Prebiotics are a kind of fiber that is indigestible by the human body, but can act as food for our microbes. They are present in fiber rich foods like fruits, vegetables and whole grains. Probiotics are live microbes that are supposed to confer some kind of a health benefit to our microbiome. They are typically found in many fermented foods like yogurt, kefir and sauerkraut.
Both prebiotics and probiotics are sold as dietary supplements and often make wide (and often unsubstantiated) claims of health benefits. However, the food supplement business is barely regulated and so far even the best clinical trials of these treatments are limited and short-term. This makes their use confusing for everyone, both users and doctors.
There are a bewildering number of prebiotic and probiotic products out there. But there are some early indicators that some probiotics are effective for treating some conditions. There is some promise for the treatment of IBS and asthma and for antibiotic-associated diarrhea or traveler’s diarrhea. The two clinical guides below (for the USA & Canada) can help. They show which probiotics have been tested in randomized and clinical trials and provide information by age and disease.