A breakthrough study from Harvard’s Peter J. Turnbaugh and Duke’s Lawrence David reveals some of the ways in which our diet shapes our microbiome — and thereby affects our ability to digest various types of food. In 2011, the researchers fed volunteers two very different diets. One group was given a high-protein diet consisting of bacon and eggs, spareribs, brisket, salami, cheese, and pork rinds. The other was fed a very high-fiber diet of fruits, vegetables, grains, and beans. Bacterial analysis of fecal samples collected before, during, and after the experiment showed that what each group ate had a huge — and almost immediate — effect on their gut bacteria.
Lo and behold, each group began to develop the very type of bacteria that would most help them digest the particular types of food they had just eaten. In just 24 hours, meat eaters saw an increase in bacteria that are resistant to bile acids (bile acids are a byproduct of the breakdown of meat). If you’re a meat-eater, you need those bacteria — so the microbiome responded. The vegetarian group had far fewer bile-resistant bacteria, because, given their diet, they didn’t need them. The microbiome was responding to them, too. Even the long-term vegetarian who agreed to eat meat for this study saw a rapid microbial shift.
The microbiome’s dynamic ability to respond to our diet is why our bodies can adapt to so many different ways of eating — regardless of how long it might take for our genes themselves to change. Our genes aren’t what matter — our microbiome’s genes are the key. We don’t have to move at the millennial pace of genetic evolution. We come equipped with a mechanism that is exquisitely responsive to a number of different types of foods, which is why humans all over the world can survive on a remarkably wide range of diets.