Study: Cow's milk doubles babies' risk for asthma compared with breastfeeding

Infants who have breast milk supplemented with cow's milk-based formula are at higher risk for asthma, a study indicated. Photo by lgrodela/Pixabay

Oct. 2 (UPI) -- Infants who receive cow's milk-based formula in addition to breast milk are nearly twice as likely to develop asthma or recurrent wheeze, according to a study published Friday by JAMA Network Open.

Among infants who received milk formula as a supplement to breastfeeding from birth to 5 months, 18% developed asthma or recurrent wheezing, the data showed.

Conversely, only 10% of the infants who were breastfed only -- as well as those who received breast milk plus amino acid-based elemental formula -- during their first few months of life experienced these breathing issues, the researchers said.

"Breastfeeding with or without elemental formula for the first three days or more of life appeared to decrease the risk of asthma or recurrent wheeze in young children compared with breastfeeding plus a small amount of cow's milk formula from the first day of life," wrote the researchers from Jikei University School of Medicine in Tokyo.

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The U.S. Centers for Disease Control and Prevention and World Health Organization both recommend breastfeeding babies for at least six months after birth.

However, not all women are able to breastfeed for a variety of reasons and, in these cases, iron-fortified formulas are recommended.

For this study, researchers followed the health of 302 infants through their respective second birthdays.

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Of the 151 who received no cow's milk-based formula, 15 -- or 10% -- developed asthma or recurrent wheeze, compared with 27 -- or 18% -- of those who did take cow's milk, the data showed.

Among babies with above-average vitamin D levels at age 5 months, asthma or recurrent wheeze developed in 25% of those who received cow's milk compared with 6% of those who didn't, the researchers said.

Although the researchers did not explore why these differences occurred, they suggest that human breast milk may contain certain chemicals and nutrients that bolster the immune system and gut bacteria of babies.

"However, these mechanisms remain essentially unknown and further research is necessary," they wrote.