Study Led by Colorado State Indicates Soy Consumption Could Help Prevent Prostate Cancer and Male Pattern Baldness

A team of scientists has discovered that a little-known molecule created in the intestine when soy is digested is a natural and powerful blocker of a potent male hormone involved in prostate cancer and male pattern baldness. In fact, according to the Colorado State University led study, the molecule, equol, completely stops in its tracks the male hormone dihydrotestosterone, or DHT, which normally stimulates prostate growth and causes male pattern baldness. The study, conducted at Colorado State, Brigham Young University and Cincinnati Children’s Hospital Medical Center, appears in the April edition of the journal Biology of Reproduction.

"Directly binding and inactivating DHT without influencing testosterone gives equol the ability to reduce many of the harmful effects of androgens without affecting the beneficial ones," said Robert J. Handa, senior author of the study, professor and associate head of graduate studies of the Department of Biomedical Sciences at Colorado State’s College of Veterinary Medicine.

"To date, no other compound has been shown to directly bind DHT; rather, all other drugs target the receptor for DHT or the enzymes that are involved in the synthesis of DHT," added Trent Lund, lead author of the study and assistant professor in the biomedical sciences department at Colorado State.

In recent years, the pharmaceutical industry has developed drugs that inhibit a certain enzyme that converts testosterone to DHT. Unfortunately, these drugs have side effects. Equol, on the other hand, does not prevent DHT from being made but prevents it from functioning. It puts "handcuffs" on DHT, preventing it from binding to the androgen receptor and thereby preventing the prostate from growing. This may be particularly important for men who have been diagnosed with either an enlarged prostate (benign prostatic hyperplasia), or cancer of the prostate.

"This molecule is remarkable," Kenneth Setchell, director of Clinical Mass Spectrometry at Cincinnati Children’s Hospital Medical Center, who first identified equol in humans 20 years ago.  "These findings are of immense clinical importance because blocking the action of the potent androgen (male hormone) DHT has been one of the holy grails of the pharmaceutical industry as a strategy for treating prostate cancer and other related diseases. This natural metabolite made from soy isoflavones, which are found in high amounts in soybeans, does this very effectively."

Two experiments demonstrated that injections of equol into male rats reduced the size of the prostate. In one study, the testes of male rats were removed, thereby eliminating all DHT production. When investigators injected DHT into rats, their prostates grew. When they injected rats with both equol and DHT, the equol prevented the DHT from functioning as it normally would – as a stimulator of prostate growth.  

In other words, equol did not change hormone levels but completely blocked the effects of DHT in rats. This could explain why men in Japan, who eat more soy than American men, rarely have prostate cancer, according to Setchell.

Several human studies have demonstrated the advantages of eating soy in reducing the risk of prostate cancer; however, only about 30 percent of all people in America have the correct bacteria in their intestines to convert soy to equol.

"The novelty of equol is that it both inhibits androgen hormone and influences estrogen hormone action," said Edwin Lephart, professor of physiology and developmental biology and director of the Neuroscience Center at Brigham Young University. "We do not know of any other molecule that possesses these important biochemical properties."

So far, research has established the relevance of DHT in the growth of male reproductive organs and, given the importance of DHT in the skin; it is possible that equol may offer a means of controlling hair loss and promoting healthy skin.

The researchers have initiated further studies of equol to assess its potential as a treatment for a variety of other androgen-mediated conditions. The team has filed patent applications on equol and hopes to commercialize the technology.