Getting to know your gut bacteria

The ability to sequence DNA has made it possible for scientists to learn about our microbiome—all the organisms that live on and within us. At the moment, there’s a big push to learn about the bacteria in our guts, which harbor about 1000 different species of bacteria. Researchers have found that bacteria affect most of our physiologic functions, including our immune systems. One of the ways scientists are learning about gut bacteria is to study the variations in bacteria among diverse populations all over the world.

To determine the relationships between gut bacteria and health, they’re also comparing the bacteria of healthy individuals to those of diseased people and have found some connections. So far, it appears that gut bacteria play a role in the development of arthritis, colorectal cancer, colitis, obesity, diabetes, and even heart diseases. They have also found that most of these diseases are more prevalent in the US than in many other populations. A key reason for the link between our microbiome and these diseases has to do with our fiber-poor diets—a paltry 15 grams of fiber daily. As hunter-gatherers, we were likely eating close to ten times the amount of fiber than we do today. (In last week’s post, I explained how fiber keeps our gut bacteria in good working order.) Our use of antibiotics, which negatively affect gut bacteria, also contribute to the problem.

Unfortunately, there’s not a lot you can do to change the makeup of your gut bacteria other than increase dietary fiber and, maybe, probiotic food, such as yogurt. These foods can alter the relative abundance of the various species. But to dramatically change the population of bacteria you’d need a fecal transplant, which the FDA approves only if you are harboring Clostridium difficile (c. diff). Of course, you can always do it yourself.

In the interests of science, I signed up for one of the studies: the American Gut Project. (This requires a stool sample, of course.) I got a lengthy report complete with colorful graphs that show the relative abundance of the various phyla and families of bacteria in my gut. Unfortunately, the report doesn’t rate the quality of my bacteria—whether good or bad. Elsewhere, however, I learned that a ratio of more Bacteroidetes to fewer Firmicutes (these are phyla)—is correlated with lower body mass index. Unfortunately, my ratio is the opposite, but not by much. I’m a little fat. I think that means I need to eat more fiber. On a happier note, I did learn that my most abundant microbe (family Prevotella) is inversely correlated with Parkinson’s disease. So that’s something.

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