The Most Potent Phytoestrogen Is in Beer

Why do alcoholic men develop man boobs, and other feminine traits? Well, we know estrogens produce feminization, and our liver clears estrogens from the body. And so, the original theory was alcohol-induced liver damage leading to the retention of excess estrogens. The problem was that when they measured estrogen levels, they were not elevated. And even those with cirrhosis of the liver appeared to clear estrogens from the body normally. And also, men’s testicles started shrinking, even before serious liver disease developed.

So, alternative explanations were considered. Well, if it’s not due to estrogens produced endogenously, meaning within the body, maybe alcoholics are being exposed to exogenous estrogenic substances from dietary sources—maybe from phytoestrogens in the plants that alcoholic beverages are made from.

The discovery that plants could contain hormonal compounds was made back in 1951 by two Australian chemists charged with finding out the cause of an epidemic of infertility in sheep that was ravaging their nation’s wool industry. It took them ten years, but they finally figured out the cause—a compound present in a type of clover called genistein, the same phytoestrogen found in soybeans.

Online, you can read about the dreaded clover disease on scare-mongering websites, but you’ll note they never talk about the difference in dose. To get as much as the sheep were getting from clover, you’d have to drink more than a thousand cartons of soy milk a day, eat 8,000 soy burgers, or about 800 pounds of tofu a day.

This is not to say you can’t overdo it. There are two case reports in the medical literature on feminizing effects associated with eating as few as 14 to 20 servings of soy foods a day. But at reasonable doses, or even considerably higher than the one or two servings a day Asian men eat, soy phytoestrogens do not exert feminizing effects on men.

So, anyways, back in 1951, we realized plant compounds could be estrogenic. Aha, two German researchers realized, maybe that’s why women who handle hops start menstruating. And indeed, they found estrogenic activity in hops, which is the bittering agent used to make beer. They found trace amounts of the soy phytoestrogens, but in such tiny quantities that beer would not be expected to have an estrogenic effect.

But then in 1999, a potent phytoestrogen called 8-prenylnaringenin was discovered in hops—in fact, the most potent phytoestrogen found to date; 50 times more potent than the genistein in soy, an obvious explanation for the menstrual disturbances in female hops workers in the past. Now that we have machines to pick our hops, our only exposure is likely via beer consumption, but the levels in beer were found to be so low, they shouldn’t cause any concern.

But then in 2001, a study on a hops-containing dietary supplement for “breast enhancement” raised the concern that another phytoestrogen in hops, called isoxanthohumol, might be biotransformed by our liver into the more potent 8-PN—which would greatly augment the estrogenic effect of hops. But this was a study done on mice. Thankfully, a study using human estrogen receptors found no such liver transformation.

And so, all seemed fine, until 2005. See, the liver is not the only transformation site inside the human body. The human colon contains trillions of microorganisms with enormous metabolic potential. It’s like a whole separate organ within our body, with a hundred livers’ worth of metabolizing power. So, let’s effectively mix some beer with some poop, and see what happens.

And indeed, up to a 90% conversion was achieved. Up until then, the concentration of 8-PN in beer was considered too low to affect human health. However, these results show that the activity of the intestinal microbial community could more than tenfold increase the exposure concentration. This can explain why you can detect 8-PN in the urine of beer-drinkers for days—because their gut bacteria keep churning it out. Obviously, the amount of straight 8-PN in beer is not the only source of estrogen effects, given this conversion.

So, a decade ago, the question remained, might drinking too much beer cause estrogenic effects and feminize men? I’ll give you the ten-year update in my next video.

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 Katie Schloer.

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Image thanks to Enokson via flickr.

• alcohol
• animal studies
• Asia
• beer
• beverages
• breast health
• cirrhosis
• estrogen
• gut flora
• liver health
• microbiome
• phytoestrogens
• soy
• soy milk
• tofu
• women's health