on day 14; (4) complete 6 d faecal pools; (5) faecal pools based on the first three consecutive stools after excretion of the first brilliant blue marker. Differences in mean Mg absorption (42 44 %) were statistically insignificant between techniques, except when based on 6 d urine pools for which the value was significantly lower (33 (sd 7) %, P=0.0003, ANOVA). The results indicate that Mg absorption can be determined from 24 h urine pools or erythrocytes obtained 14 d after test meal intake, an alternative method to the more time-consuming and labour-intense faecal monitoring. The choice of technique depends on practical and financial considerations.

Absorption↗