"Should I start taking a probiotic? I see them advertised as a cure for everything!"
Let me start by saying that the science around the human microbiome (organisms that live in or on the human body) is evolving rapidly, and I predict that this discipline will become very much front line in the next decade.
We all have a particular and very complex intestinal microbiome. The theory behind the ingestion of probiotics is that by taking them, you may realize the benefits imparted by the bacteria in the preparation, or that you may recolonize your colon with more "healthy" bacteria. Studies have demonstrated relationships between obesity and the preponderance of certain microbes, which in turn strongly suggests a relationship between obesity and the microbiome. However, there are not yet good randomized controlled trials that demonstrate consistent reproducible effects between probiotics and weight loss. Data from animal studies and small human studies also suggests that there may be links between the microbiome and inflammatory diseases, depression and other diseases.
The problem with taking probiotics is that most of us don't know the composition of our current microbiome to begin with. The unknowns are further compounded by the lack of good studies with probiotics in humans. For example, do the bacteria in a particular formulation even survive the trip to the colon and even if they do, what bacteria do you, as an individual, actually need? On the other hand, although quite expensive, probiotics appear to be quite safe.
A more natural way of providing yourself with probiotics may be via fermented foods — sauerkraut, yogurts and kefir with active cultures — and by eating high fiber foods that may provide support for your existing microbiome.
John R. White is chair for the Department of Pharmacotherapy in the College of Pharmacy at WSU-SPokane and the author of two books.