The them in us

My native inclination this time each year is to turn my attention from matters purely medical, and dwell somewhat preferentially on the humanistic: peace on earth, good will toward men (and women), and all that. I turn this year to the solidarity among the crowd within each of us for some help.

I mean our microbiome, and the particular goad to make that the focus of this homily is a recent commentary in JAMA, reflecting on the potential importance of those bacteria, and their genes, to the risk for, and management of, rampant obesity and diabetes.

The microbiome, as you likely know, refers to the vast village within, necessary indeed not only to raise a human child, but to sustain a human adult. Trillions of bacteria inhabit every one of us, and it is doubtful we could live at all were it not so. The exact numbers are a topic of some controversy, as is the margin by which our bacteria outnumber our cells; but that they do outnumber our cells is established. The human component of every human is something of a rounding error relative to the bacterial.

That is all the more so when genes are considered. As the JAMA article indicates, bacterial genes may outnumber our own by two to three orders of magnitude. That’s a big deal, because those genes manufacture compounds that become part of our inner worlds, just as the products of our own genes do. We are massively influenced, in every aspect of our physiology and metabolism, by the citizens of a diverse internal community.

How diverse? That’s the most interesting part of all this. Biological diversity is best measured at the level of DNA, certainly not appearance.

Where it counts, almost all biological diversity is expressed by bacteria. Stated differently, the deep, meaningful biological diversity among bacterial species is far greater than the diversity among all other living things, including both plants and animals. Down near the bedrock of biology, penguins and pine trees are not only more alike, but almost indistinguishably similar, compared to the diversity just among bacteria.

That invites us to ponder the comparative similarities between any two of us: Palestinian and Israeli, perhaps, Hindu and Muslim, male and female, black and white.

In the case of the microbiome, that astonishingly diverse community, itself only a sliver of the diversity among all bacteria, functions in stunning solidarity with both itself and us, the host. Our bodies provide the real estate those bacteria call home, and deliver to them their essential sustenance. They, in turn, mix their gene products with our own, altering everything from the integrity of our cells and tissues, to the balance of our many hormones.

It is indeed now clear this influence pertains powerfully to the risk of such conditions as obesity and diabetes. But important as the microbio-mial influence surely is, I think we tend to get a bit carried away. Yes, a salutary balance of bacterial flora tends to favor a lean and healthy host; but so, too, do eating genuinely well and exercising routinely. Eating well and being active may not make every body lean, but when they are truly done, they truly work far more often than not.

There was very little obesity or type 2 diabetes 100 years ago, and virtually none in children. Was that because our predecessors had deep and ancient knowledge we’ve lost of the care and feeding of the microbiome? Of course not; they knew nothing of it. Knowledge of the microbiome and its importance is very modern. Tempting as it is to think we need to know what to feed our microbiota to make ourselves well, history and epidemiology indicate the opposite is true.

When humans take good care of themselves, they tend to thrive. Presumably, so too do our symbionts, if only by happenstance. Diet and exercise and healthy living work reliably to promote health and prevent disease, whether or not influence on the microbiome is part of the pathway.

To combat obesity and diabetes, and the other great scourges of modern epidemiology, will require that our perspective evolve past a choice between pursuing the details we don’t have, and applying the reliable knowledge we do.

The next, great opportunity to add years to lives, and life to years, resides in the domain where those two are reconciled.

But advances in health offer little to cheer if we cannot find our way to reconciliations among ourselves.

To combat the arguably greater scourges of division, distrust, and hate, we must evolve a perspective that takes us past us and them, to common cause. Perhaps the “them” within each of us can help, for they remind us that in the vast sweep of biological diversity, all of humanity is a very close-knit family.

Families, of course, can differ- but love generally prevails. May it be so. Happy holidays, cousin.