Washington Post
by Rob Stein
9 Oct 11

Consider this: The average person’s body contains about 100 trillion cells, but only maybe one in 10 is human.

….

That thought might make a lot of people lunge for the hand sanitizer, at the least. But that predictable impulse may be exactly the wrong one. A growing body of evidence indicates that the microbial ecosystems that have long populated our guts, mouths, noses and every other nook and cranny play crucial roles in keeping us healthy.

Moreover, researchers are becoming more convinced that modern trends — diet, antibiotics, obsession with cleanliness, Caesarean delivery of babies — are disrupting this delicate balance, contributing to some of the most perplexing ailments, including asthma, allergies, obesity, diabetes, autoimmune diseases, cancer and perhaps even autism.

….these microbial stowaways may wield far greater powers than previously appreciated in, paradoxically, making us human.

….known as the “microbiome” or “microbiota.”

….Some equate these microbial inhabitants to a newly recognized organ.

….There are even tantalizing clues they may help shape brain development, influencing behavior.

….“There’s been a real revolution in thinking about what that means.”

….European scientists reported in April that people generally seem to have one of three basic combinations that may be as fundamentally important as, say, blood type.

….

Intriguing clues are also emerging about how microbes may affect the brain. Manipulating gut microbiomes of mice influences their anxiety and activity, Swedish researchers reported in January in the Proceedings of the National Academy of Sciences.

"This may have implications for new lines of thinking to address some of the psychiatric problems you see among humans," said Sven Pettersson, a professor of host-microbial interaction at the Karolinska Institute. "Together with genetic susceptibility, this may influence what doctors classify as autism or ADHD."

In another experiment involving mice, a Canadian-Irish team reported in August that bacteria in the gut appear to influence brain chemistry, and corresponding behaviors such as anxiety, stress and depression, via the vagus nerve….


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