By Sally Squires
Washington Post Staff Writer
Tuesday, May 4, 2004
Yes, it's true that your wife, girlfriend or significant other has been eating a lot of soy lately, mainly to boost her female hormones. That doesn't mean it's bad for you, fella. Instead of pushing aside that soy milk, go ahead and pour some on your morning cereal. Dig into the soy burgers at the office cafeteria and the tofu that appears in your takeout stir-fry.
It turns out that soy, at least in the doses most people will consume it in food, may be good for guys, too. A growing number of studies suggest that soy has plenty of health benefits for men -- from lowering cholesterol levels to protecting against prostate cancer -- and few downsides.
"Real men should eat soy," said Kenneth Setchell, professor of pediatrics at the Cincinnati Children's Medical Center, who has studied soy for 30 years. "Generally, men are put off by soy. It tends to be sort of a woman's thing. That's a great pity, because the evidence that soy protects against prostate cancer is quite strong."
While there have been worries that men who consume large quantities of low-carb soy bread, soy cereal or other soy-filled foods may get a little too in touch with their feminine sides, research findings have generally not borne out those fears.
"Soy is a very healthy food," said physician James Anderson, who has studied soy for 15 years at the University of Kentucky in Lexington and is convinced enough of its benefits to eat about a dozen servings of soy per week. "It's very safe."
Most concerns about soy have centered around the fact that it is a rich source of isoflavones, substances that mimic the effects of the female hormone estrogen. To determine what these plant-based chemicals might do, Steven Zeisel and his colleagues at the University of North Carolina at Chapel Hill fed megadoses of soy to men as part of a recent National Cancer Institute study.
Nipple discharge, breast enlargement and slight decreases in testosterone occurred with the megadoses. But "we still couldn't find anything that was serious, and we went up to doses that are probably 30 times what you could get from normal foods," Zeisel said. "I don't think that there are a lot of estrogenic worries. Your testicles will not shrink and you won't have massive breast enlargement" from eating soy.
And if you stick with foods rich in soy as opposed to supplements, researchers say, there's no evidence of harm, unless you happen to be among the one in every 1,000 people who are allergic to soy. "It's quite difficult to overconsume soy, to be honest," said Setchell.
Not only is soy a rich source of high-quality protein, but it also contains complex carbohydrates that don't raise blood sugar as high as more processed carbohydrates. It has fiber, folic acid (a key B vitamin), healthy fat and antioxidants that help protect against cancer.
There's also evidence that soy acts as a probiotic in some people, promoting growth of healthy bacteria in the gastrointestinal tract that in turn produce health-promoting substances. While it's possible these days to eat soy at every meal and snack, it only takes a small amount of soy to produce health benefits. Less than a handful of soy nuts, about a fifth of a cup, provides 12 grams of protein, said Anderson, who keeps a stash near his desk for snacks. "If you can eat a third of a cup a day, that would give good protective levels in terms of heart disease."
Will such soy-filled products as low-carb bread, soy cereal, soy crackers and cookies have the same benefits as traditional soy sources?
"My feeling is that soy milk and tofu have the best test of time," said David Jenkins, professor and chairman of nutrition and metabolism at the University of Toronto and St. Michael's Hospital in Toronto. The soy isolates found in meatless burgers and hot dogs "have also been shown to be very effective," Jenkins said. By contrast, soy sauce has only minimal levels of active soy ingredients and comes with massive amounts of sodium.
Just resist any urge to eat raw soy. Uncooked soybeans contain a substance that inhibits trypsin, a key enzyme required for protein digestion. "Horses who eat raw soybeans die," said Zeisel. While raw soybeans may not be as deadly for humans as they are for horses, Zeisel said it's not worth the risk: "Don't ever eat soybeans raw."
Here's how cooked soy stacks up in health benefits:
Bone health Studies suggest that soy helps preserve bone and may help build it in some people. While nearly all the research has been done in women, who suffer more extreme bone loss with age than do men, researchers say there's no reason to suggest that soy may not also help protect older men from osteoporosis.
Blood pressure Soy appears to lower blood pressure slightly. It also seems to lower blood pressure by "improving elasticity of blood vessels," Setchell said.
Cholesterol Since 1999, foods containing 6.25 grams of soy protein per serving can be promoted for their ability to lower blood cholesterol when combined with a diet low in saturated fat and cholesterol. About 25 grams of soy protein daily helps lower the most damaging form of blood cholesterol -- low-density lipoprotein (LDL) -- by up to about10 percent and total cholesterol by up to 7 percent, according to Anderson. There's also evidence that blood triglyceride levels rise less after a meal containing soy and that eating a diet rich in soy may help reduce the metabolic syndrome -- a constellation of symptoms that include elevated cholesterol, blood pressure and extra fat at the waistline.
Colon cancer A few studies suggest that soy may help protect against colon cancer, but the evidence is still emerging.
Diabetes Soy contains healthy carbohydrates with a low glycemic index, meaning they are less likely than more-processed carbs to raise blood sugar levels. New research also suggests that eating soy food appears to help protect the kidneys of those with diabetes, especially those with type 1.
Studies in Europe and at the University of Illinois also suggest that soy helps reduce protein in the urine of people with diabetes, which can help reduce kidney damage, a common complication of diabetes.
Hair loss Soy helps boost production in the intestines of equol, a substance that binds to dihydrotestosterone, the chief culprit in causing hair follicles to die. Although still in early investigation, Setchell and other researchers theorize that boosting equol could help protect against baldness.
Muscles As a protein source, soy ranks at the top of the list. But no need to take massive doses of soy protein supplements or powder to build more muscle. Eating a soy burger, a handful of soy nuts or a soy smoothie after a weight training session is plenty to help repair muscle, according to Jeff Potteiger, an exercise physiologist at Miami University in Ohio.
Prostate In Asian countries, where soy consumption is high, incidence of prostate cancer is similar to that in Western countries, but the disease is much less likely to kill. Studies of Seventh-Day Adventists, who eat no meat, have found that drinking one glass per day of soy milk appears to lower prostate cancer risk by 30 percent; two glasses per day may lower risk by up to 70 percent. At the University of North Carolina, researchers found men with elevated blood levels of prostate-specific antigens (PSA) who took megadoses of soy showed a significant slowing in rise of the PSA.
Waistline Soy foods are lower in calories, total fat and saturated fat than comparable meat products, and they have zero cholesterol -- all benefits that can help protect against obesity. There's also some evidence that soy may help reduce buildup of dangerous visceral abdominal body fat, according to Anderson.
For that reason, some soy researchers, including Anderson, Setchell, Jenkins and Zeisel, say they're putting their findings into practice by pouring soy milk on their cereal, snacking on soy bars and eating a soyburger instead of a hamburger. Example: A beef burger has about 190 calories, 11 grams of fat, four grams of saturated fat, zero carbs and no fiber, while a soyburger contains 50 fewer calories, a third of the fat, 10 grams of carbohydrates, three grams of fiber and zero saturated fat and cholesterol.