Breast-feeding has been known to have some advantages over the bottle—fewer ear infections, less diarrhea and fewer incidents of wheezing early in life.

Now, researchers have found that babies who are breast-fed for more than four months will have better lung function and breathe easier into their adolescent years as long as their mothers don’t have asthma or allergies.

Researchers at the Arizona Respiratory Center studied data from infants who were enrolled since birth and monitored through their adolescence in the Children’s Respiratory Study.

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Of the 679 participants who completed the data on infant-feeding and were tested for lung function between the ages of 11- and 16-years-old, overall, breast-fed children had good lung function into their teens.

However, more breathing problems associated with breast-feeding were only found in children of mothers with asthma or allergies.

“These findings suggest that growth factors in milk have the potential to modify lung development, which might account for some of the protective effect of breastfeeding against wheeze,” said Theresa W. Guilbert, M.D., of the Arizona Respiratory Center at the University of Arizona in Tucson, Ariz.

Guilbert said that a mother’s breast milk may contain certain factors that promote lung development. What, specifically, is still unknown.

“Longer breastfeeding in infancy is associated with improved lung function in later childhood with minimal effects on airflow in children of non-asthmatic mothers,” wrote Theresa W. Guilbert, M.D., of the University of Wisconsin-Madison and the Arizona Respiratory Center at the University of Arizona in Tucson. “However, longer breastfeeding in children of mother with asthma demonstrates no improved lung growth and significant decrease in airflows later in life.”

She added, “Breast-fed children with non-atopic and non-asthmatic mothers had an increase in lung volume and no decrease in their airflows. However, children of mothers with asthma who were breastfed four months or more did not demonstrate any improvement in lung volume. Further, they had a significant reduction in airflows, suggesting that the risk for increased asthma in children of asthmatic mothers may be partly due to altered lung growth.”

The study is in the American Journal of Respiratory and Critical Care Medicine, which is published by the American Thoracic Society.