Fiber bulks, speeds, and dilutes the intestinal waste stream to facilitate the removal of excess cholesterol from our bodies, as described in my video Nuts and Bolts of Cholesterol Lowering. This mechanism is similar to how “normal” levels of fiber consumption (huge by modern standards) relieve the body of excess estrogen . Fiber also helps improve intestinal transit time (Stool Size Matters!) and protects against diverticulosis.
Fiber is one of the reasons why nut consumption is associated with lower cholesterol levels (see my last post Cholesterol Lowering in a Nut Shell). Another reason may be phytosterols. The ability of phytosterols in plant foods to reduce cholesterol levels was first reported more than 80 years ago. The same trash-picker analogy used to explain the effects of fiber on cholesterol in the video above can help us understand how phytosterols work. Just as phytoestrogens in plants can have an anti-estrogenic effect by fooling your body into trying to use them instead of your own estrogen–which is a thousand times stronger, phytosterols are plant-based cholesterol look-alikes found predominantly in nuts and seeds. See my 2-min. video How Phytosterols Lower Cholesterol for an illustration comparing the two.
When we eat nuts and seeds, phytosterols progress through our ever-flowing waste stream where the trash-picking cells lining our gut throw them into their bins along with the actual cholesterol molecules. Their bins can only hold so much, though, before they have to go empty it into the body before coming back to the banks of our fecal flow. Thus, if there’s just cholesterol in the waste stream, that’s what fills up the bin, but if there’s phytosterols too then half the bin may be filled with cholesterol and half with phytosterols. This leaves the other half’s worth of cholesterol to flush out to sea.
It’s only once the phytosterols are absorbed that our body realizes the mistake it’s made and dumps them back down the trash chute. Trash pickers further down the line may accidently pick them back up again and repeat the process. In the end (or out the end!), because we swallowed all those phytosterols into our gut, less excess cholesterol gets reabsorbed and, instead, ends up getting dumped.
In my 2-min. video Optimal Phytosterol Dose I show that there’s a plateau effect, though. The cholesterol-blocking effects of phytosterols max out at around 2000 mg, but most people have a long way to go to reach that. The standard American diet may provide as few as 78mg per day. Plant-based diets provide the most phytosterols; nonetheless, there’s still room to improve. Those who have bettered their diet so much that they’re no longer eating any cholesterol should be acing their cholesterol tests, but, in rare cases in which your body might not be able to get rid of enough self-made cholesterol, what is the best source of phytosterols?
In my 2-min. video Optimal Phytosterol Source I note the irony that phytosterols are typically prescribed in butter-form, fortified spreads such as Benecol. Studies show that smaller more frequent doses may be more effective than one big dose in a spread or pill. This makes sense given the trash-picker analogy. We want to have phytosterols constantly flowing through our gut throughout the day so they‘ll continue to keep stuffing the bins of our intestinal lining cells, causing excess cholesterol to pass.
Another reason that phytosterol supplements may not work as well is that we need fat to optimally absorb phytosterols. That’s why they package them into margarine spreads, yet nature put phytosterols right where we need them–in nuts and seeds that have more than enough fat. There now exists phytosterol-fortified orange juice and lemonade, but like the pills, we would not expect phytosterols to be as effectively absorbed due to the lack of fat. The best source of phytosterols is whole plant foods: seeds provide the most—especially sesame (see the chart here), then nuts—especially pistachio, then legumes such as peanuts.
-Michael Greger, M.D.
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Image credit: Satoru Kikuchi / Flickr