The Effects of the Hops Phytoestrogen in Beer on Breast Cancer Risk

Hops have been used for centuries as a flavoring agent in beer, but “[o]ver the years, a recurring suggestion has been that hops”—and therefore beer—may be estrogenic, thanks to a potent phytoestrogen in hops called 8-PN, also known as hopein. Might beer drinking affect our hormones? I discuss this in my video What Are the Effects of the Hops Phytoestrogen in Beer?.

Even just the alcohol in beer can reduce testosterone levels in men, so when beer was tested as a source of estrogens, the alcohol was first removed. Researchers tested the equivalent of one can of beer every day for a month on the hormone levels of postmenopausal women, so as to not confound the results with her own estrogens, and they found significant alterations of hormonal levels during the beer month and then a return to baseline a week afterwards. But does this have any clinical effects, whether good or bad?

A cross-sectional study of about 1,700 women found that beer drinkers appear to have better bone density, perhaps because of the pro-estrogenic effects. They don’t recommend women start drinking beer for bone health, but suggest it may have beneficial bone effects for women who already drink.

What about helping with hot flashes? About half of postmenopausal and premenopausal women in the United States suffer from hot flashes, whereas the prevalence in Japan may be ten times lower, presumed to be because of their soy consumption. What about hops? There have been a few studies showing potential benefit, leading to a 2013 review suggesting that “hop extract may be somewhat effective in treating menopausal discomforts especially against hot flushes,” but that was before a study reported extraordinary results with about a half teaspoon of dried hop flowers. In the placebo group, the women started out having 23 hot flashes a week and continued to have 23 hot flashes a week throughout the three-month study. In the hops group, the women started out even worse with about 29 hot flashes a week, but then got down to 19 at the end of the first month, then 9, and finally just 1 hot flash a week. And similar findings were reported for all the other menopausal symptoms measured.

Animal estrogens work, too. Millions of women used to be on horse hormones—Premarin, from pregnant mares’ urine. That drug also took care of hot flashes, as well as  curtailed osteoporosis, but caused a pesky little side effect called breast cancer. Thankfully, when this was realized and millions of women stopped taking it, breast cancer rates fell in countries around the world.

The question, then, is: Are the estrogens in hops more like the breast cancer-promoting horse estrogens or the breast cancer-preventing soy estrogens? The key to understanding the health-protective potential of soy phytoestrogens is understanding the difference between the two types of estrogen receptors, alpha receptors and beta receptors. Unlike animal estrogen, the soy phytoestrogens bind preferentially to the beta receptors, and in breast tissue, they’re like yin and yang with the alpha receptors signaling breast cell proliferation. This explains why horse hormones increase breast cancer risk, whereas the beta receptors, where the soy binds, oppose that proliferative impact. So, do the hops phytoestrogens prefer beta, too? No. 8-PN is a selective estrogen receptor alpha promoter. “Surprisingly and in clear contrast to genistein [the soy], 8-PN is a much weaker” binder of beta than of alpha. So, that explains why hops is such a common ingredient in so-called breast enhancing supplements—that is, because it acts more like estrogen estrogen. Given the breast cancer concerns, use of such products should be discouraged, but just drinking beer could provide the exposure to the hops estrogen, which could help explain why beer may be more carcinogenic to the breast than some other forms of alcohol.


A phytoestrogen in beer? For more on the background of this issue, see The Most Potent Phytoestrogen Is in Beer.

Other videos on phytoestrogen include:

To learn more about dietary effects on testosterone, see:

What about “natural” hormones for menopause? See my video Plant-Based Bioidentical Hormones.

For more on the risks of alcohol in terms of breast cancer risk, see Breast Cancer and Alcohol: How Much Is Safe? and Breast Cancer Risk: Red Wine vs. White Wine.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Beer Phytoestrogens

Why do alcoholic men develop so-called man boobs and other feminine traits? We know estrogens produce feminization, and our liver clears estrogens from the body. As such, the original theory was that alcohol-induced liver damage led to the retention of excess estrogens. The problem was that when researchers measured estrogen levels, they weren’t elevated. What’s more, even those with cirrhosis of the liver appeared to clear estrogens from the body normally, and men’s testicles started shrinking even before serious liver disease developed.

So, alternative explanations were considered. 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”—perhaps 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 called genistein, present in a type of clover, and the same phytoestrogen found in soybeans.

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 1,000 cartons of soymilk a day or eat more than 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 that describe 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, back in 1951, we realized plant compounds could be estrogenic. Two German researchers realized that perhaps 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. In 1999, however, a potent phytoestrogen called 8-prenylnaringenin was discovered in hops, which I discuss in my video The Most Potent Phytoestrogen Is in Beer. In fact, it’s the most potent phytoestrogen found to date, fifty times more potent than the genistein in soy, “provid[ing] an obvious explanation for the menstrual disturbances in female hop workers in the past.” Today, we have machines to pick our hops, so our only exposure is likely via beer consumption, but the levels in beer were found to be so low that they shouldn’t cause any concern.

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. This study was conducted on mice, though. Thankfully, a study using human estrogen receptors found no such liver transformation, so all seemed fine…until 2005. “[T] he 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.

Indeed, up to a 90 percent conversion was achieved. Up to 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 10-fold increase the exposure concentration.” This can explain why you can detect 8-PN in the urine of beer-drinkers for days: 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? See my video What Are the Effects of the Hops Phytoestrogen in Beer? for the update.


Other videos on phytoestrogen include:

What about GMO soy? See GMO Soy and Breast Cancer.

For menstrual health videos, see:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Cancer-Causing Caramel Color

Caramel coloring may be the most widely consumed food coloring in the world.  Unfortunately, its manufacture can sometimes lead to the formation of a carcinogen called methylimidazole, which was identified as a cancer-causing chemical in 2007. For the purposes of its Proposition 65 labeling law, California set a daily limit at 29 micrograms a day. So, how much cancer might caramel-colored soft drinks be causing? We didn’t know…until now… My video Which has more Caramel Coloring Carcinogens: Coke or Pepsi? explores these questions and more.

Researchers tested 110 soft drink samples off store shelves in California and around the New York metropolitan area, including Connecticut and New Jersey. None of the carcinogen was found in Sprite, which is what you’d expect since Sprite isn’t caramel-colored brown. Among sodas that are, the highest levels were found in a Goya brand soda, while the lowest levels were in Coke products, which were about 20 times less than Pepsi products. Interestingly, California Pepsi was significantly less carcinogenic than New York Pepsi. “This supports the notion that [labeling laws like] Proposition 65…can incentivize manufacturers to reduce foodborne chemical risks…” To protect consumers around the rest of the country, federal regulations could be a valuable approach to reducing excess cancer risk—but how much cancer are we talking about?

Johns Hopkins researchers calculated the cancer burden, an estimate of the number of lifetime excess cancer cases associated with the consumption of the various beverages. So, at the average U.S. soda intake, with the average levels of carcinogens found, Pepsi may be causing thousands of cancer cases, especially non-California Pepsi products, which appear to be causing 20 times more cancer than Coke. Of course, there’s no need for any of them to have any these carcinogens at all “as caramel colorings serve only a cosmetic purpose [and] could be omitted from foods and beverages…” But we don’t have to wait for government regulation or corporate social responsibility; we can exercise personal responsibility and just stop drinking soda altogether.

Cutting out soda may reduce our risk of becoming obese and getting diabetes, getting fatty liver disease, suffering hip fractures, developing rheumatoid arthritis, developing chronic kidney disease, and maybe developing gout, as well.

In children, daily soda consumption may increase the odds of asthma five-fold and increase the risk of premature puberty in girls, raising the likelihood they start getting their periods before age 11 by as much as 47 percent.

If we look at the back of people’s eyes, we can measure the caliber of the arteries in their retina, and the narrower they are, the higher the risk of high blood pressure, diabetes, and heart disease. Researchers performed these kinds of measurements on thousands of 12-year-olds and asked them about their soda drinking habits. Their findings? Children who consume soft drinks daily have significantly narrower arteries. “The message to patients can no longer remain the simplistic mantra ‘eat less, exercise more.’” It matters what you eat. “[S]pecific dietary advice should be to significantly reduce the consumption of processed food and added sugar and to eat more whole foods.”


Prop 65 is lambasted by vested interests, but, as I mentioned, it may push manufacturers to make their products less carcinogenic. Other Prop 65 videos include:

For more background on caramel coloring, see my video Is Caramel Color Carcinogenic?.

There are other soda additives that are potentially toxic, too. See my three-part series on phosphates:

Other coloring agents are less than healthy. For more on this, see Artificial Food Colors and ADHD and Seeing Red No. 3: Coloring to Dye For.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: