Children breastfed as babies may have stronger lungs and a lowered risk of asthma compared to those who were fed infant formulas, according to new research.

Past studies have found conflicting results with the effects of breastfeeding on children’s lungs, and some studies have suggested that moms with asthma who breastfeed may be putting their kids in danger.

However Swiss and UK researchers found that breastfeeding is associated with improved lung function at school age, especially in children with asthmatic mothers in a study published on Friday in the American Journal of Respiratory and Critical Care Medicine.  

One of the studies consisted of about 1,500 UK children who were followed from birth in the mid-1990s, and from age eight to 14 the children were asked to come into the lab for a range of lung function and allergy tests.

The study also asked families to respond to surveys that related to breastfeeding, secondhand smoke exposures and other known factors associated with asthma risks in kids.

Researchers found that the longer kids were breastfed, the better they performed on one test that measured the speed of air coming out of their lungs, and kids who were breastfeed by an asthmatic mother for four months or longer had better score on the other tests that measured how much air the lungs can hold.

Researchers said there was not a link between better lung function and fewer childhood respiratory infections, which is a known benefit of breastfeeding.

Dr. Claudia Kuehni from the University of Bern, Switzerland and her team said that the boost in lung function that is attributed to breastfeeding seemed to make no difference in healthy kids, but on a wider scale, the findings suggest that breastfeeding would protect more kids from breathing problems.

A second group of researchers also followed infants from birth, but instead of testing lung function like in the first study, researchers asked parents of six-year-olds if their kids had ever been diagnosed with asthma, used an inhaler or wheezed in the last year.

Researchers from New Zealand collected data from more than 1,000 kids that included 200 with asthma at their last visit and found that there was a nine percent drop in asthma risk with each month of exclusive breastfeeding without any formula mixed in.

Karen Silvers and her team from the University of Otago in Christchurch published their findings on Sunday in the Journal of Pediatrics.

"I think the evidence is that breastfeeding increases lung volume, independent of if the mother is asthmatic or not," Dr. Wilfried Karmaus, who studies asthma at the University of South Carolina in Columbia, told Reuters.

"If the lung volume is increased, then you are less susceptible to get asthma," Karmaus said. "It's important even to tell asthmatic mothers to breastfeed their children."

Karmaus said that experts have suspected breast milk to carry immune cells related to allergies and asthma from the mother to the baby which lead to many believing that asthmatic moms who breastfeed may put their infants at risk of breathing problems, which resulted in concerned asthmatic mothers who avoided breastfeeding.

Karmaus indicated that the new findings suggest that mothers with breathing problems shouldn’t worry, and hypothesized that infants who suckle during breastfeeding may have stronger lungs that help protect against asthma later.

The World Health Organization recommends mothers to breastfeeding exclusively their infants for the first six months of life and maintained for two years or longer.