Iron supplementation does not affect copper and zinc absorption in breastfed infants

Evaluating Heavy Metals in Human Breast Milk: a Cross-Sectional Study from Mining and Agricultural Areas in Northwestern Iran

This study aimed to assess the levels of heavy metals in the breast milk of women residing in the mining and agricultural areas of East Azerbaijan province in Iran. This cross-sectional study analyzed 68 lactating mothers from mining (n = 28) and agricultural (n = 40) areas of East Azerbaijan province in Iran between June 2022 and March 2023. The study used an Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) to measure the concentrations of heavy metals, including arsenic (As), chromium (Cr), copper (Cu), and iron (Fe). A semi-quantitative food frequency questionnaire (SQ-FFQ) was used to collect data on the dietary and sociodemographic characteristics of the mothers. Although the concentration of arsenic (As) was below the limit of detection (LOD), the mean concentrations of chromium (Cr), copper (Cu), and iron (Fe) were 1.11, 0.87, and 13.25 mg/L in agricultural areas and 0.83, 0.93, and 11.35 mg/L in mining areas, respectively. The concentrations of Cr (p < 0.001) and Fe (p = 0.019) were significantly higher in the breast milk of women residing in agricultural areas. However, the concentration of Cu was significantly higher (p = 0.085) in the breast milk of women living in mining areas. Additionally, lactation age had a significant effect on Cu levels (p = 0.015), with a negative coefficient of -0.011. The study indicates that the levels of heavy metals in breast milk can be influenced by the exposure to pesticides, fertilizers, volcanic soil, and disparities in access to post-natal care and iron supplements.

Scientific opinion on the tolerable upper intake level for iron

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the tolerable upper intake level (UL) for iron. Systematic reviews were conducted to identify evidence regarding high iron intakes and risk of chronic diseases, adverse gastrointestinal effects and adverse effects of iron supplementation in infancy, young childhood and pregnancy. It is established that systemic iron overload leads to organ toxicity, but no UL could be established. The only indicator for which a dose-response could be established was black stools, which reflect the presence of large amounts of unabsorbed iron in the gut. This is a conservative endpoint among the chain of events that may lead to systemic iron overload but is not adverse per se. Based on interventions in which black stools did not occur at supplemental iron intakes of 20-25 mg/day (added to a background intake of 15 mg/day), a safe level of intake for iron of 40 mg/day for adults (including pregnant and lactating women) was established. Using allometric scaling (body weight0.75), this value was scaled down to children and adolescents and safe levels of intakes between 10 mg/day (1-3 years) and 35 mg/day (15-17 years) were derived. For infants 7-11 months of age who have a higher iron requirement than young children, allometric scaling was applied to the supplemental iron intakes (i.e. 25 mg/day) and resulted in a safe level of supplemental iron intake of 5 mg/day. This value was extended to 4-6 month-old infants and refers to iron intakes from fortified foods and food supplements, not from infant and follow-on formulae. The application of the safe level of intake is more limited than a UL because the intake level at which the risk of adverse effects starts to increase is not defined.

Iron Fortification and Inulin Supplementation in Early Infancy: Evaluating the Impact on Iron Metabolism and Trace Mineral Status in a Piglet Model

Background

Infant formula in the United States contains abundant iron, raising health concerns about excess iron intake in early infancy.

Objectives

Using a piglet model, we explored the impact of high iron fortification and prebiotic or synbiotic supplementation on iron homeostasis and trace mineral bioavailability.

Methods

Twenty-four piglets were stratified and randomly assigned to treatments on postnatal day 2. Piglets were individually housed and received an iron-adequate milk diet (AI), a high-iron milk diet (HI), HI supplemented with 5% inulin (HI with a prebiotic [HIP]), or HIP with an oral gavage of Ligilactobacillus agilis YZ050, an inulin-fermenting strain, every third day (HI with synbiotic [HIS]). Milk was provided in 14 meals daily, mimicking formula feeding in infants. Fecal consistency score and body weight were recorded daily or every other day. Blood and feces were sampled weekly, and tissues collected on postnatal day 29. Data were analyzed using mixed model analysis of variance with repeated measures whenever necessary.

Results

Diet did not affect growth. HI increased hemoglobin, hematocrit, and serum iron compared to AI. Despite marginal adequacy, AI upregulated iron transporter genes and maintained satisfactory iron status in most pigs. HI upregulated hepcidin gene expression in liver, caused pronounced tissue iron deposition, and markedly increased colonic and fecal iron. Inulin supplementation, regardless of L. agilis YZ050, not only attenuated hepatic iron overload but also decreased colonic and fecal iron without altering pH or the expression of iron regulatory genes. HI lowered zinc (Zn) and copper (Cu) in the duodenum and liver compared to AI, whereas HIP and HIS further decreased Zn and Cu in the liver and diminished colonic and fecal trace minerals.

Conclusions

Early-infancy excessive iron fortification causes iron overload and compromises Zn and Cu absorption. Inulin decreases trace mineral absorption likely by enhancing gut peristalsis and stool frequency.

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.

Sources and levels of copper affect liver copper profile, intestinal morphology and cecal microbiota population of broiler chickens fed wheat-soybean meal diets

Super dosing copper (Cu) has long been used as an alternative to antibiotic growth-promoters in broiler chickens' diet to improve gut health. This study was designed to compare nutritional and growth-promoting levels of Cu hydroxychloride (CH) with CuSO4 on gut health bio-markers and liver mineral profile of broiler chickens. Ross 308 chicks (n = 864) were randomly assigned to eight treatments, as basal diet containing no supplemental Cu; the basal diet with 15 or 200 mg/kg Cu as CuSO4; or 15, 50, 100, 150 or 200 mg/kg Cu from CH. The highest liver Cu content was observed in birds fed the diets with 200 mg/kg CuSO4 (P < 0.01). Serum FITC-d concentration as the leaky gut marker, and liver malondialdehyde concentration were not affected. Copper level or source had no effect on cecal short chain fatty acid and the mRNA expression of five jejunal genes involved in gut integrity. Negative linear responses of Cu were observed on Lactobacillus (P = 0.032), Bacteroides (P = 0.033), and Enterobacteriaceae (P = 0.028) counts. The jejunal villus height increased in birds fed CH at 200 and 100 mg/kg (P < 0.05). Increasing Cu levels, linearly and quadratically (P < 0.001), increased Cu excretion.

The Benefits and Risks of Iron Supplementation in Pregnancy and Childhood

Iron deficiency is the most common micronutrient deficiency in the world and disproportionately affects pregnant women and young children. Iron deficiency has negative effects on pregnancy outcomes in women and on immune function and neurodevelopment in children. Iron supplementation programs have been successful in reducing this health burden. However, iron supplementation of iron-sufficient individuals is likely not necessary and may carry health risks for iron-sufficient and potentially some iron-deficient populations. This review considers the physiology of iron as a nutrient and how this physiology informs decision-making about weighing the benefits and risks of iron supplementation in iron-deficient, iron-sufficient, and iron-overloaded pregnant women and children.

Dietary copper restriction in Wilson's disease

Dietary copper restriction has long been considered an important aspect of treatment for Wilson's disease (WD). However, evidence supporting this approach is limited. There are no published randomised controlled trials examining this recommendation due to rarity of the disease and variable presentation. This review summarises current knowledge on the absorption and regulation of copper in humans and its relevance to patients with WD. Studies have demonstrated that as the level of dietary copper increases, the proportion absorbed decreases. This observation implies that 'high copper' foods that WD patients are generally advised to avoid would need to be consumed in large amounts to impact markedly on the quantity absorbed. Dietary copper restriction is unlikely to reduce the amount absorbed significantly and is not only difficult to manage but restricts food groups unnecessarily, detracting from the provision of substrates essential for improving nutritional status in a nutritionally compromised group. Medical management for WD is effective in compliant patients, allowing stabilisation of the liver disease. Based on current evidence, dietary copper restrictions in stable WD patients who are adherent to medical therapy are unnecessary with two food exceptions (shellfish and liver).

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.

Intakes of Micronutrients Are Associated With Early Growth in Extremely Preterm Infants

OBJECTIVES

The aim of the study was to describe micronutrient intakes and explore possible correlations to growth during the first 70 days of life in extremely preterm infants.

METHODS

Retrospective population-based study including extremely preterm infants (<27 weeks) born in Sweden during 2004-2007. Detailed nutritional and growth data were derived from hospital records.

RESULTS

Included infants (n = 531) had a mean gestational age of 25 weeks and 2 days and a mean birth weight of 765 g. Estimated and adjusted intakes of calcium, phosphorus magnesium, zinc, copper, selenium, vitamin D, and folate were lower than estimated requirements, whereas intakes of iron, vitamin K, and several water-soluble vitamins were higher than estimated requirements. High iron intakes were explained by blood transfusions. During the first 70 days of life, taking macronutrient intakes and severity of illness into account, folate intakes were positively associated with weight (P = 0.001) and length gain (P = 0.003) and iron intake was negatively associated with length gain (P = 0.006).

CONCLUSIONS

Intakes of several micronutrients were inconsistent with recommendations. Even when considering macronutrient intakes and severity of illness, several micronutrients were independent predictors of early growth. Low intake of folate was associated with poor weight and length gain. Furthermore, high iron supply was associated with poor growth in length and head circumference. Optimized early micronutrient supply may improve early growth in extremely preterm infants.

Effect of dietary copper amount and source on copper metabolism and oxidative stress of weanling pigs in short-term feeding

Forty-eight weanling barrows were used to determine the effects of amount and source of dietary Cu on Cu metabolism, oxidative stress in the duodenum, and VFA ratios in the cecum of weanling pigs in short-term feeding. At 21 d of age, newly weaned pigs were stratified by BW (7.03 ± 1.20 kg) and equally assigned to 1 of the following dietary treatments: 1) control (5 mg supplemental Cu/kg diet from CuSO4), 2) 225 mg supplemental Cu/kg diet from CuSO4, or 3) 225 mg supplemental Cu/kg diet from tribasic Cu chloride (TBCC). Pigs were housed 2 pigs per pen and were fed a complex diet until harvest on d 11 and 12. During harvest, bile and liver were obtained for mineral analysis, and liver samples were obtained for analysis of mRNA expression of Cu regulatory proteins. Digesta of duodenum, proximal jejunum, and ileum were collected for soluble Cu analysis. Mucosal scrapings of duodenum, proximal jejunum, and ileum were obtained for analysis of mucosal Cu concentration and mRNA expression of Cu regulatory proteins. Duodenal mucosal scrapings were also collected for analysis of malondialdehyde (MDA). Pigs fed high Cu had markedly greater (P < 0.0001) Cu concentrations in the duodenal, proximal jejunal, and ileal mucosa than controls. Copper in the duodenal mucosa was greater (P = 0.003) in CuSO4 than TBCC pigs. Duodenal MDA concentrations were greater (P = 0.003) in CuSO4 vs. control pigs and tended (P = 0.06) to be greater than in TBCC pigs. Duodenal antioxidant 1 (Atox1) mRNA was downregulated (P < 0.01) in pigs fed high Cu compared to controls and was not affected by Cu source. Compared with control pigs, those fed CuSO4 and TBCC had greater (P < 0.001) liver and bile Cu concentrations. Liver Cu was also greater (P = 0.0007) in TBCC than CuSO4-fed pigs. Hepatic Cu transporting β-polypeptide ATPase (Atp7b) was upregulated (P = 0.02) in the Cu-supplemented pigs compared with controls and did not differ among Cu sources. The acetate:propionate ratio in cecal contents was much greater in pigs supplemented with 225 mg Cu/kg diet than in controls. When fed at 225 mg Cu/kg diet, TBCC may cause less oxidative stress in the duodenum than CuSO4. Feeding weanling pigs increased Cu resulted in modulation of duodenal and liver at the transcription level.

The association between content of the elements S, Cl, K, Fe, Cu, Zn and Br in normal and cirrhotic liver tissue from Danes and Greenlandic Inuit examined by dual hierarchical clustering analysis

PROJECT

Meta-analysis of previous studies evaluating associations between content of elements sulphur (S), chlorine (Cl), potassium (K), iron (Fe), copper (Cu), zinc (Zn) and bromine (Br) in normal and cirrhotic autopsy liver tissue samples.

PROCEDURE

Normal liver samples from 45 Greenlandic Inuit, median age 60 years and from 71 Danes, median age 61 years. Cirrhotic liver samples from 27 Danes, median age 71 years. Element content was measured using X-ray fluorescence spectrometry.

STATISTICS

Dual hierarchical clustering analysis, creating a dual dendrogram, one clustering element contents according to calculated similarities, one clustering elements according to correlation coefficients between the element contents, both using Euclidian distance and Ward Procedure.

RESULTS

One dendrogram separated subjects in 7 clusters showing no differences in ethnicity, gender or age. The analysis discriminated between elements in normal and cirrhotic livers. The other dendrogram clustered elements in four clusters: sulphur and chlorine; copper and bromine; potassium and zinc; iron. There were significant correlations between the elements in normal liver samples: S was associated with Cl, K, Br and Zn; Cl with S and Br; K with S, Br and Zn; Cu with Br. Zn with S and K. Br with S, Cl, K and Cu. Fe did not show significant associations with any other element.

CONCLUSIONS

In contrast to simple statistical methods, which analyses content of elements separately one by one, dual hierarchical clustering analysis incorporates all elements at the same time and can be used to examine the linkage and interplay between multiple elements in tissue samples.

Health effects of different dietary iron intakes: a systematic literature review for the 5th Nordic Nutrition Recommendations

BACKGROUND

The present literature review is part of the NNR5 project with the aim of reviewing and updating the scientific basis of the 4th edition of the Nordic Nutrition Recommendations (NNR) issued in 2004.

OBJECTIVE

The objective of this systematic literature review was to assess the health effects of different intakes of iron, at different life stages (infants, children, adolescents, adults, elderly, and during pregnancy and lactation), in order to estimate the requirement for adequate growth, development, and maintenance of health.

METHODS

The initial literature search resulted in 1,076 abstracts. Out of those, 276 papers were identified as potentially relevant. Of those, 49 were considered relevant and were quality assessed (A, B, or C). An additional search on iron and diabetes yielded six articles that were quality assessed. Thus, a total of 55 articles were evaluated. The grade of evidence was classified as convincing (grade 1), probable (grade 2), suggestive (grade 3), and inconclusive (grade 4).

RESULTS

There is suggestive evidence that prevention or treatment of iron deficiency (ID) and iron deficiency anemia (IDA) improves cognitive, motoric, and behavioral development in young children, and that treatment of IDA improves attention and concentration in school children and adult women. There is insufficient evidence to show negative health effects of iron intakes in doses suggested by the NNR 4. There is insufficient evidence to suggest that normal birth weight, healthy, exclusively breast-fed infants need additional dietary iron before 6 months of life in the Nordic countries. An iron concentration of 4-8 mg/L in infant formulas seems to be safe and effective for normal birth weight infants. There is probable evidence that iron supplements (1-2 mg/kg/day) given up to 6 months of age to infants with low birth weight (<2,500 g) prevents IDA and possibly reduce the risk of behavioral problems later on. There is probable evidence that ID and IDA in pregnant women can be effectively prevented by iron supplementation at a dose of 40 mg/day from week 18-20 of gestation. There is probable evidence that a high intake of heme iron, but not total dietary, non-heme or supplemental iron, is associated with increased risk of type 2 diabetes (T2D) and gestational diabetes.

CONCLUSIONS

Overall, the evidence does not support a change of the iron intakes recommended in the NNR 4. However, one could consider adding recommendations for infants below 6 months of age, low birth weight infants and pregnant women.

Iron supplementation in pregnancy and breastfeeding and iron, copper and zinc status of lactating women from a human milk bank

This study evaluated the influence of iron supplementation in pregnancy and breastfeeding on iron status of lactating women from a Brazilian Human Milk Bank. Blood and mature breast milk samples were collected from 145 women for assessment of iron status, as well as copper and zinc status. Haemoglobin, serum iron and ferritin were determined, respectively, by electronic counting, colorimetry and chemiluminescence. Transferrin and ceruloplasmin were analysed by nephelometry. Serum copper and zinc were measured by atomic absorption spectrophotometry, and serum alkaline phosphatase was measured by a colorimetric method. Iron, zinc and copper in breast milk were determined by spectrometry. Mean values of iron, copper and zinc (blood and breast milk) were compared by ANOVA, followed by Tukey's test. Iron supplementation was beneficial to prevent anaemia in pregnancy but not effective to treat anaemia. During breastfeeding, iron supplementation had a negative effect on maternal copper status, confirming an interaction between these micronutrients.

Development of nutritional iron deficiency in growing male rats: haematological parameters, iron bioavailability and oxidative defence

Despite Fe deficiency having been widely studied, the sequence of events in its development still remains unclear. The aim of the present study was to elucidate the effects of nutritional Fe-deficiency development on haematological parameters, Fe bioavailability and the enzymes involved in oxidative defence in recently weaned male Wistar albino rats. Control (C) and Fe-deficient (ID) groups were fed the AIN-93 G diet with a normal Fe level (45 mg/kg diet) or with a low Fe level (5 mg/kg diet), respectively, for 20, 30 or 40 d. At day 20 serum Fe, serum ferritin and the saturation of transferrin decreased drastically, decreasing further in the course of Fe-deficiency development for the saturation of transferrin. The development of Fe deficiency did not affect plasma thiobarbituric acid-reactive substance production, or catalase (CAT) and glutathione peroxidase (GPx) activities in erythrocyte cytosol. Fe deficiency diminished hepatic Fe content and CAT and GPx activities in hepatic cytosol only at day the 20. However, in spite of the minor Fe deposits in the brain of ID rats, the CAT and GPx activities in the brain cytosolic fraction did not differ in any of the studied periods v. control rats. These results show that brain is a tissue that does not seem to depend on Fe levels for the maintenance of antioxidant defence mechanisms in the course of nutritional Fe deficiency.