“The big problem with the Western diet,” Stephen O’Keefe said, “is that it doesn’t feed the gut, only the upper G I. All the food has been processed to be readily absorbed, leaving nothing for the lower G I. But it turns out that one of the keys to health is fermentation in the large intestine.” And the key to feeding the fermentation in the large intestine is giving it lots of plants with their various types of fiber, including resistant starch (found in bananas, oats, beans); soluble fiber (in onions and other root vegetables, nuts); and insoluble fiber (in whole grains, especially bran, and avocados).
With our diet of swiftly absorbed sugars and fats, we’re eating for one and depriving the trillion of the food they like best: complex carbohydrates and fermentable plant fibers. The byproduct of fermentation is the short-chain fatty acids that nourish the gut barrier and help prevent inflammation. And there are studies suggesting that simply adding plants to a fast-food diet will mitigate its inflammatory effect.
The outlines of a diet for the new superorganism were coming clear, and it didn’t require the ministrations of the food scientists at Nestlé or General Mills to design it. Big Food and Big Pharma probably do have a role to play, as will Jeffrey Gordon’s next-generation synbiotics, in repairing the microbiota of people who can’t or don’t care to simply change their diets. This is going to be big business. Yet the components of a microbiota-friendly diet are already on the supermarket shelves and in farmers’ markets.
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.