Gut Microbes Through the Years – From Birth to Adulthood

The human gut contains over 500 species of microorganisms and 70% of the immune system's cells. In perfect balance, gut bacteria is responsible for warding off disease and is involved in the synthesis of vital nutrients. But where do these microorganisms come from and how do they get inside of us in the first place?

 At Birth

The most important exposure to bacteria occurs as a newborn baby travels down the birth canal and into the world. The birth canal is lined with lactobacillus and other healthy bacteria. Unfortunately, this only happens in natural vaginal birth, and research has shown that babies delivered via Caesarean section do not receive the same vital, protective microbes as babies born vaginally. What to do in the case of a c-section, which oftentimes are medically necessary? Don’t worry! Recent studies indicate that these microbes can be restored at birth by slathering babies with a gauze pad that soaked up the microbes in their mothers' birth canal right before birth. Another way that babies can receive good bacteria is through skin-to-skin contact after they’re born.

The First Year

Breast milk is filled with hundreds of beneficial bacteria (probiotics) that colonize baby’s gut and prebiotics that feed the probiotics in baby’s gut. This will become the foundation of our immune function. If breastfeeding is not an option? Believe it or not, formulas based on goat milk instead of cow or soy have been shown to produce bacteria in babies that most closely resembles the bacteria produced from breast milk.


Get Dirty - Dirt is full of microbes and the human gut is actually primed for constant, low level exposure to these soil-based organisms. Playing outdoors and sampling the culinary offerings of garden soil all help seed the gut.


Lifestyle factors that play a role in gut health and the colonization of bacteria, good or bad, include diet, stress, sleep, antibiotic use, and exposure to environmental toxins.

 Although we have little control over the first microbes we are exposed to as infants, there are many steps you can take as an adult to tip the balance in your favor. For more on nourishing your gut microbes, check out our article When Good Guts go Bad Part 2: Repairing your Gut with the 5 Rs.