That soy latte with extra foam and nutmeg sprinkles probably isn't helping you to look manly. But it also isn't helping you to be manly. Researchers at the Harvard School of Public Health published a study last week in the journal Human Reproduction indicating that high levels of soy consumption are associated with low sperm counts in men. So if you're worried about your swimmers, maybe you should check your diet.
The study was designed to examine the relationship between semen quality and consumption of phytoestrogens. Phytoestrogens are non-steroidal compounds found in plants; when eaten they can imitate the effects of estrogen. Researchers surveyed 99 men at a fertility clinic. They were particularly interested in evidence of a history of eating a category of phytoestrogens called isoflavones (daidzein, genistein and glycitein). These substances appear in soy-based foods, so researchers asked the men about their consumption of tofu or tofu-based products, soy milk, tempeh, and other soy products such as drinks, powders and energy bars. Based on the survey, men were divided into four groups, divided by the amount of soy and isoflavones they consumed. Researchers adjusted the data to account for other factors such as age, alcohol consumption, and tobacco use. The result? The men in the highest soy intake group had 41 million fewer sperm per milliliter than men who ate no soy. A normal sperm count is 80 to 120 million sperm per milliliter—so those 41 million are a significant effect.
Clearly, researchers are very interested in just how much soy is too much—and initial data suggests that it doesn't take a bucket of tofu to cause problems. "Men in the highest intake group had a mean soy food intake of half a serving per day," said Dr Jorge Chavarro, a research fellow in nutrition at the Harvard School of Public Health and a lead author on the study. "In terms of their isoflavone content, that is comparable to having one cup of soy milk or one serving of tofu, tempeh, or soy burgers every other day." Of course, soy addicts might consume substantially more soy than a mere half-serving each day. As Dr. Chavarro pointed out, "It is important to highlight that the figure of half a serving a day is the average intake for men in the highest intake group. Some men in this group had intakes of soy foods as high as nearly four servings per day."
Why exactly soy has this effect on sperm counts will require further research, but Dr. Chavarro theorizes that the phytoestrogens may interfere with hormonal signals that govern sperm production. A secondary finding in the study supports this theory—a whopping 72 percent of the men in the high-intake category were overweight or obese. Higher body fat is associated with increased estrogen production in men. The phytoestrogens from the soy coupled with the estrogen from their own body fat leaves overweight and obese men particularly vulnerable to low sperm counts.
Getting Your Boys Back (or, Start Your Own Sperm Farm)
First, don't panic—low sperm counts won't hurt your sexual performance or actual enjoyment of the dirty deed (an orgasm is still an orgasm). But if you want to re-grow your team—say, if you plan to father children anytime soon, or if it just bothers you not to have the thickest sperm count on the block—the Harvard study suggests the obvious solution of monitoring your soy intake. To keep you in the game, here are a few more suggestions for keeping your sperm count bigger, better, and uncut:
- Clean up your act. Smoking and excessive alcohol consumption both lower sperm counts. Alcohol in particular causes your liver to produce estrogen. Over-exertion will lower sperm counts as well. So those late nights at the club, dancing like crazy, smoking, and drinking—yeah, that's killing your tadpoles. Stay in, drink tea, chew gum, and get a good night's sleep. You'll have more energy and be better in bed tomorrow, and the little baby sperms will thank you.
- Loosen up and chill out. Hot testicles are sad testicles. Your sperm can't survive in a heated environment. That's why your testicles hang down below your body—to stay cool. So those cute underwear that you like so much—you know the ones, that pull your testicles tightly up against your body in a sexy package? Well, those are a sperm slaughterhouse. The sauna and the hot tub aren't helping either. To grow more sperm, try to keep things cool down there. Wear loose underwear (think boxers); stay out of heated environments; and try not to sit for long periods of time. For the same reason a chicken sits on an egg—to keep it warm—you should try not to hatch your testicles.
- Keep a lid on it. OK, this is a tough one: Frequent ejaculation decreases semen density. You'll just have less sperm in your semen if you are expelling semen very often. So if you feel you really need a high sperm count for some special occasion—say, your lesbian best friend has requested you hand over a plastic cup of your semen to help her make a baby—avoid ejaculating for about three days beforehand. You'll produce more and denser semen when you really need it.
- Stretch your limits. Excess body fat leads to increased estrogen production, and thus fewer sperm. Likewise, a paunchy stomach can smother your testicles when you're seated, making them heat up to a dangerous degree. So you really need to shed the extra pounds and give your boys some room to breathe. But watch how you go about it—excessive cycling, for example, is bad for your testicles. Why not kill two birds with one stone? Yoga is a great, testicle-friendly way to exercise, and it lowers stress hormones, which are also detrimental to sperm production.
- Rise and shine. Some studies have found that sperm levels are highest in the morning. So if you need a high sperm count, set your alarm, get up early, and get to it right away.