Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

“Virtually every day, we are all confronted with the activity of our intestine, and [it’s] no surprise that at least some of us have developed a fascination for our intestinal condition and its relation to health and disease.”

“Over the last years, the intestinal microbiota [our gut flora] have been identified as [like] a fascinating ‘new organ’” with all sorts of functions. Well, if the bacteria in our gut make up like a whole separate organ inside our body, what about doing an organ transplant?

What would happen if you transferred intestinal bacteria from lean people into obese people? Researchers figured that “rebalancing the [obesity-causing] bacteria” with an infusion of gut bacteria from a lean person might help. Now, they wanted this to be a placebo-controlled study, which for drugs is easy: give a sugar pill. But, when you’re sticking a tube down people’s throats and transplanting feces, I’m thinking, what do you use as a poop placebo—a poopcebo, if you will? Both the donors and the subjects brought in fresh stools, and the subjects were randomized to either get the donor stool, or get transplanted with their own collected feces. That was the placebo; you get your own back.

Okay. So, what happened? The insulin sensitivity of the skinny donors was up around 50; that’s a good thing. High insulin sensitivity means low insulin resistance—the cause of both type 2 diabetes and prediabetes. The obese subjects started out around 20, and after an infusion of their own feces, they stayed around 20. But, the group of obese donors getting the skinny similarly started out low, but shot up to near where the slim folks were.

It’s interesting; not all lean donor stools conveyed the same effect on insulin sensitivity, as some donors had very significant effects—the so-called super-fecal donor, whereas others had little or no effect. Turns out this “super-donor effect” is most probably conveyed by the amounts of short-chain fatty acid-producing intestinal bacteria in their feces, the food bacteria that thrive off of the fiber we eat. The short-chain fatty acids produced by fiber-eating bacteria may contribute to the release of gut hormones that may be the cause of this beneficial improved insulin sensitivity.

“The [successful] use of fecal transplantation has recently attracted considerable attention,” not only because of its success, but its capacity to prove the cause and effect relationship—that the bacteria we have in our gut can affect our metabolism. But, within a few months, the bacterial composition returned back to baseline; so, the effects on the obese subjects were temporary.

We can get similar benefits, though, by just feeding what few good gut bacteria we may already have. Say you have a shed full of bunny rabbits. Feed them pork rinds, and they all die. Yes, you can repopulate your shed by infusing new bunnies, but if you keep feeding them pork rinds, they’ll eventually die off as well. Whereas, even if you start off with just a few bunnies, if you feed them what they’re meant to eat, they’ll grow and multiply, and soon, you’ll be full of fiber-eating bunnies.

Fecal transplants and probiotics are only temporary fixes, if we keep putting the wrong fuel into our gut. But, by feeding prebiotics, such as fiber, which means “increasing whole plant food consumption,” we may select for, and foster the growth of, our own good bacteria.

However, such effects may abate once the high-fiber intake ceases. Therefore, our dietary habits should “include a continuous consumption of large quantities of high-fibre foods” to improve our health. And, if we don’t, we may be starving our microbial self.

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