Probiotics: Microbes on the Menu?
People receive prescriptions for them and even buy foods filled with them, purportedly to restore the natural balance of their gut flora. But the jury is still out on how, and how well, probiotics work.
Probiotics have been around for thousands of years, in traditional fermented foods such as yogurt, sauerkraut and kefir, all of which teem with colonies of microbes. Yet probiotics—by the World Health Organization’s definition, “live microorganisms which, when administered in adequate amounts, confer a health benefit on the host”—have moved from the fringes to the mainstream only in the past decade or so.
A walk down the supermarket dairy aisle reveals an array of yogurts and dairy-based drinks containing “live and active cultures” of bacteria that supposedly bolster health and digestion. In the supplements aisle, consumers can choose from capsules, powders and liquids that contain a wide variety of microbes. But what effect do they really have on our health?
The global probiotics market, which yielded $15.9 billion in 2008, is expected to nearly double by 2014, thanks in part to the many physicians who regularly recommend probiotic supplements during and after a course of antibiotics to help prevent the diarrhea that sometimes accompanies antibiotic-induced die-off of normal gut microbes. Some studies have shown that certain strains of commercially available probiotics positively affect immune response and can protect against infection and diarrhea. Most of the studies, however, have been small, and many have been conducted on mice, so scientists caution against drawing blanket conclusions about probiotics’ effects. And while probiotics don’t have side effects for most people, they can exacerbate problems in certain groups of patients.
Though researchers agree that probiotics likely help in some way, they emphasize that we’re far from understanding their mechanisms. Researchers hope that the advent of more advanced genetic sequencing technology will shed light on what happens to our gut microbiota when we ingest probiotics.