Does breastfeeding protect children against asthma?

While breastfeeding has been thought to decrease children’s risk of developing allergies and asthma, a major new study counters that belief.

In the largest study of its kind, researchers with Uppsala University in Uppsala, Sweden, found that breastfeeding might increase the risk of developing hay fever and eczema. Plus, they said, breastfeeding does not have any clear effect on the risk of developing asthma, according to the article published in the Journal of Allergy and Clinical Immunology.

Individuals’ risk of having asthma and allergies depends on their genes, environment and lifestyle factors, wrote Weronica Ek, lead author and researcher at Uppsala University’s Department of Immunology, Genetics and Pathology.

However, studies on breastfeeding have shown inconsistent results. “Many studies have found breastfeeding to have a protective effect against asthma and allergy, while other studies have reported increased risk,” according to an Uppsala University statement.

Meanwhile, the large Uppsala University study examined self-reported data from more than 330,000 middle-aged individuals in the United Kingdom.

They found that increased socioeconomic status lowers the risk of asthma, while it increases the risk of developing hay fever. “These results are in line with the ‘hygiene hypothesis’, which states that growing up in a cleaner environment increases the risk of being diagnosed with allergies due to a lack of early childhood exposure to microorganisms, among other things,” Uppsala University said.

The study also showed that a high body mass index (BMI) increases the risk for asthma, hay fever and eczema. However, the risk for developing all of the conditions decreases in individuals with higher birth weight.

The researchers noted certain limitations to the study, including the fact that it is an observational study, which does not allow for clinical recommendations to be made. “In such studies, there may always be underlying factors that the researchers do not have information about, which are the true causes of the observed effects.”

For example, mothers who have hay fever, asthma or eczema themselves may have been advised to breastfeed or not to breastfeed, which may affect the study’s findings.

“It is well established that breastfeeding has a positive effect on the health of the baby. Even though we do not see a protective effect of breastfeeding on the risk of developing asthma or allergies, these results should not be used to recommend or discourage breastfeeding, since the present study only investigates the effect of breastfeeding on allergies and asthma,” Uppsala University said.

“However, we hope that our study can give a more correct picture of the health benefits of breastfeeding,” Ek added.