Fiber bulks, speeds, and dilutes the intestinal waste stream to facilitate the removal of excess cholesterol from the body.
How Fiber Lowers Cholesterol,
We’ve covered a bunch of ways nuts may cut heart disease risk, boosting nitric oxide production in our arteries because the arginine content in nuts, cutting down our risk of sudden cardiac death because of the magnesium content, and lowering 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 parts can be absorbed. We can imagine our enterocytes, the cells lining our intestinal wall, as 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 desireable and truly gets dumped.
So our gut is our bodies’ 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 your liver makes as much as it needs. If you 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’s an everflowing torrent to flush it out to sea. We did, afterall, evolved for millions of year 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. 100 grams a day or more. A massive, quick-flowing stream. And so when your body throws some cholesterol down the trash chute it knows its going to zip right out, but what if the river dried 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, and 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 ever even make it to the banks of the intestinal river to be picked at 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.
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This mechanism is similar to how "normal" levels of fiber consumption (huge by modern standards) relieve the body of excess estrogen, which may explain reduced breast cancer risk in those eating plant-based diets. Fiber also helps improve intestinal transit time (stool size matters!) and protects against diverticulosis. An explanation of the nitric acid 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, and Friday's video-of-the-day Nuts and Bolts of Cholesterol Lowering covered the cholesterol angle. The next two follow-up videos will use the same trash-picker analogy to explain the actions of phytosterols. If you haven't yet, you can subscribe to my videos for free byclicking here.
For more context, check out my associated blog post, Stool Size and Breast Cancer Risk.