Image Credit: Taylor McConnell / Flickr. This image has been modified.

Stool Size and Breast Cancer Risk

Women eating plant-based diets may have lower breast cancer rates because they have larger bowel movements. In The Best Detox, I described the role of the liver in removing toxins from the blood stream, which can then be jettisoned through the bile into the digestive tract, and eliminated. Our gut is our body’s disposal system; anything it wants to get rid of, it throws down the trash chute. One 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 garbage flowing past and picking up anything of use—a vitamin here, a mineral there, such that by the end there isn’t much left that’s desirable—and what’s left truly gets, ahem, dumped.

The digestive tract is also how we get rid of excess hormones and cholesterol. Our body expects there to be an ever-flowing torrent of intestinal contents to flush this stuff out to sea. We did, after all, evolve over millions of years on a diet centered on unrefined plant foods. We aren’t designed for burgers and milkshakes; we are designed for fiber, and lots of it.  Anthropologists estimate we evolved eating 100 grams of fiber a day or more!

So our body is counting on a massive, quick-flowing stream of contents through our digestive tract, and when there’s excess estrogen in the trash, our body expects it to just zip right out. But what if we don’t consume an adequate amount of fiber to soften and bulk up that intestinal flow? What if that river dries up into just a slow trickle of sludge? We still have the same number of trash pickers, but the volume and speed of the flow is way down, so they’re finding all sorts of stuff that otherwise would have been lost. Uh oh—that means they’re picking back up the estrogen that your body intentionally dumped, and thrusting it right back into the system. Fiber, on the contrary, dilutes, speeds, and bulks up the flow, so lots of stuff never even makes it to banks of the river to be picked at and inappropriately saved. My 4-min video Relieving Yourself of Excess Estrogen explains that this may be why women who eat lots of plants (the only place fiber is found) have lower estrogen levels and a lower risk of breast cancer.

As I show in my 1-min video Food Mass Transit, meat-eating women average a four-day mouth-to-anus transit time, likely too long to meet the target 200 gram (half pound) minimum fecal output for cancer prevention. People don’t realize you can have daily bowel movements and still be effectively constipated. You can be regular, but four days late. In other words, what you’re flushing today you may have eaten last week. If you want to test it for yourself, all you need to do is eat a big bowl of beets and see when things turn pretty in pink. Ideally, to reach that half-pound target, your intestinal transit time should be down in the 24 to 36 hour range.

Small bowel movements are also associated with a variety of other diseases such as appendicitis, colon cancer, constipation, and diverticulitis. See my 2-min. video Stool Size Matters. Just eating antioxidant-rich foods can improve stool weight. See Bulking Up on Antioxidants (2 min). And finally, check out Bowels of the Earth (2 min) to find out which country has the largest (and smallest) average stool size. Find out who’s #1 at number 2!

-Michael Greger, M.D.


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

6 responses to “Stool Size and Breast Cancer Risk

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  1. Very Informative article, I like how you described it in a easy language. Moreover breast cancer is a very common and dangerous problem now a days. I’ve seen it is fast growing in USA, more and more social awareness should be increased in this regard like conferences, seminars, group talk, advertisement etc. So that it could be cured at grass root level.
    Maria @ buydianaboluk

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