Gut microbiome may dwindle over generations of low fiber diets.

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http://medicalxpress.com/news/2016-01-lo...n-gut.html.   "The study, conducted in mice, indicates that low-fiber diets not only deplete the complex microbial ecosystems residing in every mammalian gut, but can cause an irreversible loss of diversity within those ecosystems in as few as three or four generations.
Once an entire population has experienced the extinction of key bacterial species, simply "eating right" may no longer be enough to restore these lost species to the guts of individuals in that population, the study suggests. Those of us who live in advanced industrial societies may already be heading down that path.
The proliferation of nearly fiber-free, processed convenience foods since the mid-20th century has resulted in average per capita fiber consumption in industrialized societies of about 15 grams per day. That's as little as one-tenth of the intake among the world's dwindling hunter-gatherer and rural agrarian populations, whose living conditions and dietary intake presumably most closely resemble those of our common human ancestors, said Justin Sonnenburg, PhD, associate professor of microbiology and immunology and senior author of the study, to be published Jan. 13 in Nature."

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Some time ago (I can't even remember whether or it was less or more than a decade), the "mainstream" medical consensus seemed to flip-flop on what had been a trend of promoting fiber as a preventive measure for colon cancer. Not that fiber wasn't good or necessary, but just wasn't what it was cracked-up to be in that specific area. Now I guess they've typically yo-yoed back again propaganda-wise after discovering that there really is at least one chemical agency, more abundant in the tracts of primitive peoples with rich fiber diets, outputted by gut bacteria, which does help prevent such.

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That storyline seems to correspond pretty much with my recollection too.

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High fiber might be a way that people eat low calorie diets because they feel less hungry filling up more with the fiber.  It might not directly be the fiber or improved regularity so much as the lower calories. Yet I have a hunch that being hungry often and for a certain lengh of time is involved more than the amount of calories.


http://medicalxpress.com/news/2016-01-li...ealed.html
"In mice, investigators found that a high caloric diet turned off expression of a key hormone in the intestine, which led to deactivation of a tumor suppressor pathway. Genetic replacement of that hormone turned the tumor suppressor back on and prevented cancer development—even when mice continued to eat excess calories."