Effect of beef and soy proteins on the absorption of non-heme iron and inorganic zinc in children

Energy, protein and iron densities of dabi teff-field pea-based optimised novel complementary flour and its contribution to daily energy and nutrients demand by 6-23-month-old children

Inadequate intake of age-specific energy and nutrients is among the prime immediate causes of child malnutrition. Thus, this study aimed to determine the energy, protein and Fe densities of pre-processed dabi teff-field pea-based optimised novel complementary flour and its contribution to daily energy and nutrients demand by 6-8, 9-11 and 12-23 month-old children. The optimal formula at overall optimisation was identified to be 34·66 % dabi teff, 25 % barley, 15 % oats, 15·34 % field pea, 5 % linseed and 5 % maize with response values of 15·74 % protein, 5·09 % fat, 2·26 % ash, 2·88 % fibre, 73·05 % carbohydrate, 1591·72 kJ/100 g (380·43 kcal/100 g) energy, 32·21 mg/100 g Fe, 77·51 mg/100 g Ca and 2·59 mg/100 g Zn. The energy density of the optimised novel complementary flour was 1·27 kcal/g which fulfilled the Pan American Health Organization/WHO recommendation (≥ 0·8 kcal/g), protein density was 4·14 g/100 kcal and the Fe density was 8·47 mg/100 kcal, which was 2·12 to 10·59 times higher than the recommended value where the optimal had demonstrated to contribute more than 100 % of the daily energy and protein demand and notably more than 200 % of daily Fe demand at moderate bioavailability (0·8-4 mg/100 kcal). These findings showed that the daily recommended dietary allowance for energy, protein and Fe could be attained by the developed dabi teff-field pea-based optimised novel complementary flour and its contribution to the children's daily energy and nutrients demand met the standard, where the product can be used as food-based nutrition intervention to manage protein-energy malnutrition and Fe deficiency anemia in children sustainably.

Iron Nutrition of Pre-Schoolers in High-Income Countries: A Review

Pre-schoolers are vulnerable to iron deficiency, which, in high-resource countries, is mainly caused by suboptimal or poorly absorbable iron intakes. This review examines the prevalence of inadequate iron intakes and status, and the non-dietary factors associated with these, among children aged between 2 and 5 years within high-income countries. It then considers the quality of the pre-schooler diet in terms of dietary factors, dietary patterns, and iron intakes. Additionally, it discusses the assessment of iron bioavailability and examines the various methods used to estimate the amount of absorbable iron in pre-schooler diets. Knowledge of the adequacy of iron intakes and bioavailability of iron intakes, and dietary patterns associated with iron intakes can facilitate the design and implementation of effectively targeted community-based intervention studies to improve iron intakes and iron bioavailability to minimise the risk of iron deficiency.

The Effect of the Meat Factor in Animal-Source Foods on Micronutrient Absorption: A Scoping Review

The EAT-Lancet Commission's planetary health guidelines suggest a reduction in the consumption of animal-source foods (ASFs) for better health and more sustainable food systems. ASFs are highly nutrient dense, therefore suited to address the widespread issue of micronutrient deficiencies, particularly in low-resource settings where diets are predominantly plant based. ASFs are also believed to contain the meat factor, a substance enhancing the absorption of micronutrients from plant-based foods. We conducted a scoping review with the objective of systematically mapping the available evidence on the meat factor. The MEDLINE/PubMed and Web of Science databases were searched for literature published up to September 2021. Articles eligible for inclusion were all studies assessing the effect of adding ASFs and/or ASF fractions on micronutrient absorption from a plant-based meal or the overall diet in animal models and human subjects. Screening and data extraction were performed, and results were charted into 12 categories. We identified 77 articles eligible for inclusion, 52 of which were conducted in human subjects, 24 in animal models, and 1 in both. The addition of muscle tissue and muscle tissue fractions to single plant-based meals steadily increased absorption of iron and zinc across studies. The efficacy of the meat factor in increasing iron and zinc absorption in the overall diet is less clear. No clear differences emerged between red meat, poultry, and fish in promoting the meat factor effect. No clear evidence indicates that milk and egg products contain the meat factor. Our review highlights the importance of muscle tissue for the potential of the meat factor to enhance absorption of micronutrients of concern. Although the literature supports including sustainable and economically accessible forms of these ASFs into the diet, we found limited studies in resource-poor countries and of diets with low meat intake.

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.

Lower Non-Heme Iron Absorption in Healthy Females from Single Meals with Texturized Fava Bean Protein Compared to Beef and Cod Protein Meals: Two Single-Blinded Randomized Trials

Meat analogs based on plant protein extracts are rising in popularity as meat consumption declines. A dietary shift away from meat, which has a high iron bioavailability, may have a negative effect on the amount of iron absorbed from the diet. Iron absorption from legumes cultivated in regions not suitable for soy production, such as fava bean, has not yet been explored. The aim of this study was to evaluate non-heme iron absorption from a meal with texturized fava bean protein compared to beef and cod protein meals. The study included two single-blinded iron isotope trials in healthy Swedish women of the ages 18–45 years, each of whom served as their own control. The participants were served matched test meals containing beef and fava bean protein (Study 1) or cod and fava bean protein (Study 2) with radiolabeled non-heme iron 55Fe and 59Fe. The absorption of non-heme iron from test meals was measured by whole-body counting and erythrocyte incorporation. The absorption of non-heme iron, measured as erythrocyte incorporation ratio, from beef protein meal was 4.2 times higher compared to texturized fava bean meal, and absorption from cod protein meal was 2.7 times higher compared to the fava bean meal. The adjusted non-heme iron absorption, normalized to a 40% reference dose uptake, was 9.2% for cod protein meal, 21.7% for beef protein meal, and 4.2% for texturized fava bean meal. A fava bean protein meal has markedly lower iron bioavailability in healthy females compared with a meal of beef or cod protein. Therefore, a dietary shift from meat and fish protein to fava bean protein may increase the risk of iron deficiency.

Purified Dietary Red and White Meat Proteins Show Beneficial Effects on Growth and Metabolism of Young Rats Compared to Casein and Soy Protein

This study compared the effects of casein, soy protein (SP), red (RMP), and white meat (WMP) proteins on growth and metabolism of young rats. Compared to casein, the ratio of daily feed intake to daily body weight gain of rats was not changed by meat protein but reduced by SP by 93.3% ( P < 0.05). Feeding RMP and WMP reduced the liver total cholesterol (TC) contents by 24.3% and 17.8%, respectively ( P < 0.05). Only RMP increased plasma HDL-cholesterol concentrations (by 12.7%, P < 0.05), whereas SP increased plasma triacylglycerol, TC, and LDL-cholesterol concentrations by 23.7%, 19.5%, and 61.5%, respectively ( P < 0.05). Plasma essential and total amino acid concentrations were increased by WMP (by 18.8% and 12.4%, P < 0.05) but reduced by SP (by 28.3% and 37.7%, P < 0.05). Twenty-five liver proteins were differentially expressed in response to different protein sources. Therefore, meat proteins were beneficial for growth and metabolism of young rats compared to casein and SP.

Zinc Fractional Absorption from a Representative Diet in Young Chinese Men and Women of the Shandong Rural Region

The objective of this study was to investigate the zinc fractional absorption of young Chinese men and women from the Shandong rural region under the routine dietary pattern by stable isotope technique. Ten men and 10 women, aged 20 to 35 years, and with a representative diet during the experiment were recruited from the Shandong rural region. Stable ⁶⁷Zn was used as a tracer to label ZnCl₂, and Yb was used to monitor the excretion of ⁶⁷Zn in urine and feces. All volunteers were given rice containing 4.0 mg ⁶⁷Zn and 1.0 mg Yb on the fourth day. Then the food and fecal samples of all subjects were collected for 12 consecutive days. The total zinc and the stable zinc isotope ratio of all samples were determined by atomic absorption spectrophotometer and thermal ionization mass spectrometer, respectively. The determination of the other nutrients was performed based on the Chinese National Standard Methods. Among volunteers, the daily intake of zinc was 15.50 mg, 103.33 % of recommended nutrient intake (RNI, set by the Chinese Nutrition Society) in men and 15.43 mg, 134.17 % in women. The fractional absorption of Zn was 23.42 ± 2.23 % in men, and 22.49 ± 2.19 % in women. The protein candidates got from the typical diets was 93.96 % of RNI in women. Calcium and ascorbic acid intakes were 76.23 % of RNI and 27.91 % of RNI in men, respectively and 51.17 % of RNI and 34.23 % of RNI in women, respectively. Our results showed that a typical meal for someone in the Shandong rural region presented an adequate intake of zinc and a moderate Zn bioavailability. The shortage of protein and the inappropriate protein pattern may play important roles in reducing zinc bioavailability.

Non-Heme Iron Absorption and Utilization from Typical Whole Chinese Diets in Young Chinese Urban Men Measured by a Double-Labeled Stable Isotope Technique

BACKGROUND

This study was to observe the non-heme iron absorption and biological utilization from typical whole Chinese diets in young Chinese healthy urban men, and to observe if the iron absorption and utilization could be affected by the staple food patterns of Southern and Northern China.

MATERIALS AND METHODS

Twenty-two young urban men aged 18-24 years were recruited and randomly assigned to two groups in which the staple food was rice and steamed buns, respectively. Each subject received 3 meals containing approximately 3.25 mg stable 57FeSO4 (the ratio of 57Fe content in breakfast, lunch and dinner was 1:2:2) daily for 2 consecutive days. In addition, approximately 2.4 mg 58FeSO4 was administered intravenously to each subject at 30-60 min after dinner each day. Blood samples were collected from each subject to measure the enrichment of the 57Fe and 58Fe. Fourteen days after the experimental diet, non-heme iron absorption was assessed by measuring 57Fe incorporation into red blood cells, and absorbed iron utilization was determined according to the red blood cell incorporation of intravenously infused 58Fe SO4.

RESULTS

Non-heme iron intake values overall, and in the rice and steamed buns groups were 12.8 ±2.1, 11.3±1.3 and 14.3±1.5 mg, respectively; the mean 57Fe absorption rates were 11±7%, 13±7%, and 8±4%, respectively; and the mean infused 58Fe utilization rates were 85±8%, 84±6%, and 85±10%, respectively. There was no significantly difference in the iron intakes, and 57Fe absorption and infused 58Fe utilization rates between rice and steamed buns groups (all P>0.05).

CONCLUSION

We present the non-heme iron absorption and utilization rates from typical whole Chinese diets among young Chinese healthy urban men, which was not affected by the representative staple food patterns of Southern and Northern China. This study will provide a basis for the setting of Chinese iron DRIs.

Food-Based Interventions to Modify Diet Quality and Diversity to Address Multiple Micronutrient Deficiency

Global data indicate a high prevalence of hidden hunger among population. Deficiencies of certain micronutrients such as folic acid, iodine, iron, and vitamin A have long lasting effects on growth and development and therefore have been a National priority from many decades. The strategy implemented so far limits to the use of supplemental sources or fortified foods in alleviating the burden of deficiencies. These approaches however undermine the food-based strategies involving dietary diversification as the long-term sustainable strategy. There is lack of understanding on the level of evidence needed to implement such strategies and the level of monitoring required for impact evaluation. Dietary diversity concerns how to ensure access for each individual to a quality and safe diet with adequate macro- and micronutrients. The key to success in using dietary diversity as a strategy to tackle hidden hunger is in integrating it with the principles of bioavailability, translated to efficient food synergies with due emphasis on food accessibility, affordability, and outdoor physical activity/life style modifications. Promoting enabling environment and sustainable agriculture is crucial for practicing dietary diversification with behavior change communication as an integral segment. It can be concluded that food-based strategies require careful understanding of the factors associated with it and moderate it to form an effective strategy for controlling multiple micronutrient deficiencies.

Dietary iron depletion at weaning imprints low microbiome diversity and this is not recovered with oral Nano Fe(III)

Alterations in the gut microbiota have been recently linked to oral iron. We conducted two feeding studies including an initial diet-induced iron-depletion period followed by supplementation with nanoparticulate tartrate-modified ferrihydrite (Nano Fe(III): considered bioavailable to host but not bacteria) or soluble ferrous sulfate (FeSO₄: considered bioavailable to both host and bacteria). We applied denaturing gradient gel electrophoresis and fluorescence in situ hybridization for study-1 and 454-pyrosequencing of fecal 16S rRNA in study-2. In study-1, the within-community microbial diversity increased with FeSO₄ (P = 0.0009) but not with Nano Fe(III) supplementation. This was confirmed in study-2, where we also showed that iron depletion at weaning imprinted significantly lower within- and between-community microbial diversity compared to mice weaned onto the iron-sufficient reference diet (P < 0.0001). Subsequent supplementation with FeSO₄ partially restored the within-community diversity (P = 0.006 in relation to the continuously iron-depleted group) but not the between-community diversity, whereas Nano Fe(III) had no effect. We conclude that (1) dietary iron depletion at weaning imprints low diversity in the microbiota that is not, subsequently, easily recovered; (2) in the absence of gastrointestinal disease iron supplementation does not negatively impact the microbiota; and (3) Nano Fe(III) is less available to the gut microbiota.

Body image concerns: levels, correlates and gender differences among students in the United Kingdom

AIMS

This cross-sectional study aimed to determine the socio-demographic, lifestyle and well-being variables that are associated with body image concerns (BIC) and whether these associations differed between female and male students.

METHODS

A cross-sectional survey; 3,706 undergraduate students (2,699 females, 765 males) from seven universities in the UK completed a self-administered questionnaire that assessed socio-demographic, lifestyle, well-being and BIC based on the Body Shape Questionnaire developed by Cooper et al. Multifactorial logistic regression analysis examined the odds ratios for the association between four increasing levels of BIC as the dependent variables (no BIC, mild BIC, moderate BIC and marked BIC) on the one hand, and the socio-demographic (gender, age, year at university), lifestyle (physical activity, nutrition) and mental well-being variables (quality of life, perceived stress, perceived health, depressive symptoms) on the other.

RESULTS

More females (35%) than males (8%) reported being moderately or markedly concerned with their body image. For both genders, BIC was associated with a higher level of depressive symptoms and to variable extents, with nutrition and year at university. Females' BICs were exclusively associated with low perceived health, higher perceived stress, studies in general as a stressor, and low physical activity. In contrast, males' BIC were found to be exclusively associated with low quality of life and with older age.

CONCLUSIONS

Health promoting strategies and activities should address the co-occurrence of depressive symptoms and BIC and should moreover pay attention to the gender-specific correlates of BIC for tailoring evidence based interventions for females and for males.

Inclusion of red meat in healthful dietary patterns

Dietary patterns are an important concept in dietary recommendations. The Western pattern is most commonly defined as a diet characterized by high intakes of refined grains, sugar and red meat, and has been shown to be associated with increased risks for certain types of cancer, coronary heart disease, diabetes, and obesity. However, isolating the independent effects of individual foods on health outcomes is central to helping individuals choose foods to build healthier dietary patterns to which they can adhere. Red meat is a popular source of high quality protein and provides a variety of essential nutrients that improve overall diet quality. It is also a source of saturated fatty acids, which observational evidence suggests are associated with heart disease, although recent data challenge this. Several studies have shown that lean red meat can be successfully included in recommended heart-healthy dietary patterns without detriment to blood lipids. Furthermore, increased dietary protein has been shown to promote healthy body weight and composition, in part by increasing satiety, and to improve vitality and stamina.

Relationships of maternal zinc intake from animal foods with fetal growth

Zn is an essential element for human growth. The nutritional adequacy of dietary Zn depends not only on the total Zn intake, but also on the type of food source (i.e. of plant or animal origin). We investigated the association between maternal dietary Zn intake from animal and plant food sources and fetal growth. A total of 918 pregnant women at 12-28 weeks of gestation were selected from the Mothers and Children's Environmental Health study in Korea. Dietary intakes in mid-pregnancy were estimated by a 24 h recall method, and subsequent birth weight and height were obtained from medical records. Multiple regression analysis showed that maternal Zn intake from animal food sources and their proportions relative to total Zn intake were positively associated with birth weight (P = 0.034 and 0.045, respectively) and height (P = 0.020 and 0.032, respectively). Conversely, the percentage of Zn intake from plant food sources relative to total Zn intake was negatively associated with birth height (P = 0.026) after adjustment for covariates that may affect fetal growth. The molar ratio of phytate:Zn was negatively associated with birth weight (P = 0.037). In conclusion, we found that the absolute amounts of Zn from different food sources (e.g. animal or plant) and their proportions relative to total Zn intake were significantly associated with birth weight and height. A sufficient amount of Zn intake from animal food sources of a relatively higher Zn bioavailability is thus encouraged for women during pregnancy.

Sense of coherence and health-related behaviour among university students--a questionnaire survey

The aim of this study is to evaluate the relation between a sense of coherence and intensity of health-related behaviour among 521 Polish university students. The study was conducted using validated instruments with two questionnaires: Antonovsky's SOC-29 and the Inventory of Health-Related Behaviour. The mean value of SOC amounted to 125.2. More than half of the studied group were characterized by the average level of SOC. No statistical differences were found between the faculty of study and SOC (p = 0.107). A low intensity of health-related behaviour characterized a large group of students. Students of particular faculties differ among themselves in a statistically significant way in the level of health-related behaviour (p = 0.015). SOC is related to healthy behaviour (p < 0.001). University students are often characterized by an average level of SOC and a low intensity of health-related behaviour. Medical students are characterized by higher level of health-related behaviour in comparison with humanistic and science students. SOC correlates positively with a tendency to health-related behaviour. The higher the level of coherence, the higher is the tendency towards pro-health behaviour.

The role of soy in vegetarian diets

Soyfoods have long been prized among vegetarians for both their high protein content and versatility. Soybeans differ markedly in macronutrient content from other legumes, being much higher in fat and protein, and lower in carbohydrate. In recent years however, soyfoods and specific soybean constituents, especially isoflavones, have been the subject of an impressive amount of research. Nearly 2,000 soy-related papers are published annually. This research has focused primarily on the benefits that soyfoods may provide independent of their nutrient content. There is particular interest in the role that soyfoods have in reducing risk of heart disease, osteoporosis and certain forms of cancer. However, the estrogen-like effects of isoflavones observed in animal studies have also raised concerns about potential harmful effects of soyfood consumption. This review addresses questions related to soy and chronic disease risk, provides recommendations for optimal intakes, and discusses potential contraindications. As reviewed, the evidence indicates that, with the exception of those individuals allergic to soy protein, soyfoods can play a beneficial role in the diets of vegetarians. Concerns about adverse effects are not supported by the clinical or epidemiologic literature. Based on the soy intake associated with health benefits in the epidemiologic studies and the benefits noted in clinical trials, optimal adult soy intake would appear to be between two and four servings per day.

Changing the zinc:iron ratio in a cereal-based nutritional supplement has no effect on percent absorption of iron and zinc in Sri Lankan children

The Thriposha programme is a community-level nutrition intervention in Sri Lanka that provides a combination of energy, protein and micronutrients as a ‘ready-to-eat’ cereal-based food. We measured the bioavailability of Fe and Zn from Thriposha formula at two different molar ratios of Zn:Fe in order to determine the effect on Fe and Zn absorption. Children 4–7 years (n 53) were given a meal prepared with 50 g Thriposha containing 1·5 mg Zn as zinc sulphate and either 9 mg (high Fe concentration (HiFe)) or 4·5 mg (low Fe concentration (LoFe)) Fe as ferrous fumarate. Zn and Fe percent absorption were measured using stable isotopes by tracer:tracee ratio and by incorporation of erythrocytes, respectively. Percent Fe absorption from the two meals was similar (6·6 % (4·8) v. 4·8 % (2·6); P = 0·15), but total Fe absorption was significantly higher from the HiFe meal (0·59 (0·43) mg) than the LoFe meal (0·20 (0·12) mg; P = 0·01). There was no significant difference between the two groups in Zn absorption (10·7 % (0·9) v. 8·8 % (1·4), P = 0·13, respectively). Decreasing the amount of Fe in Thriposha did not cause a significant change in the percent absorption of Fe and Zn, but significantly lowered the total amount of absorbed Fe. These results demonstrate the utility of maintaining a higher Fe content in this supplement. Further studies to increase Zn content are warranted while maintaining a HiFe.

Dietary inulin supplementation does not promote colonic iron absorption in a porcine model

Prebiotics may enhance iron bioavailability by increasing iron absorption in the colon. Anemic pigs fitted with cecal cannulas were fed a low-iron diet with or without 4% inulin. Over 7 days, pigs were administered 1 mg of (54)Fe in the morning feed followed by cannula infusion of 0.5 mg of (58)Fe to measure total and colonic iron absorption, respectively. Whole blood was drawn prior to the initial dosing and 14 days thereafter for hemoglobin concentration and stable isotope ratio analyses. The prebiotic role of inulin was confirmed by increases in lactobacilli and bifidobacteria with reductions in clostridia using terminal restriction fragment length polymorphism (TRFLP). Total iron absorption was 23.2 +/- 2.7 and 20.7 +/- 3.5% (mean +/- SEM; p > 0.05), while colonic iron absorption was 0.4 +/- 0.1 and 1.0 +/- 0.2% (mean +/- SEM; p > 0.05) in inulin-fed and control pigs, respectively. These results show that the colon does not make a significant contribution to total iron absorption in iron-deficient pigs and that inulin does not affect iron absorption in the colon.

A Review of Interventions Based on Dietary Diversification or Modification Strategies with the Potential to Enhance Intakes of Total and Absorbable Zinc

Dietary diversification or modification has the potential to prevent deficiencies of zinc and other coexisting limiting micronutrients simultaneously, without risk of antagonistic interactions. In this review, we have addressed the following. The first section focuses on strategies with the potential to enhance intake and/or bioavailability of zinc, and includes interventions (with and without nutrition education) based on agriculture, production or promotion of animal-source foods through animal husbandry or aquaculture, and commercial and household processing strategies to enhance zinc absorption. Outcome indicators include intakes of foods or nutrients (although rarely zinc) and, in some cases, zinc status, or zinc-related functional responses. The next two sections address whether dietary diversification or modification can achieve increases in absorbable zinc that are sufficient to enhance zinc status or zinc-related functional responses in breastfed infants and toddlers and in older children and women of reproductive age. Evidence for the impact of dietary diversification or modification on behavior change and on nutritional status in the short and long term, and the possible role of modifying factors (e.g., baseline nutritional status, socioeconomic status, infection, sex, age, and life-stage group) is the emphasis of the next section. The following section highlights the evidence for three potential adverse effects of dietary diversification or modification: aflatoxin contamination from germinated cereals, loss of water-soluble nutrients, and displacement of breastmilk. Finally, an example of a dietary diversification or modification program (Homestead Food Production) developed and implemented by Helen Keller International is given, together with the critical steps needed to scale up dietary diversification or modification for programs and future research needs.

Zinc homeostasis in 1–4 year olds consuming diets typical of US children

Few data have evaluated Zn balance in young children after the first year of life. The objective of the present study was to study the relationships among Zn intake, absorption, endogenous faecal excretion, and retention in a group of healthy children. Thirty children, aged 15–48 months, were studied on a diet representative of their usual daily mineral intake. Zn absorption was assessed using a dual-tracer stable-isotope technique. Endogenous Zn faecal excretion and Cu absorption were determined in a subset of children. We found that Zn intake from the in-patient weighed dietary record (5·0 (sd 2·1) mg/d) was significantly greater than the current estimated average requirement (EAR; 2·5 mg/d; P < 0·0001). Neither fractional Zn absorption, urinary Zn excretion, nor endogenous faecal Zn excretion was significantly related to Zn intake (r2 < 0·1; P>0·4, for all). Absolute Zn absorption was significantly related to Zn intake (r2 0·696; P < 0·0001), as was Zn retention (r2 0·506; P < 0·0001). Cu absorption was relatively high (75·1 (sd 10·8) %) despite the high Zn intake. The EAR for Zn based on this dataset would appear to be between 4·2 and 4·7 mg/d to allow for a net average retention of 120 μg/d consistent with growth needs. We concluded that at relatively high Zn intakes there was little evidence of down regulation of absorption or up regulation of urinary or endogenous faecal Zn excretion across the intake range studied. Zn retention was positively correlated with intake. A Zn intake between 4·2 and 4·7 mg/d should meet the requirement for normal growth for this age group.

Iron requirements, absorption and metabolism in infancy and childhood

PURPOSE OF REVIEW

Iron deficiency is a significant public health problem in young children due to their high iron requirements, and iron supplements are therefore often recommended. During the time period in focus for this review (2005-2006), there have been additional advances in our understanding of the molecular mechanisms of iron absorption and metabolism. It has also been suggested that iron supplements may have adverse effects in children.

RECENT FINDINGS

Recently discovered molecules, for example hepcidin, lactoferrin receptor and heme carrier protein may be important for iron metabolism in children. There are possible metabolic interactions between iron and several other minerals. Many studies show that iron deficiency in young children is associated with impaired neurodevelopment but it is not clear whether this can be prevented by iron supplementation. Oral iron supplements given to young children in malarious regions may lead to increased risk of death or severe infections, especially in those who are iron replete.

SUMMARY

More research is needed to identify those children who will benefit from iron supplementation and to better determine iron requirements during early life. Clinical trials should include functional outcomes. Better knowledge about molecular mechanisms and nutrient interactions may lead to new diagnostic tests and preventive strategies.

Production of stable-isotope-labeled bovine heme and its use to measure heme-iron absorption in children

BACKGROUND

The use of stable isotopes has provided valuable insights into iron absorption in humans, but the data have been limited to nonheme iron.

OBJECTIVE

Our objectives were to produce heme iron enriched in (58)Fe and to use it to study the absorption of heme iron and the effect of iron and zinc intakes on heme-iron absorption in children.

DESIGN

Labeled bovine heme was produced in a bovine model. Forty-eight children were randomly assigned to consume identical meals containing 1 of 3 doses of labeled heme iron (2, 4, or 8 mg as hemoglobin) and 1 of 2 doses of inorganic zinc (1 or 9 mg); successful measurements of iron absorption, zinc absorption, or both were made in 40 of these subjects. We hypothesized that fractional heme-iron absorption would decrease as heme-iron intake increased and that higher zinc intakes would decrease heme-iron absorption.

RESULTS

(58)Fe heme was produced with an enrichment (mass/mass) of 9.5%. Fractional iron absorption in children was significantly affected by the intake of heme iron (P = 0.0013) and of zinc (P = 0.0375), but, contrary to expectations, heme-iron absorption was higher at higher zinc intakes. Absolute heme-iron absorption was higher in the group with higher zinc intakes, but only for those with the lowest heme-iron intake (2 mg; P = 0.0147). Although fractional zinc absorption decreased as zinc intake increased (P = 0.031), absolute zinc absorption continued to increase across the intake range studied (P = 0.018).

CONCLUSIONS

Heme iron intrinsically labeled with (58)Fe can be produced at sufficient enrichments for use in human studies. In children, heme iron and zinc absorption decrease as the dose of each mineral increases. Heme iron did not inhibit zinc absorption. At lower heme intakes, zinc intakes may increase heme-iron absorption.