15 November 2018

How your gut bacteria may affect your weight and health

Two articles in recent weeks detailed some new and significant findings about the human gut microbiome.  First from NPR:
Moving to the U.S. can seriously mess with immigrants' microbiomes, according to a new study that tracked the digestive health of refugees coming to Minnesota from Southeast Asia. "We found that when people come to the U.S.A., they almost immediately begin losing some of their native microbes," says Dan Knights, a quantitative biologist at the University of Minnesota and the study's senior author. Some of the strains they lose are ones that help them break down and glean nutrients from fibers found in Southeast Asian staples like wild greens, coconut and tamarind...

Among that group of 19 refugees, researchers noticed that a Western bacteria strain called Bacteroides began to displace the non-Western strain Prevotella within their first six to nine months in the U.S. But they lost more microbes than they gained — "so the diversity in their microbial communities decreased," Knights says. "And some of the Prevotella bacteria they lost were the ones that helped them digest fiber from plants and greens."

Some of the bacteria in our guts feed, and survive, on particular fibers found in grains and greens — and die off when they don't get enough. But changes in diet didn't explain all — or even most — of the change in immigrants' microbiomes. "It could be that other factors, like exposure to different medications, especially antibiotics or changes in the quality of water they're drinking, are also affecting their microbiomes...

"In speaking with community members, we also realized that for them, the biggest concern was obesity," says Vangay. "Because they had observed in themselves and their relatives and friends that when they moved to the U.S., they gained a lot of weight. And in some cases, they hadn't really changed too much about their diet."
Fascinating.  Now this from Harvard Magazine:
A. Sloan Devlin, an assistant professor at Harvard Medical School, and her team have discovered that altering a single gene in a single type of bacteria can even change the metabolism of the host organism...

During the 32-day study, the mice that could not process bile, for instance, had more fat in the liver and gained weight much more slowly than the other group. They also used proportionately less fat and more carbohydrate for energy...

“It’s a bacterium,” she points out, “and a single enzyme in a bacterium, that’s causing a change in whether the host is using fats versus carbohydrates.”
Control of body weight used to be conceptually so simple: calories in minus calories expended.  Now it appears to be much more complex than that.

Related: Fecal transplant to treat C. difficile colitis.

7 comments:

  1. This has been recognized for some time but is becoming more known to the public. There's a few companies, like Viome, that will sequence your gut micobiome for you and give you advice on how to change your eating habits based on that. At this point in time this sort of understanding is fairly primitive.

    Here's the really fascinating thing. The number of bacterial cells in your body exceeds the number of human cells in your body by about ten fold. And it likely has a comparable amount of genetic information. One of the jobs of your underated appendix is to help maintain the diversity of the microbiome. So clearly it's useful to be diverse and there's a symbiotic relationship. But the thing that is only getting really started is the realization that viruses in your body may outnumber the bacteria. There is a hypothesis that the viruses are the gate keepers of which bacteria are allowed to survive in the body. Thus even after we conquer the microbiome there's going to be even more to understand about the Virome.

    The bottom line is you are not exactly in control.

    Just to give one example, taxoplasmosis can radically alter behaviors. In rats it creates risk taking and cat-seeking behavior which is pretty contrary to the normal rat behavior. in humans it is believed to change sexual displays and the description of it has been said to make women more attractive and men more meek. It's believed to infect a large fraction of Brazil's population.

    Were basically just a committee of bacteria and a large bag of self propelled virus kibble


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  2. your 'this post' ties in very nicely with your 'next post' about the black carrots.

    I-)

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  3. I want a fecal transplant from the skinniest group of people I can find.

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  4. My son has a chromosomal condition called Prader Willi Syndrome that affects one in every 18,000 live births. The condition means, among other things, means the "full" signals from his hypothalamus don't work. He constantly feels hungry. And the condition also means that he will be on a calorie and carb-restricted diet for his entire life because he can gain weight more easily than an average person. They are also prone to more digestive issues than most people - constipation, trouble with high-fiber diets, etc. The Foundation for Prader-Willi Research (https://www.fpwr.org/) is currently conducting a couple of studies to determine if people with my son's condition have different gut microbiomes than most people... and if changing those gut microbiome species might help with any of the issues they face.

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    1. I'm quite familiar with Prader Willi, but this is the first I've heard of the current research. I encourage readers to support the foundation's efforts; I made a contribution today.

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    2. My son and I thank you!
      https://www.fpwr.org/fpwr-funded-projects/gut-microbiome-in-individuals-with-pws
      https://www.pwsausa.org/pwsa-usa-approves-grant-profiling-gut-microbiome-children-pws/

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    3. Almost forgot this study: https://www.fpwr.org/fpwr-funded-projects/gut-microbiome-prader-willi-syndrome

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