The influence of meat on nonheme iron absorption in infants

Iron - a background article for the Nordic Nutrition Recommendations 2023

Iron absorption from foods is generally lower than that of most other nutrients and is highly variable depending on individual iron status and iron bioavailability in the meal. Several large population groups in the Nordic and Baltic countries are at risk of iron deficiency, including infants, young children, menstruating females, pregnant women as well as vegetarians. Iron deficiency leads to anemia, fatigue, and limited capacity for physical activity. Of particular concern is that iron deficiency anemia in young children is associated with impaired neurodevelopment. A comprehensive literature search has been performed and summarized. New factorial calculations have been performed considering iron losses, iron absorption and iron requirements in various population groups. Recent data on iron intakes and the prevalence of iron deficiency in the Nordic countries are presented. Average requirements and tentative recommended intakes are presented for 12 different population groups. Pregnant women and those with high menstrual blood losses should consume iron-rich food and undergo screening for iron deficiency. Infants should consume iron-rich complementary foods and cow's milk should be avoided as a drink before 12 months of age and limited to < 500 mL/day in toddlers. Vegetarians should consume a diet including wholegrains, legumes, seeds, and green vegetables together with iron absorption enhancers. There is no evidence that iron intake per se increases the risk of cancer or diabetes. Iron absorption from foods is generally lower than that of most other nutrients and can vary between <2 and 50% depending on individual iron status and iron bioavailability in the meal.

Iron Absorption: Factors, Limitations, and Improvement Methods

Iron is an essential element for human life since it participates in many functions in the human body, including oxygen transport, immunity, cell division and differentiation, and energy metabolism. Iron homeostasis is mainly controlled by intestinal absorption because iron does not have active excretory mechanisms for humans. Thus, efficient intestinal iron bioavailability is essential to reduce the risk of iron deficiency anemia. There are two forms of iron, heme and nonheme, found in foods. The average daily dietary iron intake is 10 to 15 mg in humans since only 1 to 2 mg is absorbed through the intestinal system. Nutrient-nutrient interactions may play a role in dietary intestinal iron absorption. Dietary inhibitors such as calcium, phytates, polyphenols and enhancers such as ascorbic acid and proteins mainly influence iron bioavailability. Numerous studies have been carried out for years to enhance iron bioavailability and combat iron deficiency. In addition to traditional methods, innovative techniques are being developed day by day to enhance iron bioavailability. This review will provide information about iron bioavailability, factors affecting absorption, iron deficiency, and recent studies on improving iron bioavailability.

Iron-Enriched Nutritional Supplements for the 2030 Pharmacy Shelves

Iron deficiency (ID) affects people of all ages in many countries. Due to intestinal blood loss and reduced iron absorption, ID is a threat to IBD patients, women, and children the most. Current therapies can efficiently recover normal serum transferrin saturation and hemoglobin concentration but may cause several side effects, including intestinal inflammation. ID patients may benefit from innovative nutritional supplements that may satisfy iron needs without side effects. There is a growing interest in new iron-rich superfoods, like algae and mushrooms, which combine antioxidant and anti-inflammatory properties with iron richness.

Assessment of nutrients effect on the bioaccessibility of Cd and Cu in contaminated soil

Soil is considered as a sink for heavy metals. Human health is severely affected by the continuous intake of toxic heavy metals even in a very low concentration. In the present experiment, we determined the influence of nutritional status including control (fasted condition), glucose (fed state), plant protein (fed state), animal protein (fed state) and calcium (fed state) on soil cadmium (Cd) and copper (Cu) bioaccessibility using physiologically-based extraction test (PBET) method together with simulator of the human intestinal microbial ecosystem (SHIME) model. The bioaccessibility of Cd was 1.06-73.58%, 0.44-54.79% and 0-17.78% and Cu was 3.81-67.32%, 4.98-71.14%, and 0-17.54% in the phase-I, phase-II and Phase-III respectively (in this study gastric phase, small intestinal phase and colon phase were considered as phase-I, phase-II and Phase-III respectively). The outcomes showed that, the average Cd bioaccessibility was higher with animal protein addition compared with other treatments in different phases. So, the effect of animal protein on Cd bioaccessibility was higher than other treatments in the phase-I, phase-II and phase-III. Due to the addition of plant protein, the higher average bioaccessibility of Cu was noticed in phase-I and phase-II in comparison to other treatments. However, in phase-III, the higher average bioaccessibility of Cu was found due to control treatment comparing with other treatments. Therefore, the influence of plant protein was higher than other nutrients on Cu bioaccessibility in the phase-I and phase-II. Moreover, other nutrients showed variable influence on Cd and Cu bioaccessibility. So, nutritional status has a significant effect on bioaccessibility as well as human health risk assessment.

Spray-Dried Whey Protein Concentrate-Iron Complex: Preparation and Physicochemical Characterization

Poor absorption of iron from food and oral iron formulations results in extensive use of high-dose oral iron, which is not tolerated. Disposal of whey, a byproduct of the cheese industry, causes environmental pollution. Whey proteins have the ability to bind significant amount of iron, thereby reducing its chemical reactivity and incompatibility with other components in foods. To make iron compatible with food, it was complexed with whey protein concentrate (WPC). After complexation, centrifugation and ultrafiltration techniques were utilised to eliminate the insoluble and free iron from the solution. To enable the availability of whey protein concentrate–iron (WPC–Fe) complex in the powder form, spray drying technique was used. Optimized spray drying conditions used for the preparation were: inlet temperature 180 °C, flow rate 2.66 mL/min and solution of total solids 15%. The complex was observed to be stable under different processing conditions. The in vitro bioaccessibility (iron uptake) of the bound iron from the WPC–Fe complex was significantly higher (p<0.05) than that from iron(II) sulphate under simulated gastrointestinal conditions. WPC–Fe complex with improved iron bioaccessibility could safely substitute iron fortificants in different functional food preparations.

Iron Bioavailability from Pate Enriched with Encapsulated Ferric Pyrophosphate or Ferrous Gluconate in Rats

Fortifying food with iron has been widely studied as a strategy to prevent iron deficiency anaemia. This work comparatively assessed the bioavailability of two forms of iron, ferrous gluconate or ferric pyrophosphate encapsulated in liposomes (lipofer®), when used as fortificants in meat pate. Three groups of growing rats consumed during 28 days either a control diet (AIN-93G), or two diets prepared with enriched pate as the unique source of iron and fat. Body weight and diet intake were measured weekly, and during the last week faeces were collected. On day 28 animals were sacrificed, livers and spleens were removed and stored. Haemoglobin and total iron binding capacity (TIBC) were determined. There were not significant differences among the three groups in body weight and apparent iron absorption, although food intake in the two pate groups was significantly higher compared to the control group. There were not differences in liver and spleen iron content and concentration, neither in haemoglobin and TIBC values. These results indicated that iron bioavailability of pate enriched with ferrous gluconate or ferric pyrophosphate encapsulated in liposomes was similar, and thus both sources of iron are good candidates to be used as fortifiers in meat based products. The present outcome needs to be validated in humans.

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.

Bioavailability of micronutrients: stable isotope techniques to develop effective food-based strategies to combat micronutrient deficiencies

BACKGROUND

The prevalence of micronutrient deficiencies, in particular those of iron, vitamin A, iodine, and zinc, is unacceptably high, especially among infants, children, and women of childbearing age in developing countries. Effective food-based strategies to combat these public health problems are therefore urgently needed.

OBJECTIVE

As only a fraction of dietary iron, zinc, and provitamin A carotenoids is absorbed and utilized, i.e., bioavailable, access to information on micronutrient bioavailability is crucial in the development of food fortification strategies and interventions based on dietary diversification.

METHODS

Review of literature.

RESULTS AND CONCLUSIONS

This overview highlights the usefulness of stable isotope techniques to assess the bioavailability of nonheme iron and provitamin A carotenoids and the importance of generating data on micronutrient bioavailability to move the agenda forward.

Food-based strategies improve iron status in toddlers: a randomized controlled trial12

BACKGROUND

Nonanemic iron deficiency is common in toddlers in developed countries. Food-based strategies are safe methods to control and prevent mild micronutrient deficiencies.

OBJECTIVE

Our objective was to determine the efficacy of an increased intake of red meat, or the consumption of iron-fortified milk, in improvement of iron status in toddlers at a population level.

DESIGN

In this 20-wk randomized placebo-controlled trial, 225 healthy nonanemic 12-20-mo-old children were assigned to 1 of 3 groups: red meat (toddlers encouraged to consume approximately 2.6 mg iron from red meat dishes daily), fortified milk [toddlers' regular milk replaced with iron-fortified (1.5 mg iron/100 g prepared milk) cow milk], or control [toddlers' regular milk replaced with nonfortified (0.01 mg iron/100 g prepared milk) cow milk]. Blood samples were collected at baseline and at 20 wk for hemoglobin, serum ferritin, serum transferrin receptor, and C-reactive protein. The prevalence of suboptimal iron status (ie, depleted iron stores, iron-deficient erythropoiesis, and iron deficiency anemia) was determined, and body iron was calculated.

RESULTS

No intervention effects were shown on the prevalence of suboptimal iron status. Serum ferritin increased by 44% (95% CI: 14%, 82%; P = 0.002) in the fortified milk group, did not change (+10%) in the red meat group (95% CI: -7%, 30%; P = 0.241), and tended to decrease (-14%) in the control group (95% CI: -27%, 1%; P = 0.063). By 20 wk, in comparison with the control group, serum ferritin and body iron were significantly higher in the fortified milk group (both P < 0.001), and serum ferritin was significantly higher in the red meat group (P = 0.033).

CONCLUSIONS

Consumption of iron-fortified milk can increase iron stores in healthy nonanemic toddlers, whereas increased intakes of red meat can prevent their decline. This trial was registered at actr.org.au as ACTRN12605000487617.

Thrombocytopenia and anemia in infants and children

Thrombocytopenia and anemia are the two most common hematologic conditions seen in the pediatric emergency department. Providers of emergency pediatric care must have an understanding of the causes and therapies for the various conditions that result from thrombocytopenia and anemia. This article reviews the common causes of isolated thrombocytopenia and anemia in infancy and childhood.

Oily fish increases iron bioavailability of a phytate rich meal in young iron deficient women

BACKGROUND

Iron deficiency is a major health problem worldwide, and is associated with diets of low iron bioavailability. Non-heme iron absorption is modulated by dietary constituents, one of which is the so-called "meat factor", present in meat, fish (oily and lean) and poultry, which is an important enhancer of iron absorption in humans. Food processing also affects iron bioavailability.

OBJECTIVE

To evaluate the effect of consuming sous vide cooked salmon fish on non-heme iron bioavailability from a bean meal, rich in phytate, in iron-deficient women.

DESIGN

Randomized crossover trial in 21 young women with low iron stores (ferritin < 30 microg/L). Two test meals were extrinsically labelled with stable isotopes of iron (Fe-57 or Fe-58). Iron bioavailability was measured as the incorporation of stable isotopes into erythrocytes 14 d after meals consumption.

RESULTS

The addition of fish to the bean meal significantly increased (p < 0.001) iron absorption. Serum ferritin concentration and iron absorption were inversely correlated for both the bean meal (R(2) = 0.294, p = 0.011) and the fish and bean meal (R(2) = 0.401, p = 0.002).

CONCLUSION

Sous vide cooked salmon fish increases iron absorption from a high phytate bean meal in humans.

The pig as an experimental model for elucidating the mechanisms governing dietary influence on mineral absorption

This review highlights the similarities between pigs and humans and thereby the value of the porcine human nutritional model, and reviews some of the more recent applications of this model for nutritional research.

Chili, but not turmeric, inhibits iron absorption in young women from an iron-fortified composite meal

Chili and turmeric are common spices in indigenous diets in tropical regions. Being rich in phenolic compounds, they would be expected to bind iron (Fe)(3) in the intestine and inhibit Fe absorption in humans. Three experiments were conducted in healthy young women (n = 10/study) to assess the effect of chili and turmeric on Fe absorption from a rice-based meal containing vegetables and iron fortified fish sauce in vivo. Iron absorption was determined by erythrocyte incorporation of stable isotope labels ((57)Fe/(58)Fe) using a randomized crossover design. Addition of freeze-dried chili (4.2 g dry powder, 25 mg polyphenols as gallic acid equivalents) reduced Fe absorption from the meal by 38% (6.0% with chili vs. 9.7% without chili, P = 0.0017). Turmeric (0.5 g dry powder, 50 mg polyphenols as gallic acid equivalents) did not inhibit iron absorption (P = 0.91). A possible effect of chili on gastric acid secretion was indirectly assessed by comparing Fe absorption from acid soluble [(57)Fe]-ferric pyrophosphate relative to water soluble [(58)Fe]-ferrous sulfate from the same meal in the presence and absence of chili. Chili did not enhance gastric acid secretion. Relative Fe bioavailability of ferric pyrophosphate was 5.4% in presence of chili and 6.4% in absence of chili (P = 0.47). Despite the much higher amount of phenolics in the turmeric meal, it did not affect iron absorption. We conclude that both phenol quality and quantity determine the inhibitory effect of phenolic compounds on iron absorption.

Associations of iron status with dietary and other factors in 6-year-old children

OBJECTIVE

To investigate the associations of iron status at 6 years of age with dietary and other factors.

DESIGN

In a cross-sectional study, children's dietary intakes (3-day weighed food record) were recorded, body size was measured and blood samples were taken near their sixth birthday.

SUBJECTS

A sample of 188 children, from two previous studies (cohorts 1 and 2), was contacted, and 139 (74%) agreed to participate.

RESULTS

Multiple regression analyses with dietary and other factors showed that meat and fish consumption, multivitamin/mineral supplement intake (both positively) and cow's milk product consumption (negatively) were associated with log serum ferritin (SF) (adjusted R (2)=0.125; P=0.028; n=129), and juices and residence (rural>urban) with haemoglobin (Hb) (adjusted R (2)=0.085; P=0.034; n=127). Of 21 multivitamin/mineral consumers, none had depleted iron stores compared to 21 iron-depleted of 108 non-consumers (P=0.024). Children living in rural areas (<10,000 inhabitants) (n=33) had higher mean corpuscular volume (MCV) (83.3+/-2.3 fl) than those living in urban areas (>10,000 inhabitants) (82.1+/-3.2 fl; n=103) (P=0.048). Multiple regression analyses with dietary and other factors and growth showed in cohort 1 that residence (rural>urban), weight gain 0-1years (negatively), and meat and fish intake (positively) were associated with Hb (adjusted R (2)=0.323; P=0.030; n=51), meat and fish (positively) with both log SF (adjusted R (2)=0.069; P=0.035; n=52) and MCV (adjusted R (2)=0.064; P=0.035; n=52), and in cohort 2 cow's milk product consumption (negatively) was associated with log SF (adjusted R (2)=0.119; P=0.017; n=41) and residence (rural>urban) with MCV (adjusted R (2)=0.102; P=0.025; n=41).

CONCLUSIONS

Consumption of meat and fish and possibly also juices, as well as multivitamin/mineral intake might affect iron status in 6-year-old children positively, whereas cow's milk product consumption might affect iron status negatively. Slower growth in the first year of life and rural residence are positively related to iron status of 6-year-olds.

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

BACKGROUND

Iron and zinc deficiency remain substantial problems in small children in both developed and developing nations. Optimizing mineral absorption is an important strategy in minimizing this problem.

OBJECTIVES

To assess the effects of beef and soy proteins on the bioavailability of non-heme iron and zinc in children.

METHODS

We measured iron (n = 26) and zinc (n = 36) absorption in 4-8 y old children from meals differing only in protein source (beef or a low-phytate soy protein concentrate). Iron and zinc absorption were measured using multi-tracer stable isotope techniques. Iron absorption was calculated from the red blood cell iron incorporation measured after 14 days and zinc absorption from the ratio of the oral and intravenous excretion of the zinc tracers 48 hours after dosing.

RESULTS

Iron absorption from the beef meal was significantly greater (geometric mean, 7.6%) than from the soy meal (3.5%, p = 0.0015). Zinc absorption from the beef meal was greater (mean +/- SD, 13.7 +/- 6.0%) than from the soy meal (10.1 +/- 4.1%, p = 0.047).

CONCLUSION

These findings indicate that beef protein increases both non-heme iron and zinc absorption compared to soy protein. The effect of protein source on non-heme iron and inorganic zinc absorption should be one of the factors taken into account when designing diets for children. The inhibitory effect of the soy based meal on iron and zinc absorption could be overcome by fortifying the soy protein with these minerals during the production process.

Iron availability: An updated review

Iron is an essential trace element in human nutrition and its deficiency is a world nutritional problem. Due to the high prevalence of anaemia in developing and industrialized countries, it is necessary to maintain a suitable iron intake through diet in order to achieve an appropriate status of this element in the body. For this reason, accurate knowledge of iron availability of foods is essential in order to plan intervention strategies that improve deficient situations of this nutrient. Regarding to the two forms of iron present in foods, heme iron has greater availability than non-heme iron. Beside this, non-heme iron availability is conditioned by several dietary factors, such as classic factors (meat, ascorbic acid, fibre, phytic acid, polyphenols) and new factors (caseinophosphopeptides and fructo-oligosaccharides with prebiotic characteristics). For that reason, the aim of this paper is to accurately review all investigations reported in the past decade related to dietetic factors that influence the bioavailability of different iron forms.

Cultural and environmental barriers to adequate iron intake among northern Kenyan schoolchildren

The purpose of this study was to examine the context of iron deficiency and feeding patterns of iron-rich foods among northern Kenyan school-aged children. A nutrition survey was conducted among 300 subjects in two Rendille communities, Korr and Karare. The objectives were to determine the prevalence of iron deficiency as it relates to parasitic infection, dietary intake, and sociodemographic factors, as well as cultural food proscriptions influencing child feeding. Sociodemographic and qualitative data on food beliefs and child-feeding practices were obtained from the primary caretaker of each subject. From pediatric subjects, 24-hour dietary recall data were obtained with the help of the primary caretaker, and capillary blood from a fingerstick was used to detect iron deficiency based on measures of hemoglobin, the zinc protoporphyrin-to-heme ratio, C-reactive protein, and transferrin receptor. With an overall prevalence of 31.2%, iron deficiency was found to be associated with dietary iron intakes constrained by diverse economic, cultural, and environmental factors among Rendille children. In Karare, where children's iron intake approached recommended levels, iron deficiency was found to be attributable to low bioavailability of iron (only 4.3% of total iron intake), rather than low dietary intake per se. By contrast, in Korr the average daily iron intake was estimated at only 65% of recommended allowances, indicating that iron deficiency was the outcome not merely of low bioavailability, but rather of overall inadequate iron intake. Sociodemographic analysis showed a significant interaction between sex and economic status, revealing that girls in economically sufficient households were 2.4 times as likely to have iron deficiency as boys. This difference in risk parallels culturally defined gender-based proscriptions for child feeding: girls are believed to benefit from "soft foods," including rice, maize porridge, and tea, whereas boys benefitfrom "hard foods," including meat, blood, and beans. Consequently, in households economically able to purchase iron-rich foods, these foods are being preferentially fed to boys. Economic development may result in improved iron status for boys, but it will be unlikely to benefit girls in the absence of a dietary modification intervention. A modification of culturally acceptable "soft foods" to include iron-rich foods may provide a sustainable approach to controlling and preventing iron deficiency in this population.

Participatory nutrition education and adoption of new feeding practices are associated with improved adequacy of complementary diets among rural Malawian children: a pilot study

OBJECTIVE

To introduce practices for improving complementary feeding and evaluate their adoption and association with improved dietary intakes.

DESIGN

A quasiexperimental pilot study comparing dietary intakes from complementary foods among three intervention communities and one control community before and after the intervention, and adoption of new complementary feeding practices among intervention communities following the intervention.

SETTING

Rural subsistence communities in southern Malawi, Central Africa.

SUBJECTS

Mothers and their children aged 6 to 23 months receiving complementary foods.

INTERVENTIONS

A participatory, nutrition education intervention based on four locally adapted lessons for complementary feeding practices designed to increase: (i) total complementary food intake; (ii) energy and nutrient density of the complementary diet, and; (iii) iron and zinc bioavailability of the complementary diet.

RESULTS

Adoption rates for the four practices ranged from 25% for preparation of enriched porridges, to 10% for preparing soaked, pounded maize. The amount of complementary foods (g/day) and intakes of energy, animal protein, niacin, riboflavin, calcium, iron, and zinc, but not vitamin A, were significantly greater (P<0.05) in the intervention compared to control group, as were the energy, iron, and riboflavin density, and the estimated amount of bioavailable iron and zinc.

CONCLUSIONS

Several intervention practices were well accepted and adopted and were associated with improved adequacy of energy and nutrient intakes from the complementary diet. Such improvements were attributed mainly to greater total intakes and, to a lesser extent, enhanced dietary quality of the complementary foods.

Approaches to improve iron bioavailability from complementary foods

The importance of trace element bioavailability in the etiology of nutritional deficiencies, for example in the etiology of iron deficiency and iron deficiency anemia, can be expected to be most pronounced in individuals with high requirements. Of special concern is the situation in poor communities where infants and young children are consuming monotonous, cereal-based diets. Traditionally, cereal-based gruels are often one of the first semisolid foods to be introduced into the infant's diet. These foods can be expected to have low energy and nutrient density as well as low bioavailability of iron due to the presence of phytic acid. Ascorbic acid is a potent enhancer of non-heme iron absorption that can overcome the inhibiting effect of phytic acid when present in high enough quantities. However, home prepared complementary foods based on cereals and legumes contain negligible amounts of ascorbic acid unless ascorbic acid-rich foods are mixed with the cereal or consumed at the same time. Different approaches to improve iron bioavailability from plant-based complementary foods, e.g., by enzymatic degradation of phytic acid and/or by increased consumption of ascorbic acid-rich foods, should be explored and adapted to local conditions. In addition, there is a need to evaluate efficacy and effectiveness of strategies to increase the dietary intake of bioavailable iron by dietary diversification and food fortification under realistic conditions.

Iron status at 12 months of age -- effects of body size, growth and diet in a population with high birth weight

OBJECTIVE

To investigate effects of growth and food intake in infancy on iron status at the age of 12 months in a population with high birth weight and high frequency of breast-feeding.

DESIGN

In a longitudinal observational study infants' consumption and growth were recorded. Weighed 2 day food records at the ages of 6, 9 and 12 months were used to analyse food and nutrient intake.

SETTING

Healthy-born participants were recruited from four maternity wards. Blood samples and growth data were collected from healthcare centres and food consumption data at home.

SUBJECTS

Newborn infants (n=180) were selected randomly according to the mother's domicile and 77% (n=138) participated, of them, 83% (n=114), or 63% of original sample, came in for blood sampling.

RESULTS

Every fifth child was iron-deficient (serum ferritin <12 microg/l and mean corpuscular volume<74 fl) and 2.7% were also anaemic (Hb<105 g/l). Higher weight gain from 0 to 12 months was seen in infants who were iron-deficient at 12 months (6.7+/-0.9 kg) than in non-iron-deficient infants (6.2+/-0.9 kg) (P=0.050). Serum transferrin receptors at 12 months were positively associated with length gain from 0 to 12 months (adjusted r(2)=0.14; P=0.045) and mean corpuscular volume negatively to ponderal index at birth (adjusted r(2)=0.14; P=0.019) and 12 months (adjusted r(2)=0.17; P=0.006). Iron-deficient infants had shorter breast-feeding duration (5.3+/-2.2 months) than non-iron-deficient (7.9+/-3.2 months; P=0.001). Iron status indices were negatively associated with cow's milk consumption at 9-12 months, significant above 460 g/day, but were positively associated with iron-fortified breakfast cereals, fish and meat consumption.

CONCLUSIONS

: In a population of high birth weight, iron deficiency at 12 months is associated with faster growth and shorter breast-feeding duration from 0 to 12 months of age. The results suggest that a diet of 9-12-month-olds should avoid cow's milk above 500 g/day and include fish, meat and iron-fortified breakfast cereals to improve iron status.

The role of meat to improve the critical iron balance during weaning

BACKGROUND

Iron requirements during the weaning period are the highest per unit body weight during human life, and diet is often insufficient to cover iron needs. For the first time in infant nutrition the absorption of both nonheme and heme iron from a typical weaning gruel after addition of meat with and without ascorbic acid (AA) to improve bioavailability was studied.

METHODS

Nonheme and heme iron absorption from gruel was measured in 33 adults using 2 radioiron isotopes--an inorganic iron salt to label nonheme iron, the other biosynthetically labeled rabbit hemoglobin to label heme iron. Iron absorption was measured from the basal gruel (based on milkpowder and cereals) and from basal gruel added 20 g red powdered meat, alone and together with 20 mg AA in 4 different trials.

RESULTS

Nonheme iron absorption from the basal meal was 0.33 mg/1000 kcal and the increase from added 20 mg AA was 39%, whereas addition of red meat increased nonheme iron absorption by 85%. This latter increase was unexpectedly high. Total iron absorption was further increased by heme iron absorption of 0.23 mg Fe/1000 kcal. When adding both meat and AA, total iron absorption amounted to 1.08 mg iron/1000 kcal, ie, exceeding 1 mg/1000 kcal, a level estimated to correspond with daily iron requirements in 95% of infants aged 12 months.

CONCLUSIONS

Addition of powdered red meat to weaning gruels markedly increased total iron absorption. A weaning diet with added powdered meat and AA may serve as a viable option to satisfy the body's high iron requirements during this critical period.

Zinc and breastfed infants: if and when is there a risk of deficiency?

Infancy is a time of relatively high zinc requirements. Human milk provides an excellent source of highly bioavailable zinc and generally meets the needs of the healthy young exclusively breastfed infants for the first several months of life. Investigations of exclusively breastfed infants less than 6 mo of age have generally found zinc homeostasis and status to be adequate, although there are indications that zinc intake from human milk alone may become limiting by around 6 mo of age. Exceptions may be small for gestational age and low birth weight infants, who may well benefit from increased zinc intake before 6 mo of age. The older infant clearly becomes dependent on non-human milk sources of zinc, i.e., from complementary foods. Traditional early complementary foods, such as cereals, fruits, and vegetables provide very modest amounts of zinc, and for those high in phytic acid, bioavailability may be low. Introduction of animal products or zinc supplementation may be important to meet the older infant's zinc requirements This is likely to be particularly important in less protected environments with a high infectious burden and limited dietary options.

Iron bioavailability and weight gains to iron-deficient rats fed a commonly consumed Tunisian meal 'bean seeds ragout' with or without beef and with green or black tea decoction

The Fe bioavailability and the weight gains were evaluated in rats fed a commonly consumed Tunisian meal 'bean seeds ragout' (BSR), with or without beef and with black or green tea decoction. The Fe bioavailability was evaluated in Fe-deficient rats by the hemoglobin repletion method and the Fe stored in the liver. The addition of beef to the BSR significantly increased the Fe bioavailability from this meal by 147% and the reserve of Fe stored in the liver by 77% (P < 0.001). In contrast, both black and green tea decoctions caused a significant decrease of the Fe bioavailability from BSR meal (-19.6 +/- 4.9% and -14.9 +/- 4.1%, respectively). The reserve of Fe stored in the liver was significantly lower in the BSR, the black and the green tea groups than in the positive control group (FeSO4). The weight gains were significantly lower in the black and the green tea groups (3.9 +/- 5.7 g, 13 +/- 1.9 g, respectively) than in the BSR group (24.9 +/- 6 g). The addition of beef to BSR meal counteracted the inhibitory effect of the kidney bean and considerably improved the Fe bioavailability and the Fe stored in the liver of rats. The green tea decoction, which constitutes an important source of antioxidant factors, had the same inhibitory effect as the black tea decoction on the Fe bioavailability from BSR meal. In addition, both black and green teas significantly reduced the weight gains, where the black tea decoction has the most effect.

Nonheme-iron absorption from a phytate-rich meal is increased by the addition of small amounts of pork meat

BACKGROUND

Muscle tissue from various sources is known to promote nonheme-iron absorption. However, systematic studies of the dose dependency of this effect of meat on iron absorption from an inhibitory meal with low amounts of meat are lacking.

OBJECTIVE

We investigated the dose-response effect of small amounts of meat on nonheme-iron absorption from a meal presumed to have low iron bioavailability.

DESIGN

Forty-five healthy women with a mean (+/-SD) age of 24 +/- 3 y were randomly assigned to 1 of 3 groups, each of which was served (A) a basic meal (rice, tomato sauce, pea purée, and a wheat roll) and (B) the basic meal with either 25, 50, or 75 g pork (longissimus muscle). Meal A contained 2.3 mg nonheme iron, 7.4 mg vitamin C, and 220 mg (358 micro mol) phytate. Each meal was served twice, and the order of the meals was ABBA or BAAB. The meals were extrinsically labeled with (55)Fe or (59)Fe. Iron absorption was determined from measurements of (59)Fe whole-body retention and the activity of (55)Fe and (59)Fe in blood samples.

RESULTS

Twenty-five grams meat did not increase nonheme-iron absorption significantly (P = 0.13), whereas absorption increased 44% (P < 0.001) and 57% (P < 0.001), respectively, when 50 and 75 g meat were added to the basic meal. In absolute values, this corresponds to an absorption that was 2.6% and 3.4% higher, respectively, than that with the basic meal after adjustment of the data to a level of 40% absorption from a reference dose.

CONCLUSION

Small amounts of meat (>or=50 g) significantly increase nonheme-iron absorption from a phytate-rich meal low in vitamin C.

Fighting iron deficiency anemia with iron-rich rice

OBJECTIVE

Iron deficiency is estimated to affect about 30% of the world population. Iron supplementation in the form of tablets and food fortification has not been successful in developing countries, and iron deficiency is still the most important deficiency related to malnutrition. Here we present experiments that aim to increase the iron content in rice endosperm and to improve its absorption in the human intestine by means of genetic engineering.

METHODS

We first introduced a ferritin gene from Phaseolus vulgaris into rice grains, increasing their iron content up to twofold. To increase iron bioavailability, we introduced a thermo-tolerant phytase from Aspergillus fumigatus into the rice endosperm. In addition, as cysteine peptides are considered major enhancers of iron absorption, we over-expressed the endogenous cysteine-rich metallothionein-like protein.

RESULTS

The content of cysteine residues increased about sevenfold and the phytase level in the grains about one hundred and thirtyfold, giving a phytase activity sufficient to completely degrade phytic acid in a simulated digestion experiment.

CONCLUSIONS

This rice, with higher iron content, rich in phytase and cysteine-peptide has a great potential to substantially improve iron nutrition in those populations where iron deficiency is so widely spread.

Dietary intakes of 6-24-month-old urban South Island New Zealand children in relation to biochemical iron status

OBJECTIVE

To investigate food sources and intakes of iron, and dietary factors associated with serum ferritin levels in 6-24-month-old children.

DESIGN

A cross-sectional survey employing proportionate cluster sampling was conducted in 1998/1999. Dietary intakes were assessed using a non-consecutive 3-day weighed food record. Serum ferritin and C-reactive protein were analysed from non-fasting venepuncture blood samples and general sociodemographic data were collected.

SETTING

Cities of Christchurch, Dunedin and Invercargill, New Zealand.

SUBJECTS

Randomly selected healthy 6-24-month-old non-breast-feeding children (n = 226).

RESULTS

Total iron intakes (+/- standard deviation (SD)) among non-breast-feeding infants (< 12 months old; n = 42) and toddlers (> or = 12 months old; n = 184) were 8.4 +/- 2.9 mg day(-1) and 5.0 +/- 2.5 mg day(-1), respectively. Fifteen per cent of infants and 66% of toddlers were at risk of inadequate iron intakes. Main sources of dietary iron were infant formula (60%) for infants and cereals (31%) for toddlers. Meat contributed on average 2% and 10% of dietary iron in the infant and toddler diets, respectively. Dietary factors positively associated with serum ferritin were intakes of iron and vitamin C, whereas intakes of calcium and dietary fibre were negatively associated. For each 1% increase in percentage of energy from iron-fortified formula concomitant with a 1% decrease from dairy products, there was a 4.2% increased odds of replete iron stores (ferritin > or = 20 microg l(-1)).

CONCLUSIONS

Toddlers were at higher risk of sub-optimal iron intakes than infants. Results suggest that a diet high in bioavailable iron is important for optimising the iron stores of young children in New Zealand.

Postnatal iron status of Hong Kong Chinese women in a longitudinal study of maternal nutrition

OBJECTIVE

To report postnatal iron nutritional status of Hong Kong Chinese women during the first 6 months postpartum.

DESIGN AND SUBJECTS

A longitudinal study examining postnatal calcium and iron status of Hong Kong Chinese breastfeeding and formula-feeding women was conducted during 1998. Postpartum women aged 20-40 y, with no bone or blood disorders were recruited and interviewed at 0 (baseline), 2, 6 weeks, 3 and 6 months postpartum. Dietary intake was assessed by a 3 day dietary record and cross checked by a 24 h recall. Complete blood count and serum ferritin level were measured to assess anaemia and iron status. In this report, subjects were divided into an anaemic group (haemoglobin level < 10 g/dl) and a non-anaemic group (haemoglobin level > or = 10 g/dl) according to baseline haemoglobin levels.

RESULTS

At baseline, 13/47 (27.7%) subjects were anaemic. Two of these 13 anaemic subjects were still anaemic at 3 and 6 months postpartum. Anaemic subjects showed significantly (P < 0.01) greater amounts of blood loss and a higher rate of primary postpartum haemorrhage than the non-anaemic subjects. Daily food intake and dietary nutrient intake did not differ significantly between the two groups. During the first 6 weeks postpartum, subjects in both groups consumed more poultry and egg, and comparable amounts of meat, compared with women in the Hong Kong general population. Iron and vitamin C intakes for the majority of subjects reached 60% of the US Recommended Daily Allowances. Regression analysis suggested that the rate of change in haemoglobin level in the first 6 weeks postpartum was positively correlated with baseline MCV level and serum ferritin level, but negatively correlated with baseline haemoglobin level.

CONCLUSIONS

Blood loss at delivery is an important factor for postpartum anaemia. Postnatal recovery of iron status of this group of women appeared to be more related to physiological factors than to dietary factors. The role of diet as well as other physiological changes in postpartum women requires further investigation. Finding ways to minimise blood loss at delivery could be the most practical strategy to reduce the rate of postpartum anaemia.

SPONSORSHIP

CSM was supported by a research studentship from the Research Grants Council, Hong Kong.

Iron: deficiencies and requirements

A report from the World Health Organization estimates that 46% of the world's 5- to 14-year-old children are anemic. In addition, 48% of the world's pregnant women are anemic. A majority of these cases of anemia are due to iron deficiency. Our aim here is to review the latest data on iron regulatory mechanisms, iron sources and requirements. Human and animal studies have shown that amino acids and peptides influence iron absorption from the intestinal lumen. Inter-organ transport and uptake of nonheme iron is largely performed by the complex transferring-transferring receptor system. Moreover, the discovery of cytoplasmic iron regulatory proteins (IRPs) has provided a molecular framework from which we understand the coordination of cellular iron homeostasis in mammals. IRPs and the iron responsive elements (IREs) to which they bind allow mammals to make use of the essential properties of iron while reducing its potentially toxic effect. Physiologic iron requirements are three times higher in pregnancy than they are in menstruating women (approximately 1200 mg must be acquired from the body's iron store or from the diet by the end of pregnancy). The administration of iron supplements weekly instead of daily in humans has been proposed and is being actively investigated as a viable means of controlling iron deficiency in populations, including pregnant women.

Bioavailability of dietary supplements and impact of physiologic state: infants, children and adolescents

Bioavailability can be broadly defined as the absorption and utilization of a nutrient, both of which may be affected by such host factors as gender, physiologic state and coexisting pathologic conditions. This report highlights factors of particular importance for the bioavailability of nutrients for infants, children and adolescents. Considerations for nutrient bioavailability for pediatric populations include maturation of the gastrointestinal tract, growth, character of the diet, and nutritional status. Critical periods of development include early infancy (0-6 mo), late infancy/early childhood (6-24 mo) and adolescence (12-18 yr). Iron, zinc and calcium are minerals of particular interest and importance to pediatric populations and are susceptible to alterations in bioavailability. In the young infant, iron and zinc are highly bioavailable from human milk. By approximately 6 mo of age, other dietary sources are needed to maintain continued normal status. In breastfed infants who were born prematurely or with low birth weight, earlier supplemental iron is often recommended. For the older infant and toddler, iron and zinc are also important for normal growth and development. The bioavailability of these trace minerals in complementary foods is discussed. During adolescence, adequate calcium intake is critical to normal bone mineralization. In girls, peak calcium absorption and calcium deposition in bones occur at or near menarche, which illustrates the importance of the physiologic state on mineral bioavailability. Investigations into nutrient bioavailability must carefully consider these factors, because the failure to have well-matched comparison groups with respect to age and/or nutritional status may inadvertently mask differences in nutrient utilization.

Retention of iron by infants

Throughout the world, the most common nutritional deficiency disorder of infants is iron deficiency. Developing effective strategies for preventing iron deficiency requires detailed knowledge of iron retention under ordinary living conditions. For the adult population, such knowledge is at an advanced stage, but relatively little is known about infants. Many reports of iron retention by infants have been based on the assumption that, as in normal and iron-deficient adults, 80%-100% of newly absorbed iron is promptly incorporated into circulating erythrocytes, but this assumption is not supported by available data. This communication presents a review of iron retention by term and preterm infants, as determined by metabolic balance studies or (59)Fe whole-body counting studies, and it explores the relationship between iron retention and postnatal age, iron nutritional status, iron intake (or dose), and type of feeding.

Risk factors for poor iron status in British toddlers: further analysis of data from the National Diet and Nutrition Survey of children aged 1.5-4.5 years

OBJECTIVE

: To examine risk factors for poor iron status in British toddlers.

DESIGN

: National Diet and Nutrition Survey (NDNS) of children aged 1.5-4.5 years.

SETTING

: Mainland Britain, 1992/93.

SUBJECTS

: Of the 1859 children whose parents or guardians were interviewed, a weighed dietary intake was provided for 1675, and a blood sample obtained from 1003.

RESULTS

: Mean haemoglobin (Hb) and ferritin levels were significantly lower in younger (1.5-2.5 years) than in older (3.5-4.5 years) children, with boys having significantly lower ferritin levels than girls. Poor iron status ferritin <10 microg l-1, or low values for both indices) was associated with lower socioeconomic and employment status. Iron status was directly associated with meat and fruit consumption and inversely with that of milk and milk products, after adjustment for age and gender. The latter association remained significant after further adjustment for sociodemographic variables, energy intake and body weight. Children consuming >400 g day-1 of milk and cream were less likely to consume foods in other groups, with those also consuming little meat, fish, fruit and nuts at greatest risk of poor iron status. Few associations were observed between poor iron status and individual nutrient intakes, and iron status was not associated with either iron intake or with consumption of a vegetarian diet.

CONCLUSIONS

: Overdependence on milk, where it displaces iron-rich or iron-enhancing foods, may put toddlers at increased risk of poor iron status. However, this becomes non-significant when moderate-to-high amounts of foods known to enhance iron status (e.g. meat and/or fruit) are also consumed. Milk consumption in this age group should ideally be part of a mixed and balanced diet including all food groups, and particularly lean meat (or other iron-rich or fortified foods) and fruit. This is particularly relevant for households of lower socioeconomic and employment status.

Efficacy of meat and iron-fortified commercial cereal to prevent iron depletion in cow milk-fed infants 6 to 12 months of age: a randomized controlled trial

OBJECTIVE

To determine whether utilization of iron from infant cereal and pureed meat was sufficient to prevent iron depletion and/or anaemia in infants 6 to 12 months old fed whole cow milk (WCM) as their primary milk source.

DESIGN

Six-month-old infants were randomized into a treatment group (n = 43) receiving iron-fortified infant cereal (10.2 mg iron), pureed meat (0.75-1.7 mg iron) and WCM for six months or a control group (n = 54) receiving no dietary intervention. Haemoglobin < 110 g/L or ferritin < 10 micrograms/L (measured bi-monthly), confirmed in a second blood sample, defined end-points.

RESULTS

Proportion reaching end-point was similar between the treatment (3/43) and control infants (5/54) (p = 0.66). Infants not complying with the protocol were at greater risk of reaching end-point (p = 0.0002). Change in haemoglobin and ferritin across age was similar in both groups.

CONCLUSIONS

Iron deficiency is not a concern in WCM-fed infants after six months of age if iron-containing complementary foods are concurrently ingested.

Dietary zinc and iron sources, physical growth and cognitive development of breastfed infants

Iron and zinc are trace minerals that are of critical importance to the young infant for normal growth and development. Exclusive feeding of human milk provides adequate amounts of both of these nutrients for normal term infants for approximately the first 6 mo. of life. Current recommendations for introduction of complementary foods at this age do not emphasize the order of introduction of specific foods because the infant's gastrointestinal tract is considered mature at this time. Consideration of nutritional needs at 6 mo. has generally focused on the increasing risk of iron deficiency the longer the diet is without an additional source of iron. Recently, there has been more recognition of the risk of zinc deficiency in the second half of the first year of life in breastfed infants. Review of common feeding practices indicates that early complementary foods are typically iron fortified but low in zinc. Several studies have now investigated the effects of meat as an earlier complementary food on iron and zinc status. Results of these studies, although requiring further verification, suggest that increased meat intake by breastfed infants >6 mo. old would adequately support both iron and zinc requirements.

Less than 80% of absorbed iron is promptly incorporated into erythrocytes of infants

Erythrocyte incorporation of an administered iron isotope has been used as a surrogate for iron retention on the assumption (validated in normal and iron-deficient adults) that 80-100% of the retained isotope is promptly incorporated into circulating erythrocytes. This assumption has not been validated in infants or children. The purpose of our study was to determine concurrently in normal infants absorption and erythrocyte incorporation of the stable isotope, (58)Fe. In a preliminary study (Study 1), we demonstrated that fecal excretion of ingested isotope occurs predominantly during the first 4 d after administration but continues beyond 7 d after ingestion, that is, beyond the point at which isotope in feces can be explained either by excretion of isotope that failed to enter enterocytes or by exfoliation of isotope-enriched enterocytes. In Study 2, we administered (58)Fe to nine younger (age 20-69 d) and nine older (age 165-215 d) term infants and collected feces for 11 d. Geometric mean retention of (58)Fe by the younger infants was 31.2% of intake at 4 d and 26.9% at 11 d, and by the older infants, 35.0% at 4 d and 32.5% at 11 d. Erythrocyte incorporation of (58)Fe 14 d after ingestion was 5.2% of the dose by the younger infants and 12.5% by the older infants. Utilization of retained (11 d) isotope thus was 19.8% by the younger infants and 38.3% by the older infants. We conclude that far less than 80% of retained isotope is promptly incorporated into erythrocytes (utilized) by infants.