About that gut feeling

More news on the microbiome. As I explained in my post about bacterial crowdsourcing, each and every one of us hosts about 100 trillion microbes in and on our bodies. This population is known as the “human microbiome.” They’re everywhere – armpits, butt cracks, skin, nostrils… and guts. Our guts alone harbor more than 1000 different kinds of bacteria.

The microbiome is a very hot area of research right now, and rightly so, in my opinion. The US National Institutes of Health is pouring money into the Human Microbiome Project in much the same way they funded the Human Genome Project starting in 1990. Understanding our own cells isn’t enough, see, cuz guess what? All those critters probably aren’t just sitting there doing nothing.

Recent research bears this out. A team from University College Cork recently reported on research in which they fed mice probiotic bacteria for six weeks and then observed their behavior.  The mice receiving the probiotics exhibited fewer signs of stress and anxiety. They spent more time exploring nerve-wracking places like elevated walkways and had a smaller spike in their stress hormones when placed in water, another really scary mouse experience. Lead researcher John Cryan was psyched:

“This was really exciting because it tells us the animals are more chilled out and don’t mount the same stress response.”

Even more interesting is that when the researchers cut the vagus nerve (which connects the nerve cells in the gut with the brain), all these beneficial effects vanished. The probiotics aren’t affecting the brain chemistry directly, they’re affecting the gut chemistry, which then gets transmitted somehow to the brain.

Jonah Lehrer wrote about the research in the WSJ, “The Yogurt Made Me Do It.” He proved once again why he’s my all-time favorite science writer by focusing on the study’s philosophical implications. Most of us “feel” like our minds are different than our bodies. But if we extrapolate from that mouse study and assume the premise might also hold true with humans, then what we’ve got in our guts affects how we feel, and how we experience the world. You should really read the whole article, but here are a couple juicy snippets if you don’t have time:

There’s nothing metaphorical about “gut feelings,” for what happens in the gut really does influence what we feel.

This research shows that the immateriality of mind is a deep illusion. Although we feel like a disembodied soul, many feelings and choices are actually shaped by the microbes in our gut and the palpitations of our heart. Nietzsche was right: “There is more reason in your body than in your best wisdom.”

In another piece of recent research, scientists show that antibiotics can permanently destroy some species of our gut flora. Maryn McKenna writes about it in her Wired blog Superbug. We’ve evolved along with our microbiome in a lovely symbiotic adaptation that’s gone on over countless millenia. Are we eradicating all that hard work in just two generations by flagrantly overtreating common, non-life-threatening infections?   Connect these two pieces of research and see what you get. Good gut bacteria = good mental health. Antibiotics kill gut bacteria permanently. Depressed, anyone? Stressed? My question: can yogurt offset this? Are my children going to spend years in therapy or pop Prozac for the rest of their lives because of all that pink antibiotic they swallowed when they were babies? Is the whole thing just a Big Pharma Plot?

As I dug through these fascinating bits of evidence of the microbiome’s importance in human health, I ran across yet another connection. Last June, NewScientist magazine reported on research that found that autistic children had a different “gut bacteria signature” in their urine than normal children.

“It adds another link to the gut bacterial involvement in the onset of disorder,” says Glenn Gibson of the University of Reading, UK, who has previously identified abnormally high levels of clostridium bacteria in children with autism.

One possibility is that the gut bacteria in children with autism are producing toxins that might interfere with brain development. One of the compounds identified in the urine of autistic children was N-methyl-nicotinamide (NMND), which has also been implicated in Parkinson’s disease.

They were hopeful that this could be used as a sort of diagnostic tool, in the hope that addressing the problem earlier, even before behavioral traits showed up, would be beneficial. I hope they go further than this, and try and figure out a way to restore the health or these kids’ gut microbiomes, rather than just help them cope with the effects of toxic ones.

All this research illustrates that the gut microbiome plays a critical role in far more than just our gastrointestinal health.  I already wrote about the possibility that the microbiome very likely plays a role in cancer. It’s a good thing that we’re broadening scientific inquiry beyond the limited scope of the human genome. There’s a whole lot more in our navels (and our breakfasts) that merits a good, long gaze.

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