Domelloff et al. were the first to report the reference values for iron status variables in exclusively breastfed infants [13]. They reported Hb >10.5 g/dl as normal 2 SD cut-off at four and six months of age. The 2 SD cut-offs for serum ferritin were < 20 ng/ml and < 9 ng/ml at these ages respectively. In the present study, none of the babies in either group were found to be iron deficient at 14 weeks and 6 months although at 14 weeks of life eight babies were anemic as per these criteria [13]. Their serum ferritin was >41 ng/ml which signified that iron stores were normal. The Hb of all these babies increased to non-anemic ranges (>10.5 g/dl) with normal age-specific serum ferritin levels at six months. The low Hb level in these babies at 14 weeks was not due to iron deficiency but perhaps was a result of delayed onset of haematopoiesis compared to their peers [3]. Once the trigger to start Hb formation was activated these babies produced enough Hb later on, and were able to overcome their earlier deficiency.
Similarly at six months of age, none of the babies in either group were iron-deficient or anemic with a lone exception. In one baby of anemic mother, who had normal Hb level at 14 weeks, the Hb level fell just below 10.5 g/dl (10.4 g/dl) with age-normal serum ferritin level (11 ng/ml) which indicated that the baby was not iron deficient [13]. Our observations regarding Hb, SI, TIBC, %TS and serum ferritin of babies in both groups, at six months of age, were in concordance with other studies [14–16].
Pisacane et al. studied the iron status of 30 infants who had been breastfed until their first birthday and who had never received cow milk, medical iron or iron-enriched formula and cereals [17]. None of the infants who were exclusively breastfed for seven months or more and 43% of those who were breastfed for a shorter duration, were anemic (Hb < 11 g/dl) at 12 months of age. The duration of exclusive breastfeeding was significantly longer among non-anemic infants (6.5 vs 5.5 months) [17]. Murray et al. studied the effect of iron status of Nigerian mothers on the concentration of iron in breast milk and reported that, infants feeding entirely on breast milk appeared to have normal iron status at six months [14]. Duncan et al. followed 33 exclusively breastfed infants from birth to six months for their iron status [15]. They concluded that infants who were exclusively breastfed for the first six months of life were not at a higher risk for the development of iron deficiency anemia or the depletion of iron stores during that time [15].
In another study by Lonnerdal and Hernall of exclusively breastfed infants and infants fed cow's milk based formula containing either 4 mg iron/l or 7 mg iron/l, there were no significant differences in the haematological indices among the groups at 6 months age and the iron status of the infants was satisfactory [16]. They also found that the concentration of serum transferrin receptors was highest in breastfed infants, and lowest in the infants who received high concentration of iron (7 mg/l) [16]. This finding suggested that breastfed infants were probably on the verge of becoming iron deficient, although their serum ferritin levels and other haematological indices were normal. Interestingly, in the above study, the normal haematological values used for comparison were obtained from a selected group of healthy term infants (> 3 kg birth weight) who were receiving continuous iron supplementation during the first year of life [18, 19], but still breastfed infants were not seen doing badly.
As we have reported previously, breast milk iron and lactoferrin concentration had no relationship with the mother's Hb and iron status [11]. The wide range in the breast milk iron values reported in the literature may be due in part, to differences in sampling procedures as well as stage of lactation. Iron content of human milk is highest in early transitional milk (0.97 mg/ml) but decreases steadily during lactation, reaching a level of approximately 0.35 mg/ml at 1 month of lactation to 0.20 mg/ml at 6 months [11, 20–22]. In the present study from birth to six months, the mean breast milk iron ranged from 0.89 to 0.26 mg/l in the non-anemic (group A) and 0.86 to 0.33 mg/l in the anemic (group B) mothers. Mean breast milk lactoferrin levels in non-anemic mothers (group A) were 12.02 mg/ml, 5.84 mg/ml and 5.85 mg/ml respectively at day 1, 6 weeks and 6 months while in anemic mothers (group B), levels were 12.91 mg/ml, 6.68 mg/ml and 6.37 mg/ml respectively at the same time points. No significant difference was noted in the breast milk iron and lactoferrin between non-anemic and anemic mothers on day 1, 14 weeks and 6 months after delivery.
Houghton et al. studied breast milk lactoferrin levels in relation to maternal nutritional status [23]. Lactoferrin concentration was significantly higher in the first 15 days of lactation (ranging from 2.82 mg/ml to 3.49 mg/ml) than later (ranging from 0.66 mg/ml to 1.42 mg/ml). There are few other studies regarding breast milk lactoferrin concentration mainly during early lactation [8, 24, 25]. Lien et al. estimated lactoferrin in the breast milk of mothers from nine countries by HPLC method and reported that its level ranged from 1.37 to 2.12 g/L (mean 1.83 ± 0.67 g/L) and was significantly lower in Mexican and Australian mothers compared to Canadian, Chinese and British mothers [26]. Thus ethnic and racial factors do appear to affect lactoferrin levels in the breast milk. In the above study, Indian mothers were not included. The lactoferrin levels in our study were higher when compared to the available literature. However, lactoferrin levels in our mothers, both non-anemic and anemic, behaved in a completely different way from that reported by Lien et al. [26]. The lactoferrin levels in our mothers decreased significantly from day 1 to 14 weeks of lactation but remained fairly consistent from 14 weeks to 6 months, unlike Australian mothers, where lactoferrin levels remained fairly constant until 350 days of lactation duration, and in contrast to British mothers in whom lactoferrin declined sharply in the same period. Is the obvious difference in the breast milk lactoferrin values in our study because of the method of estimation of lactoferrin, subject variation (race/ethnicity) or a small sample size (n = 13 in each group)? It is a matter for further research. The study has conclusively showed that there was no correlation between the iron status of exclusively breastfed infants with breast milk iron and lactoferrin until six months of age.
Our findings of breast milk iron levels were in concordance with other studies [8, 20, 21]. Many studies in the past have assessed the iron status of exclusively breastfed infants, but unfortunately, very few have attempted to look at the relationship between breast milk iron and lactoferrin with the iron status of exclusively breastfed infants in first six months of life. It was not surprising that exclusively breastfed infants neither developed iron deficiency nor iron deficiency anemia. The breast milk iron and lactoferrin are efficiently absorbed in the gut and together with body iron stores, the iron supply is sufficient to maintain normal iron metabolism in the first six months of life in term AGA babies. Therefore, there is no need to add iron-rich foods or therapeutic iron to exclusively breastfed term infants until six months of life lest it may harm the baby [27].
Comments
View archived comments (1)