Lessons learned from sharing poop: gut microbiota matter

Poop sharing has gotten a lot of (medical) attention in the past few years. Fecal microbiota (or stool) transplants are emerging as the most promising treatment for Clostridium difficile infections, a bacteria that causes large intestine inflammation and is at fault for the majority of chronic indigestion and diarrhea cases worldwide. Hopes for fecal transplantation are so high, and the need for chronic colitis treatment so dire, that impatience with the slow progress of clinical studies has inspired a robust DIY movement and a willing to pay top dollar for your fecal donations.

However, suddenly altering the bacterial makeup of your gut – even if it’s to get rid of nasty Clostridium difficile – may have far reaching and unintended consequences. Recently, a woman reportedly became uncontrollably obese following fecal transplantation. This is actually not particularly surprising. Studies have previously shown that there are discernible differences in the makeup of gut microbiota between lean and obese individuals, and that the microbiota from obese people (when transplanted into mice) will make the mice obese. It’s possible that obesity of her donor could have caused her own subsequent weight gain.

Ultimately, cases like this woman highlight how much we still don’t know about acutely altering our gut microbiota. What is becoming increasingly clear is that the precise microbial makeup of the fecal transplant matters a great deal, but we don’t yet know how to identify or screen for ideal donors.

Special thanks to Daria Van Tyne, a post-doctoral fellow with the Gilmore Lab at Harvard Medical School. Edited by SITN Waves Correspondent Shay Neufeld.