Breast milk helps lungs but not if mom has asthma

CHICAGO (Reuters) - Breast-feeding seems to protect children from asthma later in life, but only when the mother does not have the respiratory disorder herself, U.S. researchers said on Thursday.

They found that breast-feeding for more than four months helped improve lung function in children whose mothers did not have asthma.

But breast-fed children whose mothers had asthma did not benefit and actually showed a significant drop in lung function later in life.

That does not mean women with asthma should stop breast-feeding.

The researchers cautioned that the study, published in the American Journal of Respiratory and Critical Care Medicine, was preliminary and the findings needed more study.

Breast milk is almost always considered best for infants. It can be digested easily and supplies antibodies that can protect babies from bacterial and viral infections, including many of the respiratory tract.

Dr. Theresa Guilbert of the University of Wisconsin-Madison wanted to see if longer breast-feeding -- lasting four months or more -- improved lung function in children.

She and colleagues at the Arizona Respiratory Center analyzed data from the Children's Respiratory Study in Tucson, which followed 1,246 healthy infants through adolescence.

Of those, 697 had lung function tests from the ages of 11 to 16 that evaluated air flow and lung volume.

For the most part, breast-fed children with non-asthmatic mothers had better lung volume and no decrease in air flow.

But children of mothers with asthma who were breast-fed four months or more did not show any improvement. In fact, these children had a significant reduction in airflow.

The reason, Guilbert suggested, may be altered lung growth.

Guilbert believes breast milk may contain certain factors that promote lung development, factors that may be impaired in mothers with asthma.

"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 breast-feeding," she wrote.

Researchers found a similar effect in mice born to non-asthmatic mothers who were breast-fed by mothers with asthma. These mice developed airway inflammation.

"It is important to emphasize that the clinical significance of these findings is unknown," Guilbert wrote.

"Further study is needed to confirm our findings and to determine a biological basis for the relationships observed."