There's an extra organ in your body you may not have known about, and it's made out of bugs - microbes, that is, and there are about ten times as many of them as there are human cells in your entire body.
Each of us, if healthy, is carrying around on the order of 1,000 different species of microbes in his or her gut - a vast internal ecosystem, easily rivaling a rainforest in the interdependent complexity of its resident species.
As Stanford microbiologist Justin Sonnenburg, PhD, co-author of this neat article in the journal Science Translational Medicine, points out, these bugs work together as a community, and they're largely working for us: helping us digest our food, fending off invading pathogens, secreting critical nutrients such as vitamins, even performing tasks critical to the development of our own tissues. You wouldn't want to try living without them.
At present, the probiotic movement is in its infancy, Sonnenburg and his co-author Michael Fischbach, PhD, of UCSF point out. Several clear associations have been made between the presence or absence of specific microbes, or collections of them, in our gut and states of health or disease. One species protects us from kidney stones, another from E. coli infection.
Still, little is known about what the vast majority of our inner ecosystem's inhabitants do - and less is known about how they do it. Currently, dietary substances labeled probiotics are classified as foodstuffs, so they're essentially unregulated. There's no guarantee that what's in there is what the label says is in there, that it's alive, or that it will establish a toehold in the strange new country that is your intestine - and each of ours is at least a little bit different. For the most part, the microbial species in yogurt or other fermented foods aren't identical to the ones normally living inside us, although they may nonetheless be beneficial.
Sonnenburg has also shown that dietary changes (for example, supplementation with specialized sugars such as inulins) can alter the composition of our gut flora.
Sonneburg's article proposes that by learning more details of what, exactly, these bugs are up to individually and collectively - something he's got a very sophisticated way of doing - we may get to the point someday where the pills we take will contain microbes instead of molecules:
Imagine taking a daily probiotic pill that contains four bacterial strains: The first one synthesizes and excretes a cholesterol-lowering drug and a cocktail of vitamins; the second one neutralizes carcinogenic free radicals and consumes dietary cholesterol and fat; the third one modulates your immune system to ward off infection and hold autoimmune disease in check; and the fourth one produces an appetite-suppressing compoind, and anti-depressant, and a cognitive enhancer.
It's possible that warding off infection, cancer, obesity or autoimmune disease may someday be a matter of mixing up a potion of medicinal microbes.
Photo by juhansonin