I recently came across an article on WebMD that suggests soy consumption may help prevent male pattern baldness and prostate cancer: http://men.webmd.com/news/20040330/soy-prevent-prostate-cancer-male-baldness However, there is no lack of controversy surrounding soy. For every source or study that supports soy consumption for its perceived benefits, there seems to be another that cites adverse effects. For example, there are those who believe that soy consumption leads to gynecomastia (breast enlargement in men), reduced testosterone and libido, as well as an unfavorable effect on lean body mass. Because I am only a layman, I found myself out of my depth amid this controversy. Therefore, I contacted Dr. Joe Schwarcz, Director of McGill Universityâs Office for Science and Society, which is dedicated to demystifying science for the public, the media and students. Dr. Schwarcz was kind enough to e-mail me an excerpt from his book, An Apple a Day, which touches on soy. Here is that excerpt: Soy Protein and Soy Isoflavones I never thought I would get excited about tofu. Frankly, the taste doesnât thrill me. But I am intrigued by some of the scientific studies that have linked eating soy products to protection from disease. Japanese women, for example, have one quarter the breast cancer rate of North Americans. And Japanese women eat a lot of soy products. Of course this does not necessarily mean that soy consumption has anything to do with breast cancer; after all, there is a very strong association between the disease and the wearing of skirts. But of course nobody thinks that the wearing of skirts causes breast cancer. However, it may well be that the soy connection is more than just a chance association. Before exploring the possible benefits of soy, though, letâs remember that breast cancer is a complex disease with many possible contributing factors. It is age-related, has a genetic component and is also linked to excessive alcohol consumption. There may be a connection to high levels of certain fat-soluble pesticides and the types of fat in the diet may also play a role. Our soy saga really starts back in the 1940s when Australian farmers noticed that sheep grazing on a certain type of clover failed to reproduce normally. Vetenarians found that the animalsâ urine contained high levels of equol, a compound previously found in the urine of pregnant horses. As it turned out, bacteria in the sheep's intestine were capable of converting a naturally occurring compound in clover to equol. And equol was known to have biological activity similar to estrogen! It was no great surprise that an estrogen-like substance should interfere with fertility; after all, estrogen was known to play an important role in human reproduction. Scientists then began to wonder if other plants might also produce compounds with estrogenic activity. Enter the soybean. This Asian staple turned out to be rich in phytoestrogens (plant-derives estrogens), known as âisoflavones.â Genistein and daidzen, in particular, were of interest because they were partially excreted in the urine and could be correlated with the amount of soy in the diet. The discovery of phytoestrogens raised eyebrows because scientists already suspected that estrogen and breast cancer were somehow connected. Women exposed to more estrogen over a lifetime were known to have a higher risk of contracting the disease. This includes women who come into puberty early, reach menopause late or have few or no children. In other words, it seems that any factor that lowers the total number of menstrual cycles over a lifetime lowers the risk. Now we get back to our Japanese women. They have longer menstrual cycles, averaging 32 days compared with the North American 29 days. This could mean thirty to forty fewer periods in a lifetime. They also have up to a thousand times more phytoestrogens in the urine than North American women. But the soybean plot really thickens when we note that Japanese consume 30 times more soy products than we do, and that Japanese who migrate to North America and take up the North American diet and lifestyle show cancer rates comparable to other Americans. We can even postulate a possible mechanism for the isoflavone-breast cancer connection. Some cells in breast tissue are known as estrogen-responsive, meaning that they contain certain proteins (estrogen receptors) to which estrogen can bind, very much in the fashion of a key fitting into a lock. This binding unleashes a sequence of events in the nucleus of the cell which eventually leads to the manufacture of certain proteins that cause cell proliferation. It is such abnormal cell multiplication that leads to cancer. Isoflavones, it seems, are actually "weak estrogens." They fit into estrogen receptors but do not stimulate much cellular activity. At the same time, they prevent estrogen from binding with the receptor. It is as if the wrong key had been inserted into the lock. The key cannot be turned, but it effectively prevents another key from being inserted. So much for associations and theory. What practical evidence can we muster to show that soy may actually prevent breast cancer? A number of animal studies have demonstrated that the consumption of soy or isolated isoflavones reduces tumor development. Harvard researchers found that rats fed isoflavones for two weeks before being injected with breast cancer or prostate cancer cells developed far fewer tumors than control rats. Animals that drank tea in addition to the isoflavones did even better. Human data is less direct, but some does exist. Dr. David Jenkins of the University of Toronto examined urine from volunteers on a low fat diet that included 33 grams of soy protein a day. The diet resulted in reduced hormonal activity in the urine as measured by the effect on human breast cancer cell lines. Jenkins suggests this corresponds to a slight protective effect against breast cancer. Researchers have also compared groups of breast cancer patients with matched controls and noted a decreased risk of up to 50% in premenopausal women who consumed soy daily. A classic study in Singapore showed that breast cancer rates correlated inversely with the amount of soy protein eaten on a regular basis. More than twenty studies of Asian women have shown that even 1 cup of soy milk or half a cup of tofu a day is associated with reduced cancer risk. In addition, some studies have found that menopausal women who start eating 20 grams of soy protein powder daily, (roughly equivalent to a soy burger, a cup of soy milk or a serving of tofu) show a reduction in the severity of menopausal symptoms. An added benefit is increased bone density in the spine. As far as premenopausal women go, the same kind of diet increases the length of their menstrual cycles by 2.5 days, while the isoflavone content of their urine also rises dramatically. It is certainly apparent that soy has estrogen-like activity! Genistein, the main isoflavone, may have yet another effect. It decreases the growth rate of blood vessels that nourish tumors. This inhibition of "angiogenesis" may turn out to be an important anti-cancer effect. It may even explain why men who have high levels of genistein in the urine seem to be protected from prostate cancer. Although the isoflavones appear to be the most interesting anti-cancer compounds in soybeans, there are others. Folic acid, for one, has been shown to prevent mutations in DNA. There are, however, some inconsistencies in the soy saga. A study of Japanese women showed that women with breast cancer had consumed no less soy than a control group unaffected by the disease. Chinese women, who eat only about a third of the soy based foods that the Japanese eat have the same low rate of breast cancer. Of course it is possible that a certain amount of soy is protective but eating more carries no further benefit, and may even present a risk. In the test tube, at very low concentrations, genistein enhances human breast cancer cell proliferation while at higher concentrations it inhibits it. The timing of soy consumption may also be important. Female rats, for example, are protected against carcinogen induced breast cancer if soy is given before puberty, but not if given later in life. In humans, isoflavones may act differently after menopause when natural estrogen levels are low, than earlier in life when copious amounts of estrogen are produced. Epidemiological studies of Asians do indeed show that it is soy intake early in life that is protective. Later on, at least in theory, when there is less competing natural estrogen, soy may have a different effect. Continued on next post.