"Breast milk is the optimal food for infants during the first months of life," lead researcher Dr Inger Kull of the Karolinska Institute in Stockholm, Sweden is reported to have said. "But whether or not breastfeeding reduces the risk of asthma has been debated."

Through her milk, a mother transfers 'good' bacteria, antibodies and proteins that can help thwart infection. But the evidence for how breastfeeding might influence the later development of asthma remains confusing, with various studies suggesting protective, neutral and even detrimental effects.

The study

Kull and her colleagues decided to look into the relationship a little differently than previous studies. They followed nearly 4,000 Swedish children over eight years, noting which received short- or long-term, as well as exclusive or partial, breastfeeding.

The findings

The team found that about 12% of children who were exclusively breastfed for at least the first 4 months of life developed asthma by age 8, compared with 18% of those breastfed for a shorter amount of time.

This translated into a 37% lower risk of asthma for those breastfed for 4 months or longer, after adjusting for other risk factors such as maternal smoking and birth weight. The difference appeared to be driven mostly by allergy-related cases of asthma. The extended and exclusive diet of breast milk also resulted in better lung function at age 8.

Of course, not all mothers have the desire or ability to solely breastfeed for their child's first months. For these women, Kull suggests that even partial breastfeeding can somewhat reduce the risk of asthma.

Pic: Nick Winchester