Risks of fecal microbiota transplantation include pathogen transmission and unintended metabolic changes like obesity.

“well I think the biggest risk is you know fundamentally your uh it doesn't feel like a therapeutic to give people so I think there's sort of this Instinct that okay this isn't safe but but there's there is a reality Rena which is that you don't know the the source of that person is is really important right how do you know that that's a healthy so-called healthy stool donor and so what if they've got some weird pathogen that now you put it into this person uh who's already in a compromised um and then furthermore because everybody's microbiomes does do have these different functions it's possible that you might cure them of the CI okay great and you might not have given them a new pathogen that's fine but you might have changed their metabolism of foods in a way that's not beneficial to them and so for example there are some of these uh case studies of someone getting a feal microbiome transplant and now all of a sudden they have obesity issues that they never had before”