Iron absorption in breast-fed infants: effects of age,iron status,iron supplements,and complementary foods

BACKGROUND: Iron supplements are often recommended for older breast-fed infants, but little is known about factors affecting iron absorption from human milk or supplements. OBJECTIVE: We investigated the effects of age, iron status, and iron intake on iron absorption in healthy, term, breast-fed infants. DESIGN: Twenty-five infants were randomly assigned to receive either 1) iron supplements (1 mg x kg(-1) x d(-1)) from 4 to 9 mo of age, 2) placebo from 4 to 6 mo and iron supplements from 6 to 9 mo, or 3) placebo from 4 to 9 mo. Infants were exclusively breast-fed to 6 mo and partially breast-fed to 9 mo of age. Iron absorption was assessed by giving (58)Fe with mother's milk at 6 and 9 mo. Blood samples were obtained at 4, 6, and 9 mo, and complementary food intake was recorded at 9 mo. RESULTS: At 6 mo, mean (+/-SD) fractional iron absorption from human milk was relatively low (16.4 +/- 11.4%), with no significant difference between iron-supplemented and unsupplemented infants. At 9 mo, iron absorption from human milk remained low in iron-supplemented infants (16.9 +/- 9.3%) but was higher (P = 0.01) in unsupplemented infants (36.7 +/- 18.9%). Unexpectedly, iron absorption at 9 mo was not correlated with iron status but was significantly correlated with intake of dietary iron, including supplemental iron. CONCLUSIONS: Changes in the regulation of iron absorption between 6 and 9 mo enhance the infant's ability to adapt to a low-iron diet and provide a mechanism by which some, but not all, infants avoid iron deficiency despite low iron intakes in late infancy.     

Haemoglobin fortified cereal: a source of available iron to breast-fed infants

We tested in the field an extruded rice flour, fortified with a bovine haemoglobin concentrate (Fe:14 mg/100 g of powder). This cereal has a high iron bioavailability, good protein quality and amino acid score. Healthy, term breast-fed infants were prospectively studied. One group (n = 92) received the fortified cereal (from 4 to 12 months of age). As control, 96 infants received regular solid foods (cooked vegetables and meat) from age 4 months. At the end of the field trial, a subsample of infants in both groups was supplemented with 45 mg Fe during 90 d. Iron nutrition status was determined at 9, 12 and 15 months. At 12 months, iron deficiency anaemia was present in 17 per cent of controls, in 10 per cent of fortified infants as a whole, but only in 6 per cent of the babies who consumed over 30 g of cereal/d. In addition, this latter group did not show any significant changes in iron nutrition status after the supplementation trial. Results demonstrate that the consumption of a haemoglobin fortified cereal is effective in markedly reducing the incidence of iron deficiency in breast-fed infants.     

Mineral composition and zinc metabolism in female mice of varying age and reproductive status

Zinc metabolism of adult female C57BL/6J mice varying in age and reproductive status was studied using 65Zn. Animals were injected intraperitoneally with isotope, and whole-body and tissue turnover of 65Zn was measured. Biological half-life of whole-body 65Zn for pregnant females was 129% of that for nonpregnant, nonlactating females of similar age (25.7 and 20.0 d, respectively). Conversely, the half-life of zinc was less for lactating (11.1 d) and aged (15.3 d) females than for either pregnant or nonpregnant, nonlactating young adult females. Retention of 65Zn was generally lower for all tissues of pregnant and lactating dams than for nonpregnant, nonlactating females except for brain and tibia. In aged females, specific activity at 20 d postinjection did not differ from that of nonpregnant, nonlactating young adult females for any tissue except bone. While specific activity of tibia increased during pregnancy and lactation, it was lower in aged females than in nonpregnant, nonlactating young adult females. Increased organ content of zinc resulted from changes in zinc concentration or in organ mass or both, and was supported by increased food intake. Thus, greater food intake for these groups than for young adult females contributed to the higher turnover of tissue 65Zn. Differences in concentrations of Cu, Ca and Mg were also observed among groups for some tissues; the significance of these differences and their relationship to zinc metabolism are not clear.     

Copper, iron, zinc, and selenium dietary intake and status of Nepalese lactating women and their breast-fed infants

The dietary intake of copper, iron, zinc, and selenium of 26 Nepalese lactating mothers was estimated from chemical analysis of 24-h food and beverage composites. Fasting blood and milk samples were obtained from the mothers and blood samples were obtained from the infants. The Nepalese mothers consumed significantly more Cu, significantly less Fe and Se, and similar amounts of Zn as compared with American lactating women. Blood Fe status indices and plasma concentrations of Cu, Zn, and Se were lower in the Nepalese mothers than in the American mothers. These lower values may in part be related to the high neutral detergent fiber and phytate content of the Nepalese diet, which could make these minerals less available for absorption. The high exposure to infections in Nepal may also depress Fe status indices and plasma Zn concentrations. The lower dietary Se intake of the Nepalese mothers was reflected in lower milk concentrations.     

Predictors of micronutrient status among six- to twelve-month-old breast-fed Ghanaian infants

This study describes the factors associated with hemoglobin and plasma ferritin, zinc and retinol concentrations and erythrocyte riboflavin status among 208 Ghanaian infants who participated in a complementary feeding intervention trial from 6 to 12 mo of age. Anthropometric, morbidity and dietary data were collected regularly from 1 to 12 mo; blood samples were collected at 6 and 12 mo. The prevalence of low micronutrient status at 6 and 12 mo, respectively, was as follows: hemoglobin <100 g/L, 30 and 34%; plasma ferritin <12 microg/L, 17 and 43%; plasma zinc <10.7 micromol/L, 4 and 6%; plasma retinol <0.7 micromol/L, 26 and 26%; erythrocyte riboflavin <200 umol/L of packed red cells, 14 and 10%. Multiple regression was used to identify factors significantly associated with micronutrient status. From 6 to 12 mo, fever prevalence was associated with a decrease in hemoglobin, but an increase in erythrocyte riboflavin concentrations, and diarrhea prevalence was related to a decrease in plasma retinol. Seasonal differences were evident for most of the indicators of micronutrient status, and elevated C-reactive protein levels (indicative of recent infection) were related to lower hemoglobin, retinol and zinc concentrations but higher ferritin and erythrocyte riboflavin concentrations. Weight at birth or at 1 mo of age was positively related to iron, zinc and vitamin A status, but a more rapid weight gain was associated with depletion of iron stores. Socioeconomic status was related to higher hemoglobin, riboflavin and zinc concentrations. The feeding of a micronutrient-fortified food was positively associated with plasma ferritin and retinol concentrations at 12 mo. These results suggest that prenatal factors, socioeconomic status, dietary intake and morbidity all influence infant micronutrient status, and that fortification of complementary foods is one potential avenue for preventing deficiencies.     

Chromium picolinate supplementation in women: effects on body weight, composition, and iron status

OBJECTIVE: This study tested the hypothesis that supplementation of chromium picolinate (CrPic), 200 microg Cr/d, compared with an equivalent amount of picolinic acid (1720 microg) in CrPic and placebo, decreases body weight, alters body composition, and reduces iron status of women fed diets of constant energy and nutrients. METHODS: We fed 83 women nutritionally balanced diets, used anthropometry and dual x-ray absorptiometry to assess body composition, and measured serum and urinary Cr and biochemical indicators of iron status before and serially every 4 wk for 12 wk in a double-blind, randomized trial. RESULTS: CrPic supplementation increased (P < 0.0001) serum Cr concentration and urinary Cr excretion compared with picolinic acid and placebo. CrPic did not affect body weight or fat, although all groups lost (P < 0.05) weight and fat; it did not affect fat-free, mineral-free mass or measurements of iron status. CONCLUSION: Under conditions of controlled energy intake, CrPic supplementation of women did not independently influence body weight or composition or iron status. Thus, claims that supplementation of 200 microg of Cr as CrPic promotes weight loss and body composition changes are not supported.     

Energy requirements of breast-fed infants

Current recommendations for energy intake are reviewed in light of emerging data on energy intakes of breast-fed infants and on total daily energy expenditure of infants. For determination of energy requirements, the historical approach based on observed intakes of healthy infants is compared with a newly proposed approach based on energy expenditure and deposition. A data set of exclusively breast-fed infants is used to illustrate the circuity of either approach. Energy intake, expenditure, and stores must be evaluated in an assessment of dietary adequacy. Ultimately, energy requirements of infants should reflect growth rate, body composition, and level of physical activity conducive to optimal health and neurobehavioral development.     

4月龄和6月龄婴儿铁营养状况指标的性别差异研究

目的比较4、6月龄母乳喂养婴儿各铁状况指标的性别差异。方法在北京某医院征集铁营养状况正常、足月妊娠的孕妇,选择正常出生体重的足月婴儿并要求婴儿在4月龄内基本纯母乳喂养。在4月龄时将追踪到的婴儿随机分成对照组和补铁组,补铁组婴儿进行为期2个月的预防性铁补充(补铁剂量为每日1mg/kg),对照组婴儿不予干预。4月和6月龄时,采集静脉血测定血常规及其他各项铁营养状况指标并测量其生长发育各项指标。结果追踪结束后,4、6月龄时完成随访的婴儿分别有178例、85例。4月龄时男婴的Hb水平比女婴低1g/L,但无统计学差异(P=0.422)。男婴的MCV值、SF值均低于女婴,sTfR值高于女婴,三个指标的性别间差异具有统计学意义。6月龄时各指标结果保持了4月时的差异趋势,MCV的性别差异具有统计学意义。结论 4月龄和6月龄男婴患铁缺乏的风险更大,需要针对不同性别制定各铁营养状况指标的诊断界值和膳食铁需要量,同时注意科学喂养。     

Energy utilization of breast-fed and formula-fed infants

Breast-fed and formula-fed infants (n = 65) were studied at 1 and 4 mo of age to elucidate differences in energy utilization between feeding groups. Gross energy intake at 1 mo was comparable between groups but was statistically different at 4 mo. Weight, length, and weight gain were not different between groups. Energy expenditure 0-4 h postprandially did not differ between feeding groups. Sleeping metabolic rates (SMRs) were not different but minimal observable energy expenditures standardized by weight were lower among 4-mo-old breast-fed infants (p less than 0.03). No differences were found between feeding groups in thermic effect of feeding (TEF). Activity patterns revealed that breast-fed infants slept less than formula-fed infants (p less than 0.04). Disparities in energy intake observed between breast-fed and formula-fed infants at 4 mo of age did not result in statistically significant differences in growth rate, SMR, or TEF.     

Iron deficiency, but not anemia, upregulates iron absorption in breast-fed peruvian infants

Iron absorption in adults is regulated by homeostatic mechanisms that decrease absorption when iron status is high. There are few data, however, regarding the existence of a similar homeostatic regulation in infants. We studied 2 groups of human milk-fed infants using (57)Fe (given as ferrous sulfate without any milk) and (58)Fe (given at the time of a breast-milk feeding) stable isotopes to determine whether healthy infants at risk for iron deficiency would regulate their iron absorption based on their iron status. We studied 20 Peruvian infants at 5-6 mo of age and 18 infants at 9-10 mo of age. We found no effect of infant hemoglobin concentration on iron absorption with 5-6 mo-old infants absorbing 19.2 +/- 2.1% and 9- to 10-mo-old infants absorbing 25.8 +/- 2.6% of the (57)Fe dose. For (58)Fe, 5- to 6-mo-old infants absorbed 42.6 +/- 5.0% and 9 to 10-mo-old infants absorbed 51.9 +/- 10.3%. Following log transformation, iron absorption from (57)Fe (r = -0.61, P = < 0.001) and (58)Fe (r = -0.61, P = < 0.001) were inversely correlated to serum ferritin (S-Ft). For both the (57)Fe and (58)Fe doses, infants with S-Ft <12 mg/L (n = 11) had significantly higher iron absorption than those with S-Ft >12 mg/L. We concluded that iron absorption in infants is related to iron status as assessed by serum ferritin but not hemoglobin concentration. Infants with low iron status upregulate iron absorption from breast milk at both 5-6 and 9-10 mo of age.     

婴幼儿铁营养现状及其影响

铁缺乏是遍及全球的营养缺乏性公共卫生问题,生长发育迅速的婴幼儿尤为突出.铁缺乏可对婴幼儿造成多方面的不良影响,有些表现为不可逆损害.该文从影响铁营养状况的体外宏观角度和体内微观角度进行综述,探讨影响铁生物利用率的多层面因素,以期在人类发展的关键阶段--婴幼儿期,有效地预防铁缺乏,促进婴幼儿体格和智能发育.     

Zinc and iron status and growth in healthy infants

OBJECTIVE: To elucidate the relationships between growth and zinc and iron status in normal infants. STUDY DESIGN: Growth of normal infants (less than 3 y old: n = 66) was prospectively assessed with a mean delay of 24+/-6 weeks between measurements; subjects were free from illness and presented with a normal growth. Growth was compared to serum zinc (s-zinc), IGF-1 and iron status. SETTING: Teaching hospital of Caen. RESULTS: No relation was found between linear or weight growth and s-zinc; when taking into account the effect of age, linear growth was significantly associated with ferritin (P<0.001); weight gain was significantly correlated with IGF-1 (P = 0.034) and ferritin (P = 0.008). No relationship was found between s-zinc and iron status. CONCLUSIONS: In normal infants iron status, more than serum zinc, seems to be correlated with growth.     

Zinc requirements and zinc intakes of breast-fed infants

Longitudinal changes in dietary zinc requirements for infants at different levels of net absorption were estimated using a factorial approach. Apart from variations in net absorption, the zinc needed for new lean body mass is the major determinant of requirements. As growth velocity declines progressively, estimated zinc requirements for growth and for replacement of urine and sweat losses decrease from a high for male infants of 780 micrograms/day at 1 mo to 480 micrograms/day in the 5th mo and then remain quite constant through the 1st yr. Calculated percentage absorption of zinc from human milk necessary to meet estimated requirements increases with duration of lactation. For infants of mothers whose zinc intake approximated 25 mg/day the calculated percentage absorption remained within plausible limits. It is suggested that the progressive decrease in milk zinc concentrations provides a mechanism for conserving maternal zinc while meeting infant needs.     

Macro- and trace-mineral intakes of exclusively breast-fed infants

Intakes of calcium, phosphorus, magnesium, zinc, sodium, potassium, iron, and copper of 45 exclusively breast-fed infants were determined during the first 4 mo of life. Direct 24-h measurements of milk intake and mineral contents of human milk were used to estimate mineral intakes. Daily intakes of Ca, P, Zn, K, Na, Fe, and Cu decreased significantly over the study period while the intake of Mg increased. With the exception of Mg, mineral intakes on a weight basis displayed significant quadratic trends over the 4 mo. In spite of seemingly low-mineral intakes, growth progressed satisfactorily.     

Vitamin B6 status of breast-fed infants in relation to pyridoxine HCl supplementation of mothers

The vitamin B6 nutritue of breast-fed infants was evaluated by vitamin B6 intake, plasma pyridoxal 5'-phosphate (PLP) concentration, and growth patterns during the infants' first 6 mo of age. Vitamin B6 intakes of 47 healthy, term infants were significantly correlated with four levels of maternal vitamin B6 supplements: 2.5, 4.0, 7.5, or 10.0 mg pyridoxine (PN) HCl/d and met the B6 Adequate Intake (AI, 1998) of 0.1 mg/d for infants 0 to 6 mo. Only infants whose mothers received 10.0 mg PN x HCl/d exceeded or met the Recommended Dietary Allowances (RDA, 1989) of 0.3 mg vitamin B6/d from 4 to 6 mo of age. Plasma PLP concentrations of infants, measured at 1, 4, and 6 mo of age paralleled their mother's vitamin B6 intake. Most infants showed normal growth. The findings indicated that a maternal PN x HCl supplement of 2.5 mg/d provided an adequate amount of vitamin B6 in breast milk (0.15 mg/d) for the vitamin B6 status parameters and the growth of breast-fed infants.     

Dry cereals fortified with electrolytic iron or ferrous fumarate are equally effective in breast-fed infants

Precooked, instant (dry) infant cereals in the US are fortified with electrolytic iron, a source of low reactivity and suspected low bioavailability. Iron from ferrous fumarate is presumed to be more available. In this study, we compared a dry infant rice cereal (Cereal L) fortified with electrolytic iron (54.5 mg iron/100 g cereal) to a similar cereal (Cereal M) fortified with ferrous fumarate (52.2 mg Fe/100 g) for efficacy in maintaining iron status and preventing iron deficiency (ID) in breast-fed infants. Ascorbic acid was included in both cereals. In this prospective, randomized double-blind trial, exclusively breast-fed infants were enrolled at 1 mo and iron status was determined periodically. At 4 mo, 3 infants had ID anemia and were excluded. Ninety-five infants were randomized at 4 mo, and 69 (36 Cereal L, 33 Cereal M) completed the intervention at 9 mo. From 4 to 9 mo, they consumed daily one of the study cereals. With each cereal, 2 infants had mild ID, a prevalence of 4.2%, but no infant developed ID anemia. There were no differences in iron status between study groups. Iron intake from the study cereals was (mean ± SD) 1.21 ± 0.31 mg?kg(-1)?d(-1) from Cereal L and 1.07 ± 0.40 mg?kg(-1)?d(-1) from Cereal M. Eleven infants had low birth iron endowment (plasma ferritin < 55 μg/L at 2 mo) and 54% of these infants had ID with or without anemia by 4 mo. We conclude that electrolytic iron and ferrous fumarate were equally efficacious as fortificants of this infant cereal.     

Exclusive breast-feeding for 6 months, with iron supplementation, maintains adequate micronutrient status among term, low-birthweight, breast-fed infants in Honduras

There is little information on the risk of micronutrient deficiencies during the period of exclusive breast-feeding. We evaluated this among term, low-birthweight (LBW; 1500-2500 g) infants in Honduras. Mother-infant pairs were recruited in the hospital and assisted with exclusive breast-feeding during the first 4 mo. At 4 mo, infants were randomly assigned to either continue exclusive breast-feeding to 6 mo (EBF; n = 59) or be given iron-fortified complementary foods (rice, chicken, fruits, and vegetables) from 4 to 6 mo while continuing to breast-feed (SF, n = 60). Blood samples were collected at 2, 4, and 6 mo and analyzed for hemoglobin (Hb), hematocrit, plasma ferritin, % transferrin saturation, vitamin A, vitamin B-12, folate, zinc, and erythrocyte folate. Infants with Hb < 100 g/L at 2 or 4 mo were given medicinal iron supplements for 2 mo; the proportion administered iron drops did not differ significantly between groups. There was no significant effect of complementary foods on indices of vitamin A, B-12, folate, or zinc status. Among infants not given medicinal iron at 4-6 mo, iron status was higher in the SF group than the EBF group. In those given medicinal iron at 4-6 mo, iron status was higher in the EBF group, suggesting that complementary foods interfered with iron utilization. About half of the infants were anemic by 2 mo, before the age when complementary foods would be recommended. This supports the recommendation that LBW infants should receive iron supplementation in early infancy. Given that infants given iron supplements did not benefit from complementary foods at 4-6 mo, we conclude that exclusive breast-feeding for 6 mo (with iron supplementation) can be recommended for term, LBW infants.     

Selenium status of exclusively breast-fed infants as influenced by maternal organic or inorganic selenium supplementation

A longitudinal dietary Se supplementation study on lactating mothers was performed to determine the possibilities of improving the Se status of exclusively breast-fed infants. A total of 200 mothers randomized into three groups received either no Se supplements, 100 micrograms of selenite, or 100 micrograms of yeast-Se daily. Maternal and infant serum Se concentrations showed a linear correlation during exclusive breast-feeding. Yeast-Se in the dose administered was safe and more effective than selenite in increasing the Se concentrations of maternal serum and milk, and infant serum. The mean estimated daily Se intakes of the infants were 7.7 +/- 2.2, 8.9 +/- 2.2, and 11.5 +/- 4 micrograms, in the control, selenite, and yeast-Se groups respectively. Though the infant Se intakes of the unsupplemented and selenite-supplemented mothers were below the lower limit of the safe and adequate range as set by the US National Research Council, their serum Se concentrations increased steadily over the 6-mo study period. As maternal serum Se also increased by over 50% during the same period the results suggest that a maternal daily intake of 50-75 micrograms is adequate during lactation.     

Fat-soluble vitamins in breast-fed preterm and term infants

OBJECTIVE: To examine the supply and status of fat-soluble vitamins in very low birth weight (VLBW) infants compared to a reference group of normal birth weight (NBW) infants. DESIGN: A longitudinal study of VLBW infants in the early neonatal period. Blood samples were drawn at 1 week of age and at discharge from hospital. Plasma was analyzed for the fat-soluble vitamins: retinol, 25-OH-vitamin D, alpha-tocopherol and phylloquinone (vitamin K(1)) using high-performance liquid chromatography. SUBJECTS: A total of 40 VLBW infants were included in the study. A reference group of 33 NBW infants was randomly selected from one of our previous studies. RESULTS: The VLBW infants received fortified human milk, and daily oral vitamin supplement (Multibionta). In VLBW infants, plasma retinol concentrations decreased and plasma 25-OH-vitamin D increased during the study period. VLBW infants had significantly lower plasma retinol (0.3 vs 0.7 mu M) and higher plasma 25-OH-vitamin D (166 vs 25 nM) at discharge compared to NBW infants. Plasma phylloquinone concentration in VLBW infants was very high (53 ng/ml) at one week of age, especially in the youngest infants (192 ng/ml), but decreased rapidly during the study period resulting in low/normal plasma concentrations (0.9 ng/ml) at discharge. CONCLUSIONS: We observed alterations in plasma concentration of retinol and 25-OH-vitamin D in VLBW infants in the early neonatal period, resulting in marked differences between VLBW at discharge and NBW. Further trials are needed to evaluate whether changes in vitamin supplementation may improve clinical outcome in VLBW infants.