The old adage that “you are what you eat” is especially true when you bring your gut microbes into the picture.

Your guts are home to trillions of bacteria and other microbes, which outnumber your own cells by ten to one. This microbiome—the collective term for the microbes and their genes—helps to break down the food you eat, among many other important roles. It’s like one of your organs, albeit one made of legions of swarming cells, none of which are human.

It can also change… and fast.

By setting ten volunteers on either a vegetarian menu or a carnivorous one, Lawrence David from Duke University and Harvard University’s Peter Turnbaugh have shown that when our diet changes, our gut bacteria react