Zinc absorption in infants fed iron-fortified weaning food

The Molecular Basis for Zinc Bioavailability

Zinc is an essential micronutrient, and its deficiency is perhaps the most prevalent and least understood worldwide. Recent advances have expanded the understanding of zinc’s unique chemistry and molecular roles in a vast array of critical functions. However, beyond the concept of zinc absorption, few studies have explored the molecular basis of zinc bioavailability that determines the proportion of dietary zinc utilized in zinc-dependent processes in the body. The purpose of this review is to merge the concepts of zinc molecular biology and bioavailability with a focus on the molecular determinants of zinc luminal availability, absorption, transport, and utilization.

Toward revising dietary zinc recommendations for children aged 0 to 3 years: a systematic review and meta-analysis of zinc absorption, excretion, and requirements for growth

CONTEXT

The Food and Agriculture Organization of the United Nations and the World Health Organization are updating their dietary zinc recommendations for children aged 0 to 3 years.

OBJECTIVE

The aim of this review was to retrieve and synthesize evidence regarding zinc needs for growth as well as zinc losses, absorption, and bioavailability from the diet.

DATA SOURCES

MEDLINE, Embase, and Cochrane Library databases were searched electronically from inception to August 2020. Studies assessing the above factors in healthy children aged 0 to 9 years were included, with no limits on study design or language.

DATA EXTRACTION

Ninety-four studies reporting on zinc content in tissue (n = 27); zinc absorption (n = 47); factors affecting zinc bioavailability (n = 30); and endogenous zinc losses via urine, feces, or integument (n = 40) met the inclusion criteria. Four reviewers extracted data and two reviewers checked for accuracy.

DATA ANALYSES

Studies were synthesized narratively, and meta-analyses of zinc losses and gains as well the subgroups of age, type of feeding, country's income, and molar ratio of phytate to zinc were conducted. Meta-analysis revealed an overall mean (95%CI) urinary and endogenous fecal zinc excretion of 17.48 µg/kg/d (11.80-23.15; I2 = 94%) and 0.07 mg/kg/d (0.06-0.08; I2 = 82%), respectively, with a mean fractional zinc absorption of 26.75% (23.69-29.81; I2 = 99%). Subgrouping by age revealed differences in mean values associated with the transition from milk-based diets to solid food during the first 3 years of life.

CONCLUSION

This review synthesizes data that may be used to formulate zinc requirements in young children. Results should be interpreted with caution because of considerable heterogeneity in the evidence.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number CRD42020215236.

Differences in Micronutrient Intakes of Exclusive and Partially Breastfed Indonesian Infants from Resource-Poor Households are Not Accompanied by Differences in Micronutrient Status, Morbidity, or Growth

BACKGROUND

When maternal micronutrient intakes and statuses are compromised, reductions in micronutrient concentrations in neonatal stores and human milk may result in suboptimal micronutrient intakes, statuses, and functional outcomes of breastfed infants during the critical first 6-month period.

OBJECTIVES

We compared the adequacy of micronutrient intakes and statuses at 2 and/or 5 months and morbidity and growth faltering at 2, 5, and 12 months in a cohort of exclusively breastfed (EBF) and partially breastfed (PBF) infants from low-resource Indonesian households.

METHODS

At 2 and 5 months, the breastfeeding status and human milk intake of 212 infants were determined using the deuterium oxide dose-to-mother technique, and intakes were calculated from milk micronutrient concentrations and 3-d weighed food intakes. At 5 months, five infant micronutrient biomarkers, hemoglobin, C-reactive protein, and α-1-acid-glycoprotein were measured. Infant morbidity, weight, and length were measured at 2, 5, and 12 months. Means, medians, or proportions were reported for each group and differences between groups were statistically determined.

RESULTS

Median intakes of iron, thiamin, niacin, and vitamin B-12 were higher in PBF than EBF infants at 5 months (all P values < 0.05), but intakes in all infants were below adequate intakes. At 5 months, anemia was <20% in both groups, although fewer PBF versus EBF infants had vitamin B-12 deficiency (11.5% vs. 28.6%, respectively; P = 0.011). The mean ± SD length-for-age z-scores for EBF versus PBF infants at 2 months were 0.7 ± 0.9 versus -0.5 ± 1.1, respectively  (P = 0.158), declining to -1.4 ± 0.9 versus -1.1 ± 1.2, respectively, at 12 months (P = 0.059). Reported morbidity rates were generally low, with no evidence of a difference between infant groups (all P values > 0.126).

CONCLUSIONS

Irrespective of exclusive or partial breastfeeding status, micronutrient intakes of infants were low, statuses were compromised, and growth faltering during the critical 6 months period of early infancy was present. The findings highlight the importance of improving maternal nutritional statuses and evaluating their impacts on infant outcomes.

Interactions of iron with manganese, zinc, chromium, and selenium as related to prophylaxis and treatment of iron deficiency

Iron (Fe) deficiency is considered as the most common nutritional deficiency. Iron deficiency is usually associated with low Fe intake, blood loss, diseases, poor absorption, gastrointestinal parasites, or increased physiological demands as in pregnancy. Nutritional Fe deficiency is usually treated with Fe tablets, sometimes with Fe-containing multimineral tablets. Trace element interactions may have a significant impact on Fe status. Existing data demonstrate a tight interaction between manganese (Mn) and Fe, especially in Fe-deficient state. The influence of Mn on Fe homeostasis may be mediated through its influence on Fe absorption, circulating transporters like transferrin, and regulatory proteins. The existing data demonstrate that the influence of zinc (Zn) on Fe status may be related to their competition for metal transporters. Moreover, Zn may be involved in regulation of hepcidin production. At the same time, human data on the interplay between Fe and Zn especially in terms of Fe-deficiency and supplementation are contradictory, demonstrating both positive and negative influence of Zn on Fe status. Numerous data also demonstrate the possibility of competition between Fe and chromium (Cr) for transferrin binding. At the same time, human data on the interaction between these metals are contradictory. Therefore, while managing hypoferremia and Fe-deficiency anemia, it is recommended to assess the level of other trace elements in parallel with indices of Fe homeostasis. It is supposed that simultaneous correction of trace element status in Fe deficiency may help to decrease possible antagonistic or increase synergistic interactions.

Mode of oral iron administration and the amount of iron habitually consumed do not affect iron absorption, systemic iron utilisation or zinc absorption in iron-sufficient infants: a randomised trial

Different metabolic pathways of supplemental and fortification Fe, or inhibition of Zn absorption by Fe, may explain adverse effects of supplemental Fe in Fe-sufficient infants. We determined whether the mode of oral Fe administration or the amount habitually consumed affects Fe absorption and systemic Fe utilisation in infants, and assessed the effects of these interventions on Zn absorption, Fe and Zn status, and growth. Fe-sufficient 6-month-old infants (n 72) were randomly assigned to receive 6·6 mg Fe/d from a high-Fe formula, 1·3 mg Fe/d from a low-Fe formula or 6·6 mg Fe/d from Fe drops and a formula with no added Fe for 45 d. Fractional Fe absorption, Fe utilisation and fractional Zn absorption were measured with oral (57Fe and 67Zn) and intravenous (58Fe and 70Zn) isotopes. Fe and Zn status, infection and growth were measured. At 45 d, Hb was 6·3 g/l higher in the high-Fe formula group compared with the Fe drops group, whereas serum ferritin was 34 and 35 % higher, respectively, and serum transferrin 0·1 g/l lower in the high-Fe formula and Fe drops groups compared with the low-Fe formula group (all P<0·05). No intervention effects were observed on Fe absorption, Fe utilisation, Zn absorption, other Fe status indices, plasma Zn or growth. We concluded that neither supplemental or fortification Fe nor the amount of Fe habitually consumed altered Fe absorption, Fe utilisation, Zn absorption, Zn status or growth in Fe-sufficient infants. Consumption of low-Fe formula as the only source of Fe was insufficient to maintain Fe stores.

A Review of Dietary Zinc Recommendations

BACKGROUND

Large discrepancies exist among the dietary zinc recommendations set by expert groups.

OBJECTIVE

To describe the basis for the differences in the dietary zinc recommendations set by the World Health Organization, the US Institute of Medicine, the International Zinc Nutrition Consultative Group, and the European Food Safety Agency.

METHODS

We compared the sources of the data, the concepts, and methods used by the 4 expert groups to set the physiological requirements for absorbed zinc, the dietary zinc requirements (termed estimated and/or average requirements), recommended dietary allowances (or recommended nutrient intakes or population reference intakes), and tolerable upper intake levels for selected age, sex, and life-stage groups.

RESULTS

All 4 expert groups used the factorial approach to estimate the physiological requirements for zinc. These are based on the estimates of absorbed zinc required to offset all obligatory zinc losses plus any additional requirements for absorbed zinc for growth, pregnancy, or lactation. However, discrepancies exist in the reference body weights used, studies selected, approaches to estimate endogenous fecal zinc (EFZ) losses, the adjustments applied to derive dietary zinc requirements that take into account zinc bioavailability in the habitual diets, number of dietary zinc recommendations set, and the nomenclature used to describe them.

CONCLUSIONS

Estimates for the physiological and dietary requirements varied across the 4 expert groups. The European Food Safety Agency was the only expert group that set dietary zinc recommendations at 4 different levels of dietary phytate for adults (but not for children) and as of yet no tolerable upper intake level for any life-stage group.

Fractional Zinc Absorption for Men, Women, and Adolescents Is Overestimated in the Current Dietary Reference Intakes

BACKGROUND

The fractional zinc absorption values used in the current Dietary Reference Intakes (DRIs) for zinc were based on data from published studies. However, the inhibitory effect of phytate was underestimated because of the low phytate content of the diets in the studies used.

OBJECTIVE

The objective of this study was to estimate the fractional absorption of dietary zinc from the US diet by using 2 published algorithms.

METHODS

Nutrient intake data were obtained from the NHANES 2009-2010 and the corresponding Food Patterns Equivalents Database. Data were analyzed with the use of R software by taking into account the complex survey design. The International Zinc Nutrition Consultative Group (IZiNCG; Brown et al. Food Nutr Bull 2004;25:S99-203) and Miller et al. (Br J Nutr 2013;109:695-700) models were used to estimate zinc absorption.

RESULTS

Geometric means (95% CIs) of zinc absorption for all subjects were 30.1% (29.9%, 30.2%) or 31.3% (30.9%, 31.6%) with the use of the IZiNCG model and Miller et al. model, respectively. For men, women, and adolescents, absorption values obtained in this study with the use of the 2 models were 27.2%, 31.4%, and 30.1%, respectively, for the IZiNCG model and 28.0%, 33.0%, and 31.6%, respectively, for the Miller et al. model, compared with the 41%, 48%, and 40%, respectively, used in the current DRIs. For preadolescents, estimated absorption values (31.1% and 32.8% for the IZiNCG model and Miller et al. model, respectively) compare well with the conservative estimate of 30% used in the DRIs. When the new estimates of zinc absorption were applied to the current DRI values for men and women, the results suggest that the Estimated Average Requirement (EAR) and RDA for these groups need to be increased by nearly one-half of the current values in order to meet their requirements for absorbed zinc.

CONCLUSIONS

These data suggest that zinc absorption is overestimated for men, women, and adolescents in the current DRI. Upward adjustments of the DRI for these groups are recommended.

Zinc absorption from micronutrient powder is low but is not affected by iron in Kenyan infants

Interference with zinc absorption is a proposed explanation for adverse effects of supplemental iron in iron-replete children in malaria endemic settings. We examined the effects of iron in micronutrient powder (MNP) on zinc absorption after three months of home fortification with MNP in maize-based diets in rural Kenyan infants. In a double blind design, six-month-old, non-anemic infants were randomized to MNP containing 5 mg zinc, with or without 12.5 mg of iron (MNP + Fe and MNP − Fe, respectively); a control (C) group received placebo powder. After three months, duplicate diet collections and zinc stable isotopes were used to measure intake from MNP + non-breast milk foods and fractional absorption of zinc (FAZ) by dual isotope ratio method; total absorbed zinc (TAZ, mg/day) was calculated from intake × FAZ. Mean (SEM) TAZ was not different between MNP + Fe (n = 10) and MNP - Fe (n = 9) groups: 0.85 (0.22) and 0.72 (0.19), respectively, but both were higher than C (n = 9): 0.24 (0.03) (p = 0.04). Iron in MNP did not significantly alter zinc absorption, but despite intakes over double estimated dietary requirement, both MNP groups' mean TAZ barely approximated the physiologic requirement for age. Impaired zinc absorption may dictate need for higher zinc doses in vulnerable populations.

Mathematical model of zinc absorption: effects of dietary calcium, protein and iron on zinc absorption

A previously described mathematical model of Zn absorption as a function of total daily dietary Zn and phytate was fitted to data from studies in which dietary Ca, Fe and protein were also measured. An analysis of regression residuals indicated statistically significant positive relationships between the residuals and Ca, Fe and protein, suggesting that the presence of any of these dietary components enhances Zn absorption. Based on the hypotheses that (1) Ca and Fe both promote Zn absorption by binding with phytate and thereby making it unavailable for binding Zn and (2) protein enhances the availability of Zn for transporter binding, the model was modified to incorporate these effects. The new model of Zn absorption as a function of dietary Zn, phytate, Ca, Fe and protein was then fitted to the data. The proportion of variation in absorbed Zn explained by the new model was 0·88, an increase from 0·82 with the original model. A reduced version of the model without Fe produced an equally good fit to the data and an improved value for the model selection criterion, demonstrating that when dietary Ca and protein are controlled for, there is no evidence that dietary Fe influences Zn absorption. Regression residuals and testing with additional data supported the validity of the new model. It was concluded that dietary Ca and protein modestly enhanced Zn absorption and Fe had no statistically discernable effect. Furthermore, the model provides a meaningful foundation for efforts to model nutrient interactions in mineral absorption.

Effect of iron-fortified foods on hematologic and biological outcomes: systematic review of randomized controlled trials

BACKGROUND

The utility of iron fortification of food to improve iron deficiency, anemia, and biological outcomes is not proven unequivocally.

OBJECTIVES

The objectives were to evaluate 1) the effect of iron fortification on hemoglobin and serum ferritin and the prevalence of iron deficiency and anemia, 2) the possible predictors of a positive hemoglobin response, 3) the effect of iron fortification on zinc and iron status, and 4) the effect of iron-fortified foods on mental and motor development, anthropometric measures, and infections.

DESIGN

Randomized and pseudorandomized controlled trials that included food fortification or biofortification with iron were included.

RESULTS

Data from 60 trials showed that iron fortification of foods resulted in a significant increase in hemoglobin (0.42 g/dL; 95% CI: 0.28, 0.56; P < 0.001) and serum ferritin (1.36 μg/L; 95% CI: 1.23, 1.52; P < 0.001), a reduced risk of anemia (RR: 0.59; 95% CI: 0.48, 0.71; P < 0.001) and iron deficiency (RR: 0.48; 95% CI: 0.38, 0.62; P < 0.001), improvement in other indicators of iron nutriture, and no effect on serum zinc concentrations, infections, physical growth, and mental and motor development. Significant heterogeneity was observed for most of the evaluated outcomes. Sensitivity analyses and meta-regression for hemoglobin suggested a higher response with lower trial quality (suboptimal allocation concealment and blinding), use of condiments, and sodium iron edetate and a lower response when adults were included.

CONCLUSION

Consumption of iron-fortified foods results in an improvement in hemoglobin, serum ferritin, and iron nutriture and a reduced risk of remaining anemic and iron deficient.

Plasma zinc concentration responds to short-term zinc supplementation, but not zinc fortification, in young children in Senegal1,2

BACKGROUND

Simple, low-cost methods are needed to evaluate the effect of zinc-fortification programs. Plasma zinc concentration is a useful biomarker of zinc intake from supplementation, but responses to zinc fortification are inconsistent.

OBJECTIVE

The objective was to compare the change in plasma zinc concentrations in young children who received zinc from either a liquid supplement or a zinc-fortified complementary food.

DESIGN

A double-blind intervention trial was conducted in 137 young Senegalese children aged 9-17 mo who were randomly assigned to receive one of the following treatments for 15 d: 1) 30 g dry weight of an iron-fortified cereal porridge and a liquid multivitamin supplement without zinc (control group), 2) the same porridge and multivitamin supplement with 6 mg Zn added to the supplement dose (ZnSuppl group), or 3) the same porridge with added zinc to provide 6 mg Zn per 25 g dry weight of porridge and multivitamin without zinc (ZnFort group).

RESULTS

Mean (±SD) plasma zinc concentration (μg/dL) increased by 4.7 ± 1.6 (P = 0.004) in the ZnSuppl group, which was significantly greater (P = 0.009) than the mean change in the control group (-1.0 ± 1.6; P = 0.51) and in the ZnFort group (-1.8 ± 1.7; P = 0.29). The latter 2 groups did not differ from each other (P = 0.99).

CONCLUSIONS

Plasma zinc concentration increased in children who received daily zinc supplementation for 15 d but not in those who received a zinc-fortified complementary food containing a similar amount of zinc. Additional longer-term studies are needed to assess the effect of zinc-fortification programs on zinc-related functional outcomes and the usefulness of plasma zinc as a biomarker of program effect. This trial was registered at www.clinicaltrials.gov as study NCT0094398.

Mineral homeostasis in young children consuming typical U.S. diets

Mineral requirements in young children are poorly understood, and current recommendations rely heavily on data collected in older children or adults. Our objectives were to assess the relationship between mineral (Ca, Mg, Fe, Zn, and Cu) intake in young U.S. children, and mineral absorption, excretion, and retention; and to use these data to re-examine the most recent recommended intakes. Thirty children, 1–4 y old, were studied on their usual diet. After 7 d of home adaptation they were admitted for either a 2-d or 5-d metabolic study where multiple stable isotope or Ca, Mg, Fe, Zn, and Cu were administered and mineral absorption (2-d study), or absorption and excretion (5-d study) were assessed. Fractional (%) absorption of some (Ca, Mg) but not all (Fe, Zn) minerals decreased as intake increased. Absolute (total) absorption and net retention of all the minerals increased as their intake increased. Mineral homeostasis was related to changes in fractional absorption (Ca and Mg), fecal excretion (Zn), or whole body mineral status (Fe). Our results support the current U.S. recommended intakes for 1–4-y-old children for Mg and Fe, but suggest that those for Ca and Zn are too low.

Influence of exogenous iron, calcium, protein and common salt on the bioaccessibility of zinc from cereals and legumes

We have earlier reported the zinc bioaccessibility from cereals and pulses and documented the influence of heat processing, germination and fermentation on the same. In the present study, we have assessed the influence of exogenous iron and calcium equivalent to their supplemental levels on the bioaccessibility of zinc from food grains that generally are the major components of meal in India. Bioaccessibility measurement was made by a procedure involving equilibrium dialysis during simulated gastrointestinal digestion. Exogenous iron equivalent to therapeutic levels (5mg per 10g of cereal-legume combination) significantly reduced the bioaccessibility of zinc from the food grains tested, the percent reduction being 32.4. Exogenous calcium equivalent to therapeutic levels (83mg per 10g of the cereal-legume combination) also significantly reduced (by 27.4%) the bioaccessibility of zinc from the tested food grains. The negative influence of exogenous iron and calcium was similar in both raw and cooked grains. Such negative influences on the bioaccessibility of zinc were however not seen when exogenous iron and calcium were only moderate (up to four times the intrinsic level). A study of the influence of exogenous protein on the bioaccessibility of zinc from food grains revealed that soy protein isolate added at amounts to result in a total protein content of 20% produced contrasting effects on zinc and iron bioaccessibility from cereals - rice and sorghum. While soy protein had a negative effect on iron bioaccessibility from these food grains, the same produced an enhancing effect on zinc bioaccessibility (an increase of 50% and 90% increase) from raw and cooked grain, respectively). Exogenous sodium chloride (at 5% level) potentiated the positive effect of soy protein on zinc bioaccessibility, and effectively countered its negative effect on iron bioaccessibility. The observed negative influence of supplemental iron and calcium on zinc bioaccessibility suggests that zinc supplementation may be necessary in the Indian context, whenever iron and calcium supplements are taken, to compensate for the reduction in zinc bioaccessibility.

Iron metabolism in infants and children

Meeting the iron requirements of infants and children is difficult, and supplementation or fortification of food with iron is often recommended. Although iron supplementation of infants and children with iron deficiency and iron-deficiency anemia may be beneficial, recent studies suggest that this may not be the case for those with adequate iron status, and adverse effects have been noted. The recent discoveries of proteins and peptides regulating iron absorption have enhanced our knowledge of iron metabolism in infants and children. Iron is taken up in the small intestine by divalent metal transporter-1 and is either stored by ferritin inside the mucosal cell or transported to the systemic circulation by ferroportin, while being oxidized by hephaestin to be incorporated into transferrin. Hepcidin, a small peptide synthesized by the liver, can sense iron stores and regulates iron transport by inhibition of ferroportin. However, regulation of iron transporters is immature in infants, possibly explaining the adverse effects of iron supplementation. Interactions among iron, vitamin A, zinc, and copper need to be considered when evaluating the effects of iron supplementation on infants and children.

Dietary indicators for assessing the adequacy of population zinc intakes

The assessment of dietary zinc intakes is an important component of evaluating the risk of zinc deficiency in populations, and for designing appropriate food-based interventions, including fortification, to improve zinc intakes. The prevalence of inadequate zinc intakes can describe the relative magnitude of the risk of zinc deficiency in the population and identify subpopulations at elevated risk. As a cornerstone to evaluating the adequacy of population zinc intakes globally, a set of internationally appropriate dietary reference intakes must be defined. The World Health Organization/Food and Agriculture Organization/International Atomic Energy Agency (WHO/FAO/IAEA) and the Food and Nutrition Board/US Institute of Medicine (FNB/IOM) have presented estimated average requirements (EAR) for dietary zinc intake, and, more recently, the International Zinc Nutrition Consultative Group (IZiNCG) presented a revised set of recommendations for international use. A prevalence of inadequate zinc intakes greater than 25% is considered to represent an elevated risk of population zinc deficiency. As the requirement estimates are derived from smaller, clinical studies and, for children, most components of the estimates are extrapolated from data for adults, it was desirable to evaluate their internal validity. The estimated physiological requirements for adult men and women appear to adequately predict zinc status as determined by biochemical indicators of status and/or zinc balance. With the use of data from available studies, the reported prevalence of low serum zinc concentration and the estimated prevalence of inadequate zinc intakes predict similar levels of risk of zinc deficiency, particularly among pregnant and nonpregnant women. Conformity between these two indicators is less consistent for children, suggesting that further data and/or direct studies of zinc requirements among children are needed.

Improved iron bioavailability in an oat-based beverage: the combined effect of citric acid addition, dephytinization and iron supplementation

BACKGROUND

Iron deficiency in children is a major worldwide nutritional problem. An oat beverage was developed for 1- to 3-year-old children and different treatments were used to improve the iron bioavailability.

AIM OF THE STUDY

To investigate the effects of citric acid addition, phytase treatment and supplementation with different iron compounds on non-heme iron absorption in human from a mineral-supplemented oat-based beverage.

METHODS

A 240 g portion of a 55Fe-labeled test product (T) or a 59Fe-labeled reference dose (R) was served as breakfast after overnight fasting on four consecutive days in the order of TRRT. On day 18 the retention of 59Fe was measured by a whole-body counter and the erythrocytes uptake of 55Fe and 59Fe by a liquid-scintillation counter. Forty-two healthy subjects (men and women) were randomized into four study groups, members of each being given one of the studied four products (A, B, C, and D) supplemented with Fe (1.3 mg/portion), Zn, Ca, Se and P. Ferric ammonium citrate (FeAC) was added to products A, B, and C and ferric pyrophosphate (FePP) to product D. Citric acid (60 mg/portion) was added to products B, C, and D and phytase treatment applied to products C and D.

RESULTS

Citric acid improved iron absorption by 54% from 3.9% in product A to 6.0% in product B (p = 0.051). Phytase treatment increased iron absorption by 78% (from 6.0 to 10.7%, p = 0.003) by reducing the phytate-phosphorus content per portion from 16.3 mg in product B to 2.8 mg in product C. The two compounds gave similar iron absorption rates (p = 0.916).

CONCLUSIONS

A combination of citric acid addition, dephytinization and iron supplementation significantly increased the iron absorption in an oat-based beverage. Such a beverage can be useful in the prevention of iron deficiency in 1- to 3-year-old children.

Adding zinc to supplemental iron and folic acid does not affect mortality and severe morbidity in young children

Studies have found a substantial reduction in diarrhea and respiratory morbidity in young children receiving zinc supplementation. The impact of daily zinc supplementation administered with iron plus folic acid (IFA) in young children on all-cause hospitalizations and mortality in comparison with IFA alone was evaluated. In a double blind cluster-randomized controlled trial, 94,359 subjects aged 1-23 mo were administered a daily dose of zinc plus IFA or IFA alone for a duration of 12 mo after enrollment. The intervention group tablet contained 10 mg of elemental zinc, 12.5 mg of iron, and 50 microg of folic acid. The control group tablets were similar except that they contained a placebo for zinc. Infants aged <6 mo were administered half a tablet, and those older received 1 tablet dissolved in breast milk or water. Hospitalizations were captured by trained study physicians through the surveillance of 8 hospitals. Deaths and hospitalizations were ascertained through visits to households by study supervisors once every 2 mo. The overall death rates did not differ significantly between the 2 groups when adjusted for cluster randomization (hazard ratio = 1.02, 95% CI 0.87, 1.19). Zinc and IFA supplementation compared with IFA alone did not affect adjusted hospitalization rates (overall rate ratio = 1.08, 95% CI 0.98, 1.19; diarrhea-specific rate ratio = 1.15, 95% CI 0.99, 1.34; or pneumonia-specific rate ratio = 1.09, 95% CI 0.94, 1.25). The lack of impact of zinc on mortality and hospitalization rates in this study may have been due to the use of lower daily zinc dosing than used in some of the morbidity prevention trials or from an interaction between zinc and iron, where the addition of iron may have adversely affected potential effects of zinc on immune function and morbidity. Future research should address iron and zinc interaction effects on important functional outcomes.

Demonstrating zinc and iron bioavailability from intrinsically labeled microencapsulated ferrous fumarate and zinc gluconate Sprinkles in young children

Nutrient-nutrient interactions are an important consideration for any multiple-micronutrient formulation, including Sprinkles, a home-fortification strategy to control anemia. The objectives of this randomized controlled trial were as follows: 1) to compare the absorption of zinc at 2 doses given as Sprinkles; and 2) to examine the effect of zinc and ascorbic acid (AA) on iron absorption from Sprinkles. Seventy-five children aged 12-24 mo were randomly assigned to the following groups: 1) 5 mg of labeled zinc (67Zn) with 50 mg AA (LoZn group); b) 10 mg of labeled zinc (67Zn) with 50 mg AA (HiZn group); or 3) 5 mg zinc with no AA (control). All groups contained 30 mg of labeled iron (57Fe). Intravenous infusions labeled with 70Zn (LoZn and HiZn groups) and 58Fe (control) were administered. Blood was drawn at baseline, 48 h and 14 d later. The percentage of zinc absorbed did not differ between LoZn (geometric mean = 6.4%; min-max: 1.7-14.6) and HiZn (geometric mean = 7.5%; min-max: 3.3-18.0) groups. However, total zinc absorbed was significantly different between the LoZn (geometric mean = 0.31 mg; min-max: 0.08-0.73) and HiZn (geometric mean = 0.82 mg; min-max: 0.33-1.82) groups (P = 0.0004). Geometric mean percentage iron absorption values did not differ between the LoZn (5.9%; min-max: 0.8-21) and HiZn (4.4%; min-max: 0.6-12.3) groups and between the LoZn and control groups (5.0%; min-max: 1.4-24). We conclude that zinc in the form of Sprinkles has a low bioavailability, yet provides adequate amounts of absorbed zinc in young children, and that there is no effect of zinc or AA on iron absorption from the given formulations of Sprinkles.

Na2EDTA enhances the absorption of iron and zinc from fortified rice flour in Sri Lankan children

Rice flour was proposed as a vehicle for iron and zinc fortification in Sri Lanka. Although widely consumed, rice flour has not been evaluated as a fortified food, and the absorption of minerals including iron and zinc from this flour is unknown. Determination of the bioavailability of these nutrients is a critical step before commencing a fortification program. We randomly divided 53 Sri Lankan schoolchildren ages 6-10 y into 4 groups that consumed a local dish prepared with 25 g of fortified rice flour labeled with one of the following: 1) (58)FeSO(4) 2) (58)FeSO(4) + Na(2)EDTA 3) (58)FeSO(4) + (67)ZnO or, 4) (58)FeSO(4) + Na(2)EDTA + (67)ZnO. The levels of iron and zinc were 60 mg/kg; the rice flour also contained folate at 2 mg/kg in each group. Na(2)EDTA was added at a Fe:Na(2)EDTA, 1:1 molar ratio. A total of 48 children completed the trial. Absorption of (58)Fe from a meal was significantly greater (P < 0.01) in the groups administered FeSO(4) + Na(2)EDTA (4.7 +/- 3.6%) than in those administered FeSO(4) without Na(2)EDTA (2.2 +/- 1.3%). Fractional absorption of zinc was 13.5 +/- 6.0% in the FeSO(4) + Na(2)EDTA group and 8.8 +/- 2.0% in the FeSO(4) group (P = 0.037). Although zinc absorption was low, our results demonstrated a benefit in using Na(2)EDTA to improve both iron and zinc absorption. We conclude that the fortification of rice flour is feasible, although additional strategies such as dephytinization or an increase in the level of iron and zinc fortification should be considered to obtain a higher proportion of the daily requirement of total absorbed iron and zinc.

A community-based randomized controlled trial of iron and zinc supplementation in Indonesian infants: effects on growth and development

BACKGROUND

Deficiencies of iron and zinc are associated with delayed development, growth faltering, and increased infectious-disease morbidity during infancy and childhood. Combined iron and zinc supplementation may therefore be a logical preventive strategy.

OBJECTIVE

The objective of the study was to compare the effects of combined iron and zinc supplementation in infancy with the effects of iron and zinc as single micronutrients on growth, psychomotor development, and incidence of infectious disease.

DESIGN

Indonesian infants (n = 680) were randomly assigned to daily supplementation with 10 mg Fe (Fe group), 10 mg Zn (Zn group), 10 mg Fe and 10 mg Zn (Fe+Zn group), or placebo from 6 to 12 mo of age. Anthropometric indexes, developmental indexes (Bayley Scales of Infant Development; BSID), and morbidity were recorded.

RESULTS

At 12 mo, two-factor analysis of variance showed a significant interaction between iron and zinc for weight-for-age z score, knee-heel length, and BSID psychomotor development. Weight-for-age z score was higher in the Zn group than in the placebo and Fe+Zn groups, knee-heel length was higher in the Zn and Fe groups than in the placebo group, and the BSID psychomotor development index was higher in the Fe group than in the placebo group. No significant effect on morbidity was found.

CONCLUSIONS

Single supplementation with zinc significantly improved growth, and single supplementation with iron significantly improved growth and psychomotor development, but combined supplementation with iron and zinc had no significant effect on growth or development. Combined, simultaneous supplementation with iron and zinc to infants cannot be routinely recommended at the iron-to-zinc ratio used in this study.

Processed complementary food does not improve growth or hemoglobin status of rural tanzanian infants from 6-12 months of age in Kilosa district, Tanzania

A double-blind, randomized, placebo-controlled trial was conducted from March 2001 to March 2002 involving 309 infants who received either a processed complementary food (CF) or an unprocessed placebo from 6 to 12 mo of age. The groups were comparable in baseline characteristics. The study took place in Kilosa district, Tanzania. The processed CF contained germinated, autoclaved, and dried finger millet (65.2%), kidney beans (19.1%), roasted-peanuts (8%), and mango purée (7.7%). The same blend, but not processed, served as the placebo. Processing increased iron solubility and energy density without affecting viscosity. Mean length for age, weight for age, hemoglobin, and zinc protoporphyrin at 6 and 12 mo did not differ between the 2 groups. The results show that the processed food did not differ from the unprocessed placebo in improving growth, hemoglobin, and iron status of infants when given under the study conditions. The control group consumed equal amounts of macronutrients, and the higher energy density in this study did not seem to have any benefits. In our study, there was a very intensive follow-up; at every encounter with mothers, giving the required amounts and adding extra lipids was strongly reinforced. Under those conditions, a well-balanced complementary food with additional lipids can meet the energy needs of young children. The reduction in phytates by 34% and improvement in iron solubility to 19% due to processing might not have been enough to compensate for the rather low iron content of the complementary food.

Efeitos da suplementação e da fortificação de alimentos sobre a biodisponibilidade de minerais

Estratégias de prevenção e combate a algumas deficiências nutricionais, como a anemia e a osteoporose, incluem a fortificação de alimentos e o uso de suplementação com minerais em populações de risco. Entretanto, interações com outros minerais podem ocorrer e comprometer o estado de saúde do indivíduo. Este artigo teve por objetivo rever algumas das interações que podem ocorrer entre minerais quando da suplementação ou fortificação de alimentos. A suplementação de cálcio parece estar relacionada a uma diminuição da absorção do zinco, fósforo e ferro. Por sua vez, o excesso de ferro pode comprometer a absorção e utilização do zinco, especialmente quando em formulações antianêmicas. Apesar dos resultados de alguns estudos serem controversos, a suplementação de minerais ou a fortificação de alimentos devem ser cuidadosas a fim de não ocasionar outras deficiências nutricionais.

Home-fortification with iron and zinc sprinkles or iron sprinkles alone successfully treats anemia in infants and young children

Although iron deficiency is the most common single-nutrient deficiency in infants and children, other deficiencies may develop concurrently, including zinc deficiency. In previous studies, we used home-fortification with "Sprinkles," single-serve sachets containing microencapsulated ferrous fumarate added to weaning foods, to successfully treat anemia. This mode of micronutrient delivery is amenable to the delivery of other micronutrients. However, the relative efficacy of multiple micronutrient supplements for the treatment of anemia requires evaluation due to possible nutrient interactions. Thus, we evaluated the relative efficacy of Sprinkles formulated with iron and zinc in anemic infants, compared with Sprinkles formulated with iron alone. We studied 304 anemic infants (mean age 10.3 +/- 2.5 mo; hemoglobin 87.4 +/- 8.4 g/L) in rural Ghana. A combined supplementation group (FeZn) received daily Sprinkles containing 80 mg iron and 10 mg zinc; a comparison group (Fe) received Sprinkles (80 mg iron) without zinc for 2 mo. The rate of recovery from anemia was higher in the Fe group compared with the FeZn group (74.8 vs. 62.9%; P = 0.048). The plasma zinc concentration decreased significantly in both groups (P < 0.05). A significant decline in the height for age Z-score was observed in the FeZn group (P = 0.0011), but there was no change in the Fe group. These results suggest that in a controlled setting, home-fortification using micronutrient Sprinkles with iron, or iron and zinc, was very successful in treating anemia; however, this intervention alone was insufficient to improve zinc status or promote catch-up growth in this stunted and wasted population.

A community-based randomized controlled trial of iron and zinc supplementation in Indonesian infants: interactions between iron and zinc

BACKGROUND

Combined supplementation with iron and zinc during infancy may be effective in preventing deficiencies of these micronutrients, but knowledge of their potential interactions when given together is insufficient.

OBJECTIVE

The goal was to compare the effect in infants of combined supplementation with iron and zinc and of supplementation with single micronutrients on iron and zinc status.

DESIGN

Indonesian infants (n = 680) were randomly assigned to daily supplementation with 10 mg Fe (Fe group), 10 mg Zn (Zn group), 10 mg Fe + 10 mg Zn (Fe+Zn group), or placebo from 6 to 12 mo of age. Venous blood samples were collected at the start and end of the study. Five hundred forty-nine infants completed the supplementation and had both baseline and follow-up blood samples available for analysis.

RESULTS

Baseline prevalences of anemia, iron deficiency anemia (anemia and low serum ferritin), and low serum zinc (< 10.7 micromol/L) were 41%, 8%, and 78%, respectively. After supplementation, the Fe group had higher hemoglobin (119.4 compared with 115.3 g/L; P < 0.05) and serum ferritin (46.5 compared with 32.3 microg/L; P < 0.05) values than did the Fe+Zn group, indicating an effect of zinc on iron absorption. The Zn group had higher serum zinc (11.58 compared with 9.06 micromol/L; P < 0.05) than did the placebo group. There was a dose effect on serum ferritin in the Fe and Fe+Zn groups, but at different levels. There was a significant dose effect on serum zinc in the Zn group, whereas no dose effect was found in the Fe+Zn group beyond 7 mg Zn/d.

CONCLUSION

Supplementation with iron and zinc was less efficacious than were single supplements in improving iron and zinc status, with evidence of an interaction between iron and zinc when the combined supplement was given.

Nutritional aspect of zinc availability

Zinc is an essential trace element in human nutrition and its deficiency is a world nutritional problem. However, the zinc content of foods is low and its availability is conditioned by several physiologic and dietary factors. For that reason, the objective of the present work is to compile past and present information about the influence of these factors on zinc availability to try to improve this availability.

The role of zinc in the growth and development of children

This review concerns the importance of zinc in growth, development, and cognitive function in children and the deleterious consequences of its deficiency on children's health. Possible strategies to overcome zinc deficiency and the results of some supplementation trials are discussed.

Dietary factors influencing zinc absorption

Marginal zinc deficiency and suboptimal zinc status have been recognized in many groups of the population in both less developed and industrialized countries. Although the cause in some cases may be inadequate dietary intake of zinc, inhibitors of zinc absorption are most likely the most common causative factor. Phytate, which is present in staple foods like cereals, corn and rice, has a strong negative effect on zinc absorption from composite meals. Inositol hexaphosphates and pentaphosphates are the phytate forms that exert these negative effects, whereas the lower phosphates have no or little effect on zinc absorption. The removal or reduction of phytate by enzyme (phytase) treatment, precipitation methods, germination, fermentation or plant breeding/genetic engineering markedly improves zinc absorption. Iron can have a negative effect on zinc absorption, if given together in a supplement, whereas no effect is observed when the same amounts are present in a meal as fortificants. Cadmium, which is increasing in the environment, also inhibits zinc absorption. The amount of protein in a meal has a positive effect on zinc absorption, but individual proteins may act differently; e.g., casein has a modest inhibitory effect of zinc absorption compared with other protein sources. Amino acids, such as histidine and methionine, and other low-molecular-weight ions, such as EDTA and organic acids (e.g., citrate), are known to have a positive effect on zinc absorption and have been used for zinc supplements. Knowledge about dietary factors that inhibit zinc absorption and about ways to overcome or remove these factors is essential when designing strategies to improve the zinc nutrition of vulnerable groups.

Long-term effects of iron:zinc interactions on growth in rats

The influence of iron (Fe) on the bioavailability and functional status of zinc (Zn) was studied in young rats using metabolic balances and tissue dosages, which were compared to growth. Diets supplied adequate intakes of Fe (45 and 300 mg/kg diet) and Zn (14 and 45 mg/kg) for 2 mo. Two metabolic balance determinations were performed that were correlated for Zn and Fe during the first and the last weeks of the study. A significant effect of Fe supply, but not of Zn was displayed on Fe absorption; both Fe and Zn diet concentrations had a significant influence on Zn absorption. Fe and Zn organ contents were significantly correlated with the amount absorbed during the two metabolic balances. There was a positive correlation between liver and muscle Fe and Fe absorption, and Fe absorption and muscle Zn, as well as a negative one with liver Zn; a positive correlation was displayed between Zn absorption and Zn organ content. No correlation was found between Zn absorption and Fe tissue content. Growth was correlated with Zn, but not with Fe absorption during both balances. A positive correlation was displayed between growth and Zn liver content, and a negative one with Fe liver content. Care must be taken to give growing subjects balanced diets or supplementation, since the negative interactions between these trace elements are likely to persist as long as the diet is given.

59Fe is retained from an elemental 59Fe powder supplement without effects on 65Zinc, 47Calcium and 67Copper in young pigs

In vivo counting with the use of a germanium detector evaluated the retention of an elemental 59Fe powder supplement while measuring potential interactions with zinc, calcium and copper. Effects of dietary iron and zinc on in vivo retentions of 59Fe, 65Zn, 67Cu and 47Ca were studied in young pigs. In Experiment 1, 4-d-old piglets fed a cereal-based diet were randomly assigned to one of four treatment groups (2 x 2 factorial arrangement, n = 5 per group). Variables were dietary iron source (either elemental iron or FeSO4, each at 100 mg iron/kg diet) and the dosage form of radioactive iron (either elemental 59Fe powder or 59FeSO4). Experiment 2 (2 x 3 factorial arrangement) was performed using two levels of iron (100 and 200 mg/kg, as elemental iron) and three levels of zinc (25, 50 and 100 mg/kg). Piglets were also dosed with 47Ca, 65Zn and 67Cu; all radioisotopes were measured for 8 d. Apparent absorption of elemental 59Fe powder was 13 +/- 1%, whereas 59Fe sulfate was significantly (P < 0.05) higher at 26 +/- 1%. The FeSO4 diet decreased 65Zn retention in Experiment 1, in contrast to the elemental iron diet, which did not have this effect in either experiment. Apparent 65Zn absorption averaged 44 +/- 2, 35 +/- 1 and 27 +/- 2% for the three levels of zinc (25, 50 and 100 mg/kg), respectively. Retention of 47Ca was not affected by dietary iron or zinc; retention of 67Cu was not affected by dietary iron. The data demonstrate good bioavailability of elemental iron without effects on zinc, copper and calcium.

Multiple Fortification of Beverages

Diet-related micronutrient deficiencies rarely occur in isolation; deficiencies of iodine and vitamin A or of iron and vitamin A or zinc are often observed in the same populations. In addition, widespread deficiencies of some micronutrients, for example, zinc and calcium, may often go undiagnosed because of the absence of specific and sensitive status indicators. Multiple micronutrient supplementation can be more effective in improving nutritional status than supplementation with single key micronutrients; therefore, the multiple fortification of appropriate food vectors, including beverages, is of interest from the nutritional standpoint.

Beverages fortified with multiple micronutrients include dairy products, chocolate beverages, fruit juices, and soya-based drinks. As well as the documented or estimated micronutrient deficiencies and the requirements of the target population or consumer group, the conception of such a multiply fortified beverage must take into account a number of other important factors. The choice of the chemical form of the fortification micronutrients should be made with consideration of bioavailability, the effects on the organoleptic characteristics of the particular beverage, and cost. The initial calculation of the composition of the micronutrient premix should include the levels of micronutrients in the raw materials used and the estimated losses of specific micronutrients during processing and storage. Preliminary production and storage trials are then needed to determine the actual losses. The composition of the micronutrient premix may then be finalized. Interactions, both positive and negative, between fortification micronutrients may also need to be considered. For example, the bioavailability of iron may be enhanced by the addition of vitamin C, whereas mineral–vitamin and vitamin–vitamin interactions can accelerate the destruction of some vitamins.

To render quality control procedures simple and cost-effective, only a limited number of fortification micronutrients, which are especially sensitive to losses and which are easy to measure, may be analysed. Simple, inexpensive, and rigorous analytical methods for such measurements are now available.