Ciorba says that when probiotics first became popular, the FDA was not completely sure how to handle them. “Not only was it a natural product, but it was also a live product. And it was being used in all these different populations to presumably treat diseases,” he says. Now that the FDA is more actively involved, there's better research being done on these supposedly miraculous microbes. But just as there is no such thing as a standard, universal antibiotic that cures all bacterial infections, there is no universal probiotic—no cure-all beneficial bug to fix your gut. It’s going to take a lot of time, effort, and research to figure out what bacterial strains help what conditions, says Ciorba. We may one day be able to design and purchase probiotic strains tailored to fix our problems, but we're not there yet.