New research revealed the effect breastfeeding and other factors have on a baby's immune system and susceptibility to allergies.

The findings back up the "hygiene hypothesis theory," which suggests early childhood exposure to microorganisms can have a significant impact on health, the Henry Ford health system reported. The gut microbiome contains billions of microbes and is believed to contribute to a wide variety of diseases, including "obesity, autoimmune diseases, circulating disorders and pediatric allergies and infection."

"For years now, we've always thought that a sterile environment was not good for babies. Our research shows why. Exposure to these microorganisms, or bacteria, in the first few months after birth actually help stimulate the immune system," said Christine Cole Johnson, chair of Henry Ford's Department of Public Health Sciences and principal research investigator. "The immune system is designed to be exposed to bacteria on a grand scale. If you minimize those exposures, the immune system won't develop optimally."

To make these findings, a team of researchers looked at six separate studies that assessed the influence of breastfeeding on babies' gut microbiomes, and how it contributed to health later in life. Using data from Henry Ford's long-running Wayne County Health, Environment, Allergy and Asthma Longitudinal Study (WHEALS), the researchers analyzed stool samples from infants taken at one month and six months after birth to see how the microbiome affected T-cells that regulate the immune system.

The researchers found breastfed babies had noticeable differences in microbiomes when compared with babies who were not breastfed. Breastfed babies at one month had a reduced risk of developing pet allergies. For the first time in medical history, the composition of the gut microbiome was linked to an increase in the T (Treg) cells.

"The research is telling us that exposure to a higher and more diverse burden of environmental bacteria and specific patterns of gut bacteria appear to boost the immune system's protection against allergies and asthma," Johnson concluded.

The findings are being presented at the annual meeting of the American Academy of Allergy, Asthma & Immunology in Houston.