Friday, June 7, 2013

More on the "Teeming, Quasi-Wilderness" Within Us

Apparently I'm not the only one thinking about the microbiome these days. Many of you have probably already seen Michael Pollan's article in The New York Times Magazine a couple of weeks ago.

A couple of quotes jumped out at me:

"Our resident microbes also appear to play a critical role in training and modulating our immune system, helping it to accurately distinguish between friend and foe and not go nuts on, well, nuts and all sorts of other potential allergens. Some researchers believe that the alarming increase in autoimmune diseases in the West may owe to a disruption in the ancient relationship between our bodies and their 'old friends' — the microbial symbionts with whom we coevolved."

The new thinking on the microbiome and how its diversity of bacteria are essential to our health won't, I don't think, lead to a cure for T1D; but I do think that once scientists understand how to rebuild a healthy microbiome, the incidence of T1D and other autoimmune diseases will drop. I also think diabetics who are able to recreate a healthy microbiome may see their insulin needs decrease.


Anyone can learn exactly what bacteria live inside them by getting tested through the American Gut project. Comparisons of "American" guts with those who don't take antibiotics and eat no processed food have shown stark differences:

"Preliminary results indicate that a pristine microbiome — of people who have had little or no contact with Westerners — features much greater biodiversity, including a number of species never before sequenced, and, as mentioned, much higher levels of prevotella than is typically found in the Western gut. Dominguez-Bello says these vibrant, diverse and antibiotic-na├»ve microbiomes may play a role in Amerindians’ markedly lower rates of allergies, asthma, atopic disease and chronic conditions like Type 2 diabetes and cardiovascular disease."

The scientists who specialize in this field place little faith in the probiotics proliferating on grocery shelves. But here are the measures they do tend to take in terms of building the health and diversity of their gut bacteria:

"I began asking them ... how, in light of what they’ve learned about the microbiome, they have changed their own diets and lifestyles. Most of them have made changes. They were slower to take, or give their children, antibiotics. (I should emphasize that in no way is this an argument for the rejection of antibiotics when they are medically called for.) Some spoke of relaxing the sanitary regime in their homes, encouraging their children to play outside in the dirt and with animals — deliberately increasing their exposure to the great patina. Many researchers told me they had eliminated or cut back on processed foods, either because of its lack of fiber or out of concern about additives. In general they seemed to place less faith in probiotics (which few of them used) than in prebiotics — foods likely to encourage the growth of “good bacteria” already present. Several, including Justin Sonnenburg, said they had added fermented foods to their diet: yogurt, kimchi, sauerkraut. These foods can contain large numbers of probiotic bacteria, like L. plantarum and bifidobacteria, and while most probiotic bacteria don’t appear to take up permanent residence in the gut, there is evidence that they might leave their mark on the community, sometimes by changing the gene expression of the permanent residents — in effect turning on or off metabolic pathways within the cell — and sometimes by stimulating or calming the immune response."

Pollan later adds a bit more detail on the types of food to seek out in order to take care of the "teeming, quasi-wilderness" within:

"Viewed from this perspective, the foods in the markets appear in a new light, and I began to see how you might begin to shop and cook with the microbiome in mind, the better to feed the fermentation in our guts. The less a food is processed, the more of it that gets safely through the gastrointestinal tract and into the eager clutches of the microbiota. Al dente pasta, for example, feeds the bugs better than soft pasta does; steel-cut oats better than rolled; raw or lightly cooked vegetables offer the bugs more to chomp on than overcooked, etc. This is at once a very old and a very new way of thinking about food: it suggests that all calories are not created equal and that the structure of a food and how it is prepared may matter as much as its nutrient composition."

This field is still in its infancy, but I wouldn't be surprised if a decade or two down the road our thinking about autoimmune diseases like T1D—and perhaps about other scourges too, like cancer and heart disease—is inextricably linked to those trillions of bacteria that live inside us.

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