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Beer contains 8-prenylnaringenin, one of the most potent plant-derived estrogens ever discovered. But don’t worry about adverse effects.

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It seems that just about everything we eat or drink has been the subject of a cancer scare. Acrylamide in toast, heterocyclic amines in steak, nitrites in hot dogs, methylimidazole in colas, casein in milk and aflatoxins in peanuts are all reputed carcinogens.

It’s enough to drive you to drink. But there are issues here as well.

Beer contains 8-prenylnaringenin, one of the most potent plant-derived estrogens ever discovered. Estrogenicity can be determined by measuring how strongly a suspect compound binds to estrogen receptors in the uterus of a rat, and 8-prenylnaringenin binds very strongly. This is why hops are often found in dietary supplements that are claimed to enhance breast size.

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The theory is that the female hormone estrogen is responsible for the so-called secondary sex characteristics, namely the features that first appear in puberty and distinguish men from women. Breast growth is an obvious example. Transgender procedures that require feminization always include the administration of estrogen for breast development. But in women, there is no evidence that breast size is determined by circulating estrogen and no reputable studies have ever shown that breast-enlargement supplements work.

However, this does not mean that phytoestrogens in hops have no physiological activity. The flowers of the hop plant, Humulus lupulus, have been used since about the ninth century to give beer its characteristic bitter flavour and to keep it from spoiling. While hops do not interfere with the activity of brewer’s yeast, they can eliminate other undesirable microbes and help preserve the beer.

Until the advent of picking machines, hops were gathered by hand, often by women. Historical anecdotes claim that the menstrual cycles of these women was altered by the handling of hops. There are also stories about beer-drinking men not being able to rise to the occasion with the ladies when required because they were afflicted by “Brewer’s Droop.” As if that weren’t enough, there are allegations that drinking beer results in “man boobs.” Neither the menstrual problems nor the effects on men have been confirmed by studies, so they remain anecdotal. Beer can add a lot of calories to the diet, resulting in the classic beer belly and in excess adipose tissue around the chest, but this is not a hormonal effect. Also it is known that excessive alcohol consumption can lead to erectile dysfunction, an effect that has nothing to do with hops.

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As far as the estrogenic 8-prenylnaringenin found in hops is concerned, virtually none is detected in beer. But there still is a niggling issue. Our gut contains trillions of bacteria, part of the human “microbiome,” that are capable of carrying out a variety of chemical transformations. One of these is the conversion of another compound found in beer, isoxanthohumol, into the estrogenic 8-prenylnaringenin. So while this compound may not be present in beer, it can form in the body after beer is consumed, meaning that we are not home-free when it comes do dismissing any physiological effect that beer may have. In any case, such an effect is likely to be trivial. But this is not the case for hop flowers.

When menopausal women were given about half a teaspoon a day of dried hop flowers in a placebo-controlled study, hot flashes and other menopausal symptoms almost disappeared after three months. This would seem to be indicative of an estrogenic effect, one that raises an issue. Estrogen supplements have a history of use against menopausal symptoms and it used to be quite routine for doctors to prescribe these to woman as soon as they reached menopause. But this practice was mostly discontinued when studies revealed that such supplements increased the risk of breast cancer.

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Given that the hops supplement reduces menopausal symptoms in a fashion similar to prescription estrogens like Premarin, so-called because it is extracted from the urine of pregnant mares, might it not also increase the risk of breast cancer? Research has shown that 8-prenylnaringenin binds to the same estrogen receptor, termed the alpha-receptor, as do the prescription estrogens, so the possibility that hops or hop extracts can increase the risk of breast cancer cannot be discounted. This may well be a real concern with the large doses of hops used for menopausal symptoms, or hop extracts found in breast enlargement pills, but is unlikely to be the case when it comes to the much smaller amounts of 8-prenylnaringenin that show up in the blood after consuming beer.

In any case, it is unrealistic to single out beer as a source of phytoestrogens. Dozens of foods including flaxseeds, rice bran, wheat germ, almonds, walnuts, lentils and soy contain such compounds. In Japan, far fewer women report suffering from hot flashes, and this is thought to be due to significant soy consumption. There is no association with breast cancer, possibly because genistein, the phytoestrogen in soy, binds to “beta-estrogen receptors,” which reduce cell proliferation unlike “alpha receptors,” which increase it. But stimulation of either type of receptor seems to reduce menopausal symptoms. As always, there is a dose effect.

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In very high doses, genistein can have negative effects. We first learned about this compound in 1951, when Australian researchers linked infertility in sheep to its presence in clover the animals were eating. Genistein was actually the first hormone-like substance discovered in plants. The observation of infertility in sheep has been interpreted by some as a demonstration of the dangers of soy and admonitions to stay away from this legume. But a human would have to eat about 300 kilograms of tofu a day to approach the intake that caused the problem in the sheep!

Bottom line is that phytoestrogens that are found in a balanced diet are not an issue. If you want to worry about something in beer, though, worry about the alcohol. That is a well-established carcinogen.

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Joe Schwarcz is director of McGill University’s Office for Science & Society ( He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.

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