The microbiota inside you

Say Hello to the Bugs in Your Gut

Excerpts:

From an early age, the human body is home to a huge but ever-changing community of microbes: for each one of our cells, there are 10 microbial cells in or on the body. Most of them live in the intestines; the bulk of the rest inhabit the mouth, esophagus, stomach, upper airway, skin and vagina. No one knows how many different species coexist inside the human gut. In the first comprehensive census of the gut, David Relman and his colleagues at Stanford University quit counting after they hit 395 different species in three healthy subjects. The real cast of characters will almost certainly number in the thousands.


Curiously, we don't start life with such a microbial partnership. A developing baby floats in sterile amniotic fluid, protected from bumps—and bugs. That isolation ends during the baby's trip through the birth canal, which is a haven for bacteria. The baby picks up microbes on his or her skin; some get into the mouth. From then on, helpful microbes somehow convince the immune system that they mean no harm. They settle down in hospitable regions, and crowd out those that can't compete.
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What's indigestible to you is a seven-course meal to your gut microbiota. The conditions in the colon—dark, moist and free of oxygen—are just what your gut microbiota needs to ferment indigestible material passed on from the small intestine and produce simple sugars and short, chain-free fatty acids. They do this for their own good, but they also share some of these energy-rich substances with their host—us. Some people get up to 10 percent of their daily calories from substances produced by their gut bugs.
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The energy content of food isn't a fixed quantity. Consider the 110 calories per cup listed on a box of Cheerios. Some people may get that much, others may get less, depending on their gut microbiota. A difference of just 25 calories a day—that's half a rice cake or one chocolate kiss—between what you take in and what you burn could mean a gain or loss of more than two pounds in a year and 20 pounds over a decade.

Comment: Very interesting article!