The health benefits of breast-feeding have been intensely researched, but it's less clear exactly how long exclusive breast-feeding, without the addition of other foods, should be kept up. While six months of exclusive breast-feeding is often recommended, a new study shows that babies who began eating infant cereal at 4 months old had higher levels of iron than those who were exclusively breast-fed for six months.
Both groups of babies had sufficient iron levels, and there were no differences in rates of anemia, the researchers said.
"The biological significance of the higher [iron] levels among those infants who began complementary feeding at 4 months of age remains to be determined," the researchers wrote in their study, published Nov. 12 in the journal Pediatrics.
In 2001, the World Health Organization (WHO) changed its recommendation on breast-feeding to say that infants should be exclusively breast-fed for the first six, rather than the first four, months of life. The leading pediatricians' group the American Academy of Pediatrics also recommends that babies be exclusively breast-fed for six months.
The reason the WHO changed its recommendation was to provide better nutrition for babies in low-income countries, where water and other foods may be contaminated or nutritionally inadequate, according to the study.
"In high-income countries, the evidence for recommending six months of exclusive breastfeeding is less clear," the researchers wrote in their study, adding the WHO has requested that researchers conduct randomized controlled trials — the gold standard in medical studies — to look at the issue. The new study is among the first to do just that.
In the study, mothers of 100 infants in Iceland who were exclusively breast-feeding their babies were randomized to begin giving other foods at either 4 months or 6 months old. The researchers, led by Olof H. Jonsdottir of the University of Iceland, measured the babies' growth rates and iron levels when they were 6 months old.
Results showed that higher iron levels were seen in the infants who began eating other foods at 4 months old. There was no difference between the groups in terms of the babies' weight gain or growth.
For the babies given other foods, the main source of iron was infant cereal, though infant formula and fruit purees also contributed.