ANDREW SWIFT
While gut microbiota appear to have both positive and negative impacts on our health, in the guts of healthy, lean individuals, the good outweighs the bad. Gut bacteria, most of which reside in the large intestine, process many otherwise indigestible components of foods, converting them into an estimated 10 percent of our daily energy supply. But in addition to eking out additional nutrients from our food, gut bacteria also produce a number of metabolic by-products that improve our immune systems, strengthen the lining of the gut—our best barrier to infection—and confer anticancer benefits.