You and I are only 10 percent human: for every human cell in your body you have about 10 resident microbes — harmless freeloaders, mutually beneficial organisms, and a few pathogens. More than 99 percent of the genetic information we hold is microbial.
The gigantic number of microbes we harbour make it hardly surprising that their health is essential to our own. Problems with our internal ecosystem — such as an oversupply of one microbe, or a loss of species diversity — are now recognised as associated with or causes of obesity, other chronic health conditions, and various infections. This is why faecal transplants from a healthy person into a sick person’s gut can treat antibiotic-resistant intestinal pathogens; they re-establish a fully functional microbial community. Similarly, babies born by caesarean section have higher rates of allergy, asthma and autoimmune problems than babies who are colonised by their mothers’ secretions during vaginal delivery.
Most Western diets lead to the development of a microbiome less diverse and less resilient than those of people enjoying more traditional diets; moreover, our intake of antibiotics has a profoundly negative effect. We prune our internal microflora at our own peril.
Read more from Michael Pollan’s article ‘Some of My Best Friends Are Germs’ (The New York Times) here.