Doctors aren’t entirely sure what triggers rheumatoid arthritis, a disease in which the body turns on itself to attack the joints, but an emerging body of research is focusing on a potential culprit: the bacteria that live in our intestines.
Several recent studies have found intriguing links between gut microbes, rheumatoid arthritis, and other diseases in which the body’s immune system goes awry and attacks its own tissue.
A study published in 2013 by Jose Scher, a rheumatologist at New York University, found that people with rheumatoid arthritis were much more likely to have a bug called Prevotella copri in their intestines than people that did not have the disease. In another study published in October, Scher found that patients with psoriatic arthritis, another kind of autoimmune joint disease, had significantly lower levels of other types of intestinal bacteria.
This work is part of a growing effort by researchers around the world to understand how the microbiome—the mass of microbes that live in the gastrointestinal tract—affects our overall health. The gut contains up to a thousand different bacteria species, which together weigh between one and three pounds. This mass contains trillions of cells, more than the number of cells that make up our own bodies. Over the past several years, scientists have compiled a growing collection of evidence that many of these bugs may have a major effect on our well-being, with some triggering chronic, non-infectious ailments such as rheumatoid arthritis, and others protecting against such diseases.