How Fiber Lowers Cholesterol

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Fiber bulks, speeds, and dilutes the intestinal waste stream to facilitate the removal of excess cholesterol from the body.

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We’ve covered a bunch of ways nuts may cut heart disease risk—boosting nitric oxide production in our arteries because of the arginine content in nuts; cutting down our risk of sudden cardiac death because of the magnesium content; and lowering the risk of our bad cholesterol because of…why, exactly? How do nuts lower our cholesterol? What are the “potential mechanisms?”

This is where it gets a little complicated. These may be the various nutrients responsible for bad cholesterol reduction. Let me just touch on two—first, fiber; then, phytosterols.

What’s flowing through our intestines right now is going to end up as waste. That’s the default, unless any bits can be absorbed. We can imagine our enterocytes—the cells lining our intestinal wall—as a vast array of trash pickers; resource recovery workers. They’re sifting through the river of potential garbage flowing past, and picking up anything of use—a vitamin here, a mineral there, such that by the end, there really isn’t much left that’s desirable and truly gets dumped.

So, our gut also acts as our body’s disposal system. Anything it wants to get rid of, it throws down the trash chute—like excess cholesterol.

Cholesterol plays a vital role in the body, and that’s why our liver makes as much as we need. But if our liver feels there’s just too much cholesterol circulating around, it dumps the excess into the gut to get rid of it—knowing full well there’ll be an everflowing torrent to flush it out to sea.

We did, after all, evolve for millions of years on a plant-based diet, like our great ape ancestors. And so, we weren’t designed for burgers and milkshakes; we were designed for fiber, and lots of it. A hundred grams a day, or more. A massive, quick-flowing stream.

And so, when our body throws some cholesterol down the trash chute, it knows it’s going to zip right out. But, what if our river dries up—just a slow trickle of sludge, because we’re not eating enough whole plant foods? We still have the same number of trash pickers, but the volume and speed of the flow is way down on a fiber-deficient diet.

So, they’re finding all sorts of stuff that otherwise would have been lost. So, they’re picking back up estrogen that our body dumps; cholesterol; and putting it right back into the system.

It’s like if you litter, and someone comes by and picks it up and says, “Excuse me; did you drop that?” Fiber bulks up the flow, speeds it up, and dilutes everything, so lots of stuff may never even make it to the banks of the intestinal river to be picked up and inappropriately saved.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Kerry Skinner.

Please consider volunteering to help out on the site.

Images thanks to RedAndr via Wikimedia; Cindi PierceRenee CometNational Cancer Institute; and Gastrolab.

We’ve covered a bunch of ways nuts may cut heart disease risk—boosting nitric oxide production in our arteries because of the arginine content in nuts; cutting down our risk of sudden cardiac death because of the magnesium content; and lowering the risk of our bad cholesterol because of…why, exactly? How do nuts lower our cholesterol? What are the “potential mechanisms?”

This is where it gets a little complicated. These may be the various nutrients responsible for bad cholesterol reduction. Let me just touch on two—first, fiber; then, phytosterols.

What’s flowing through our intestines right now is going to end up as waste. That’s the default, unless any bits can be absorbed. We can imagine our enterocytes—the cells lining our intestinal wall—as a vast array of trash pickers; resource recovery workers. They’re sifting through the river of potential garbage flowing past, and picking up anything of use—a vitamin here, a mineral there, such that by the end, there really isn’t much left that’s desirable and truly gets dumped.

So, our gut also acts as our body’s disposal system. Anything it wants to get rid of, it throws down the trash chute—like excess cholesterol.

Cholesterol plays a vital role in the body, and that’s why our liver makes as much as we need. But if our liver feels there’s just too much cholesterol circulating around, it dumps the excess into the gut to get rid of it—knowing full well there’ll be an everflowing torrent to flush it out to sea.

We did, after all, evolve for millions of years on a plant-based diet, like our great ape ancestors. And so, we weren’t designed for burgers and milkshakes; we were designed for fiber, and lots of it. A hundred grams a day, or more. A massive, quick-flowing stream.

And so, when our body throws some cholesterol down the trash chute, it knows it’s going to zip right out. But, what if our river dries up—just a slow trickle of sludge, because we’re not eating enough whole plant foods? We still have the same number of trash pickers, but the volume and speed of the flow is way down on a fiber-deficient diet.

So, they’re finding all sorts of stuff that otherwise would have been lost. So, they’re picking back up estrogen that our body dumps; cholesterol; and putting it right back into the system.

It’s like if you litter, and someone comes by and picks it up and says, “Excuse me; did you drop that?” Fiber bulks up the flow, speeds it up, and dilutes everything, so lots of stuff may never even make it to the banks of the intestinal river to be picked up and inappropriately saved.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Kerry Skinner.

Please consider volunteering to help out on the site.

Images thanks to RedAndr via Wikimedia; Cindi PierceRenee CometNational Cancer Institute; and Gastrolab.

Doctor's Note

This mechanism is similar to how “normal” levels of fiber consumption—huge by modern standards—relieve the body of excess estrogen (see Relieving Yourself of Excess Estrogen), which may explain reduced breast cancer risk in those eating plant-based diets. Fiber also helps improve intestinal transit time; see Food Mass Transit, and Stool Size Matters. It also protects against diverticulosis; see Diverticulosis & Nuts. An explanation of the nitric oxide effect can be found in The Power of NO, and the magnesium data is in How Do Nuts Prevent Sudden Cardiac Death? and Mineral of the Year: Magnesium. The cholesterol angle is covered in Nuts and Bolts of Cholesterol Lowering. Both Optimal Phytosterol Dose and Optimal Phytosterol Source use the same trash-picker analogy to explain the actions of phytosterols.

For more context, check out my associated blog posts: Stool Size and Breast Cancer Risk and Treating Parkinson’s Disease with Diet.

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