Should Men Worry?

If you’re like me, you’ve probably heard the rumors about soy. That it can make men infertile or that it has a feminizing effect. You might be thinking twice about the amount of soy you’re eating, or possibly wondering whether you should drink soymilk at all!

Well, you can stop worrying. While the soy debate rages on, the important facts have been verified. The short story is, no, soy doesn’t have any kind of feminizing effect on men – although experts recommend eating whole soy foods, such as tofu and soymilk, rather than extracts and isolated proteins. The Asian countries where whole soyfoods are consumed regularly don’t seem to be having population problems!

Here’s one study result cited by Clare M. Hasler, Ph. D.:

In a recent study looking at soy’s affect on reproductive health in healthy males, men given 40 mg of soy isoflavones daily for 2 months (there are 20 mg of isoflavones in 1 cup of soy milk; 38 mg in 1/2 cup of tofu), there were no effects on serum sex hormones, testicular volume, or semen quality. This was deemed the first study to examine the effects of a phytoestrogen supplement on reproductive health in males. (Mitchell et al., Clinical Science 100(6):613-618, 2001 June)

We’ll move on to a Q&A from health expert Virginia Messina:

Q: As an almost vegan, I consume a lot of soy. As a 21-year-old guy, I was wondering if the estrogen in soy that is so good for women might be doing weird abnormal stuff to me like reducing my testosterone levels. If so, how bad is this? Should I be consuming less soymilk and tofu?

A: Soybeans contain plant forms of estrogen called phytoestrogens (the chemical name is isoflavones). Phytoestrogens have very weak estrogen-like activity but can also act like antiestrogens, reducing the effects of naturally-produced estrogen. This is one reason that soy might possibly be protective against the development of some types of breast cancer which are stimulated by estrogen.

There is no evidence that men who eat moderate amounts of soy experience any feminizing effects, which is what I am guessing you are concerned about. Certainly we don’t see these effects in cultures where daily consumption of soy is common.

There is some evidence that vegetarian men have somewhat lower blood testosterone levels than omnivore men. There are several possible explanations for this. Soy consumption could certainly be one of them but the evidence for this is not very clear. The higher fiber intake of vegetarians could also affect testosterone levels. Also dietary fat and obesity increase testosterone levels and vegetarians tend to eat less fat and be slimmer.

But before you bolt for dinner at the nearest steakhouse, let’s put this into perspective. There is no evidence that vegetarian men have testosterone levels that are too low. There is a range of what is normal and as long as you are in that range, there is no advantage to being at the higher end of the range. In fact, being at the lower end of the normal range could have benefits. For example, lower testosterone levels are associated with reduced risk for prostate cancer in some studies. And, not surprisingly, there is evidence that consuming soy reduces risk for prostate cancer. This compares to the situation in women. Evidence suggests that vegetarian women have lower estrogen levels-perhaps for the same reasons noted above for testosterone. And this might help to protect against breast cancer.

Because the average American is a meat-eater, we have a tendency to base our ideas of what is normal or optimal based on what occurs in meat-eaters. Of course, we know that for many things this is not true. For example, “normal” cholesterol levels-the levels typically seen in meat eaters-are too high for good health. The situation for testosterone may be similar. Judging these levels based on those that occur in people eating an unhealthy diet doesn’t make sense.

Now we know that soy’s phytoestrogen content isn’t going to be a problem – it may even be healthy. According to an FDA scientific review, soy does not interfere with childhood growth, does not cause pancreatic or breast cancer, does not significantly interfere with mineral absorption as long as dietary consumption is adequate, does not induce early puberty, and does not interfere with fertility. There is even some evidence that eating soyfoods can enhance fertility in men. One of the isoflavones in soy may be used to treat male sterility because of its positive hormonal effect on normal sperm production.

Now What?

So what does this mean for you? Should men worry? No! It means don’t worry about consuming soyfoods. Foods like soymilk, tofu, tempeh, miso, soy nuts, edamame and soy sauce aren’t going to be a problem. Soymilk made from soaked, grounded whole soybeans rather than powders or proteins is the best. And there’s no better way to control what goes into the soymilk than by making your own! You can even use a combination of soybeans and other nuts or grains to make it taste the way you want.