Think soy is the ultimate health food? Not so fast. Too much may just be too much of a good thing.
By Paul Tullis
August 2009
When I was growing up in Chicago, my parents did what they could to enrich my urban experience by getting me out into nature from time to time. Twice a year, my family would head to nearby Rockford, Illinois, to spend some time with our friends the Funderburgs. The Funderburgs' four boys, my sisters, and I would construct forts in the hayloft in summer and go snowmobiling through the fields in winter. When I was old enough to wonder about such things, I asked Mr. Funderburg what it was that he grew on his farm. "Mostly soybeans," he told me.
I'd never heard of the things. I come from a long line of professional meatpackers, and in Chicago—even among laypeople—eating beef or pork for breakfast, lunch, and dinner is even more endemic to our municipal culture than devotion to the Cubs.
Since those carnivorous days in the 1970s, soy foods have gone from a niche product for the vegetarian-environmentalist crowd to a four-billion-dollar-a-year food industry. Soy is now on nearly every sushi bar menu (edamame) and is used as a vegetable oil, as a meat and dairy substitute, and as an inexpensive additive to increase the volume and improve the texture of many processed foods. The legume is so ubiquitous that it has found its way into everything from peanut butter to canned tuna. Many studies have shown the possible health benefits of eating soy, so most people consider it a "health food." After all, it's high in protein and has zero cholesterol—what could be wrong with that?
Plenty, some say. Recent research has shown that soy may contain dangerous levels of isoflavones, natural chemicals that are similar to human estrogen. Isoflavones can affect fertility in men and may increase the incidence of breast cancer in at-risk women. Because of these concerns, the Israeli Ministry of Health has had a warning in effect since 2005. According to reports, the ministry suggests that adults moderate their soy consumption, that infants be given soy formula only when breast milk or cow's milk is not an option, and that parents limit the amount of soy their children eat. Health officials in France and Great Britain are concerned, too. French food manufacturers have been asked to reduce the isoflavones in soy formula, and are required to put warning labels on soy foods. The British Dietetic Association has warned parents against using soy formula during the first six months of a baby's life.
Not surprisingly, the Soyfoods Association of North America doesn't necessarily agree with these concerns. Nancy Chapman, the group's executive director, says that the Israeli Ministry of Health's warning was largely based on research that used rats, whose hormonal makeup and reproductive system don't accurately predict what may happen in the human body.
"Every time a study comes out that the soy industry doesn't like, they respond in one of two ways: It's poorly designed, or it's old," says Kaayla T. Daniel, Ph.D., a nutritionist and author of The Whole Soy Story. "Israel had a committee of more than a dozen distinguished nutritionists, researchers, pediatricians, and toxicologists who looked at the body of evidence, and concluded there was a risk."
Daniel is one of an increasingly vocal group of nutritionists and scientists who are concerned about the possible risks of consuming too much soy. "The soy industry can never prove safety," she tells me. "They'll trot out studies showing a benefit, and act as if all the others indicating a risk are not a problem."
About a decade ago, Daniel says, some of her clients began complaining about digestive problems, thyroid problems, and allergies they hadn't had before. She says each of them had suddenly increased the amount of soy in his or her diet. It just so happens that soy's reputation as a healthful alternative to animal protein was gaining traction around this time. In 1999, the Food and Drug Administration began allowing companies to claim that foods with soy protein "may reduce the risk of heart disease." This claim was based on early research that showed that soy protein could lower "bad" LDL cholesterol levels.
Later studies were less conclusive—and the amount of soy protein consumed to reap the benefit would have to be the equivalent of 1.5 pounds of tofu or half a gallon of soy milk a day. As a result, in 2008 the American Heart Association recommended that the FDA rescind the health claim. Linda Van Horn, Ph.D., professor of preventive medicine at the Northwestern University Feinberg School of Medicine and chair of AHA's Nutrition Committee, says the quality and quantity of studies on soy and heart health have improved tremendously since the claim was first made. "When we looked at all the evidence, we didn't see enough to support the claim that soy is a blood-cholesterol-lowering agent," she says.
Muddying the waters further are scientific studies that have reached very different conclusions. Soy can reduce the risk of breast cancer (Journal of the National Cancer Institute, 2006); it has no effect (Cancer, 2007); it can actually increase the risk (Cancer Research, 2001); soy can help memory in postmenopausal women (Menopause, 2003); no, it can't (Journal of the American Medical Association, 2004).
What is clear today, according to the Harvard School of Public Health, is that when it comes to soy and health, "some of the claims...go far beyond the available evidence." The AHA still says that it's perfectly fine to eat soy as part of a varied diet, and Van Horn continues to recommend soy to some of her patients, and to eat it herself.
So what's the bottom line? If you're a woman who has been diagnosed with or has a family history of breast cancer, it's probably safest to avoid soy. Men hoping to father children should probably limit the amount of soy they eat, and parents would be advised to follow the Israeli guidelines in serving soy foods to their kids, especially infants and toddlers.
That's what our family is doing (even though we're done having kids, thank you very much). Because ironically—or perhaps not—my two young daughters (descendants of meatpackers, mind you) have never eaten meat. My wife and I had relied heavily on soy products early in the girls' lives, so I freaked out when I first learned of the health problems they might cause. We've since expanded our menus to include other vegetarian protein sources like lentils, black beans, and black-eyed peas. But there's still room for some soy. We just check ingredients to avoid the food products that it's sneaking into and buy organic whenever possible. As with most things in the health arena, moderation is key. Even Kaayla Daniel agrees. "Miso soup, tempeh, occasional tofu—the old-fashioned, whole soy products eaten modestly—are nourishing foods, and there's little risk to them," she says.
Let It Ferment
When it comes to soy and health, there isn't much consensus. But there is one thing that both the anti- and pro-soy camps seem to agree on: Fermented soy is good for you.
The fermentation process alters the chemical makeup of soy, which reduces the level of potentially harmful isoflavones (plant estrogens). Scientific studies have found that non-fermented soy foods (soybeans, soy powder) have as much as three times the isoflavones as the fermented stuff.
Fermented soy foods include soy sauce and miso, which is most commonly associated with miso soup. Vegetarians will recognize tempeh, a fermented soybean cake that is often used in place of meat.
More adventurous eaters might consider adding natto—somewhat stinky fermented soybeans—to their diets. One study suggests that an enzyme in natto might be effective in battling Alzheimer's disease. Researchers theorize that the enzyme may be able to break up the protein that forms the memory-altering deposits on the brain.
Source: http://www.bonappeti.../is_soy_healthy
Edited by Nané, 25 August 2009 - 11:36 AM.
