I read a fascinating article the other day about microbes and our relationship with them.
http://www.newsweek.com/id/57368/page/3
Here's the part that got me thinking though:
| QUOTE |
| Microbes play an important role in digestion, especially of polysaccharides, starch molecules found in foods such as potatoes or rice that may be hundreds or thousands of atoms long. The stomach and intestines secrete 99 different enzymes for breaking these down into usable 6-carbon sugars, but the humble gut-dwelling Bacterioides theta produces almost 250, substantially increasing the energy we can extract from a given meal. Of course, "energy" is another way of saying "calories." Jeffrey Gordon of Washington University raised a colony of mice in sterile conditions, with no gut microbes at all, and although they ate 30 percent more food than normal mice they had less than half the body fat. When they were later inoculated with normal bacteria, they quickly gained back up to normal weight. "We are finding that the nutritional value of food is pretty individualized," Gordon says. "And a big part of what determines it is our microbial composition." We can't raise humans in sterile labs, of course, but there's evidence that variations between people in their intestinal microbes correspond to differences in body composition. And other factors appear to be at work besides the ability to extract calories from starch. Bacteria seem able to adjust levels of the hormones ghrelin and leptin, which regulate appetite and metabolism. Certain microbes even seem to be associated with a desire for chocolate, according to research by the Nestlé Research Center. And a tiny study suggests that severe emotional stress in some people triggers an explosion in the population of B. theta, the starch-digesting bacteria associated with weight gain. That corresponds to folk wisdom about "stress eating," but it is also a profoundly disturbing and counterintuitive observation that something as intimate as our choice between a carrot and a candy bar is somehow mediated by creatures that are not us. |