If Michael Pollan and the NYTImes are to be trusted, the new hot-topic Frontier of Popular Medicine is the human (mostly intestinal) microbiota:
… In sheer numbers, these microbes and their genes dwarf us. It turns out that we are only 10 percent human: for every human cell that is intrinsic to our body, there are about 10 resident microbes — including commensals (generally harmless freeloaders) and mutualists (favor traders) and, in only a tiny number of cases, pathogens. To the extent that we are bearers of genetic information, more than 99 percent of it is microbial. And it appears increasingly likely that this “second genome,” as it is sometimes called, exerts an influence on our health as great and possibly even greater than the genes we inherit from our parents. But while your inherited genes are more or less fixed, it may be possible to reshape, even cultivate, your second genome.
Justin Sonnenburg, a microbiologist at Stanford, suggests that we would do well to begin regarding the human body as “an elaborate vessel optimized for the growth and spread of our microbial inhabitants.” This humbling new way of thinking about the self has large implications for human and microbial health, which turn out to be inextricably linked. Disorders in our internal ecosystem — a loss of diversity, say, or a proliferation of the “wrong” kind of microbes — may predispose us to obesity and a whole range of chronic diseases, as well as some infections… (Researchers use the word “microbiota” to refer to all the microbes in a community and “microbiome” to refer to their collective genes.) We’ve known for a few years that obese mice transplanted with the intestinal community of lean mice lose weight and vice versa. (We don’t know why.) A similar experiment was performed recently on humans by researchers in the Netherlands: when the contents of a lean donor’s microbiota were transferred to the guts of male patients with metabolic syndrome, the researchers found striking improvements in the recipients’ sensitivity to insulin, an important marker for metabolic health. Somehow, the gut microbes were influencing the patients’ metabolisms…
These claims sound extravagant, and in fact many microbiome researchers are careful not to make the mistake that scientists working on the human genome did a decade or so ago, when they promised they were on the trail of cures to many diseases. We’re still waiting. Yet whether any cures emerge from the exploration of the second genome, the implications of what has already been learned — for our sense of self, for our definition of health and for our attitude toward bacteria in general — are difficult to overstate. Human health should now “be thought of as a collective property of the human-associated microbiota,” as one group of researchers recently concluded in a landmark review article on microbial ecology — that is, as a function of the community, not the individual….
Full-service sidebar to the main article includes the following exchange:
Aside from eating fermented foods, and not going nuts with the Purell, is there anything else that you recommend to improve your microbiome?
Garden. The exposure to soil is probably a good thing and, unless you live in a Superfund site, gardening is a good way to safely increase your “microbial pressure” on a daily basis. Having a dog may be a good thing too.
(Of course — and I say this as someone who gardens, with imported soil, on a dual Superfund site — for the urbanized mostly-coastal readers who are the NYTimes‘ target advertising audience, it’s safe to assume that one’s garden is contaminated, at the very least, by lead and other formerly-airborne twentieth-century pollutants. As a civil-engineer friend told us, “At least you have an EPA-certified list of all the poisons in your dirt.”)