Gut Microbiome of Infants

According to a new study published this past Monday in Nature Medicine, researchers link the gut microbiome of one month old infants to an increased risk of allergies and asthma later in life. This paper identifies that imbalances in the gut microbiome in at-risk infants causes immune dysfunction, leading to a hyperactive immune system.

Many studies have linked the early exposure to beneficial microbes in the environment to numerous health benefits. I previously shared a study published last year the journal Clinical & Experimental Allergy that revealed infants with a lower diversity of gut bacteria at three months of age are at a higher risk of becoming sensitized to foods such as milk, egg or peanut by the time they reach one year of age. In addition, infants who developed food allergies also had a dysbiosis specifically associated with the bacteria Enterobacteriaceae and Bacteroidaceae.

Past research from the University of British Columbia demonstrated that three month old infants had low levels of four key types of gut bacteria, and were significantly more likely to show symptoms of asthma at their first birthdays than infants with normal levels of these bacteria.

In this new study, researchers collected stool samples from the infants. Based the team’s two and four year follow-up data, the size of this at-risk group was consistent with the rate of allergic asthma in the general population. The microbial diversity analysis demonstrated that these infants were missing specific beneficial bacteria, and also had high levels of specific opportunistic bacteria.

The researchers also identified that a healthy microbiome contains a wide range of molecules that can decrease inflammation and keep the immune system in check. In contrast, these key anti-inflammatory molecules were not present in the at-risk infants.

We have co-evolved with microbes over the past several decades but our lifestyles have changed dramatically reducing our exposure to these microbes.

There are several variables that may contribute to the infant’s gut microbiome at this early age. Breastfeeding, vaginal births and pets in the home during the first year of life all are associated with protective effects against asthma and allergies. Cesarean delivery may affect the early diversity of intestinal bacteria. The gastrointestinal tract of infants becomes colonized immediately after birth with environmental microorganisms, mainly from the mother. The intestinal microbiota of infants delivered by cesarean delivery appears to have less diversity and is characterized by an absence of Bifidobacteria species than the microbiota of vaginally delivered infants. Mothers using formula instead of breast milk is yet another factor. Breast milk is an early stimulator of the intestinal flora, and lacking this dietary support may be a contribution to food sensitization. In these circumstances, a probiotic may be considered.