The findings, published online in the International Breastfeeding Journal, support experts' belief that breast milk alone provides most infants with adequate nutrition for the first six months of life.
Breast milk is low in iron, but infants can absorb it much more easily than they absorb the iron in fortified formula. Healthy full-term infants are also born with enough iron stores to make deficiency unlikely in the first six months.
In general, it's recommended that breastfed babies start on iron-fortified foods, like infant cereal, at about six months.
In the current study, Indian researchers followed 129 full-term babies born to 68 mothers with normal iron stores or to 61 mothers with iron- deficiency anaemia. The mothers took iron and folic acid supplements as their obstetricians advised, but their infants were exclusively breastfed, without supplemental iron.
At six months of age, none of the babies were iron-deficient, regardless of whether their mother had been anaemic, according to the researchers, led by Dr. Shashi Raj of the University College of Medical Sciences in Delhi.
It's "not surprising" that these infants had sufficient iron levels, the researchers add, given how well breast-milk iron is absorbed and the amount of iron full-term babies have at birth.
They conclude that there is no need to add iron-rich foods or iron drops to the diets of exclusively breastfed full-term infants before the age of six months.
The findings do not apply, however, to babies born prematurely, as their iron stores at birth are typically depleted; doctors usually recommend that breastfed preemies start on supplemental iron early on.