Your Internal Ecology

People as Ecosystems

On this blog, we stress that individuals are not isolated units, and nowhere is this more apparent than in the microbial ecosystem that is the human body. We are in fact hosts to microbial organisms that outnumber our own cells by more than 10 to 1! These organisms can be both helpful, like the species of Staphylococcus bacteria that competitively inhibit pathogenic Staph strains; and they can be harmful, like the C. difficile that causes colon inflammation. The Human Microbiome Project, a $115 million research effort with the NIH, attempts to catalogue the variety of species and genetic material in that very local ecology.  The results have already turned up a startling diversity among the microbiomes of the 250 participants--as well as the conclusion that no two individuals host the same organisms.

You Are What--And Whom--You Eat!

The gut is a particularly important site for microbial life, and the profile of flora there is referred to as the enterotype. A seminal article in a 2011 issue of Nature identified three major enterotypes that occur in humans, though there is recent debate as to whether those types are discrete categories or represent points on a spectrum, along which any individual's gut microbiota may slide over time. Whether static or not, though, it is clear that the composition of gut bacteria plays an important role in metabolism, immunity, and even mental health. The vagus nerve, which connects the brain to the gut (and in fact is the only cranial nerve to innervate the body), may be a connection that future psychiatrists exploit to improve mental health via the gut.

Perhaps unsurprisingly, the enterotype has been shown to vary with diet.  Regular consumption of meat, carbohydrates, and alcohol can alter proportions of various microbial strains.  The diet connection also is apparent in disease states. A 2012 study examining the effects of concentrated milk fats in the Western diet showed that these fats, found mostly in processed foods, "disrupt the delicate truce between the immune system and the complex but largely beneficial mix of bacteria in the intestines."  The imbalance can eventually trigger immune disorders like inflammatory bowel disease.  Conditions like diabetes and obesity are being linked to specific microbial conditions as well, suggesting some hope that health providers could intervene in those disease states via manipulations of gut microbes.

The ingestion of antibiotics is another factor that significantly affects microbial composition. The indiscriminate knockout of gut flora with a broad-spectrum antibiotic triggers an ecological succession event, somewhat like logging in a complex forest ecosystem.  The destruction creates opportunities for pathogenic bacteria to take hold in a less competitive environment.  While treatments with antibiotics in cases of serious infection are often life saving and absolutely necessary, the routine ingestion of antibiotics may undermine the health of an individual's gut ecosystem.

Living Foods

Probiotic foods contain microorganisms that promote a healthy gut ecology.  The recent popularity of these foods reflects a growing public awareness about the importance of eating smart to host good inner bacteria.  Probiotic options include more familiar items, like yogurt and pickles, as well as their exotic cultured and fermented friends--like kefir, kimchi, sauerkraut.  Probiotic capsules are also increasing in availability, and offer a serious doses of friendly bacteria to your gut.

So next meal, think about all the other organisms waiting eagerly to see what's on their plate.  Consider sending them some real food to thrive on--or some probiotic comrades--and see how tending your inner microbial garden improves your health!