The Growing Confusion About Eating Soy Foods
While it may still be a newcomer to American diets, the soybean is an old friend in China: 5,000 year-old records show that it was a staple in the Chinese diet even then. During the U.S. Civil War, soldiers brewed the beans as "coffee berries" when real java ran scarce. Its popularity continued to grow and as early as the 1940s, the U.S. was producing 78 million bushels of soybeans annually. Today, soybeans are the second largest U.S. cash crop, and are grown in at least 29 states.
Most recently, however, the revered soybean has started to draw controversy. Although soybean research has been ongoing for decades, the 1990s saw this little bean thrust into the spotlight as a "wonder food," a dietary answer to heart disease, high cholesterol and cancer. However, soy is getting new scrutiny from critics who say that it can have damaging health effects. It’s enough to make most health-conscious consumers pause and question if the miso soup and veggie burgers they eat are as beneficial as they thought.
In October 1999, the Food and Drug Administration (FDA) gave its stamp of approval to soy, recognizing the consumption of 25 grams of soy protein per day as having a role in lowering cholesterol and, thus, the risk of heart disease. Lowering cholesterol remains the most widely accepted benefit of soy, according to scientific studies.
Following FDA approval, a flood of new soy food products hit the market, ranging from fake meats to soy-protein pills and supplements. Tonya Martin of Eden Foods says FDA approval was both a blessing and a curse to the industry. "It harmed by allowing lower-quality products to be rushed to market," she says. "But it also helped to raise awareness and get people to think about eating soy. People are starting to focus on quality now."
The public latched onto soy claims before sufficient scientific research and data backed them up. In the Report on Consumer Attitudes About Nutrition, produced by the United Soybean Board, 39 percent of consumers stated that they relate soy with some health benefits. One-third of that group linked soy to reducing the risk of heart disease. More interestingly, 18 percent of consumers associated soy’s benefits with cancer prevention, and 14 percent attributed soy to reducing menopausal symptoms—claims that have never been scientifically confirmed.
Indeed, such claims have recently come under fire by critics who feel soy’s health benefits are largely part of a successful marketing campaign. The Soy Online Service, a group of private citizens based in New Zealand with the mission to uncover the truth about soy, proclaims, "The soy industry is one of the world’s most wealthy and powerful, and one that will steamroll anybody that dares suggest there may be problems with soy."
About four years ago, Eden Foods began receiving calls from consumers asking for answers to anti-soy reports. The company eventually posted responses on its website. Martin attributes most of the criticism about soy to processed, denatured soy foods, which she says have been stripped of most of their nutrients and contain a lower protein quality. Properly cooked, whole soybean foods are exceptionally healthy, she says.
Health Food or Health Hazard?
Many of the health claims for soy relate to compounds called phytoestrogens, which are weak, plant-based sources of estrogen. One type of phytoestrogen is isoflavone, found in a variety of legumes. The soybean is one of the richest sources of isoflavones, although soy foods carry varying levels depending on how they are processed. One study found that four ounces of soymilk contained 10 to 20 milligrams (mg) of isoflavone. Four ounces of tofu contained 38 mg, and the same amount of uncooked soybeans had 175 mg. Isoflavones are also extracted from soybeans and sold in pill form.
One of the most prevalent isoflavones in soy, genistein, has been reported to bind to estrogen receptors and carry estrogen-like properties. Early studies found that genistein may play a role in cancer prevention by interfering with cancer cells. However, according to a study published in 2001 in the Annuals of Pharmacotherapy, genistein was found to stimulate existing breast tumor growth and interfere with Tamoxifen, a popular breast cancer medication.
Margo Woods, a professor in the Department of Family Medicine and Community Health at Tufts University School of Medicine, says the research community started taking a second look at soy after studies were released that contradicted early findings touting the health benefits. One study found that women who were consuming soy had higher levels of abnormal breast fluid cells than those who weren’t consuming it. "This causes some people to rethink soy, even though some of the other studies were very positive," says Woods.
Soy expert Mark Messina acknowledges that many of his views about the food have changed since he and his wife Virginia published their book The Simple Soybean and Your Health, in 1994. One evolving area has to do with lowering cholesterol. Now, Messina says he is less impressed with soy’s ability to lower serum cholesterol levels, especially when compared to cholesterol-lowering drugs. "I still encourage soy intake for protection against heart disease," he says, adding that the biggest benefit may be the direct effects of isoflavones on coronary vessels. Messina does see promise in soy reducing the risk of osteoporosis, because soy protein has been shown to cause less calcium loss from bones than animal protein and because phytoestrogens may both inhibit bone breakdown and stimulate bone formation.
At the Fourth International Symposium on the Role of Soy in Preventing and Treating Chronic Disease, held last November, new research was presented on a two-year study on post-menopausal women that related soymilk to preventing bone loss in the lumbar spine. Soybean critics counter that soy may in fact lead to osteoporosis because soy contains phytic acid (phytates), which prevents the absorption of certain minerals, including zinc, calcium and magnesium. But Eden Foods" Martin responds that phytic acid is present in other foods, including beans and grains. She says phytate-containing foods are prepared by removing the hull, which lowers the phytate concentration.
Some researchers worry that consumers will take reported health claims about soy as endorsements to consume vast amounts before science has substantiated such beliefs. "When we start telling people to take large amounts of phytoestrogen pills, then I think we’re not on hard ground," says Woods.
The Future of Soy
There is more soy research underway than ever before, partly because of anti-soy backlash. While studies continue on soy and cancer, osteoporosis and heart disease, new areas of research include cognitive function, skin care and kidney disease. In the meantime, most researchers recognize soy as a safe, excellent source of plant-based protein and essential fatty acids. "The best data we have is that people have been eating it for thousands of years," says Woods. "Eat it in reasonable quantities and don’t see it as a medicine."
ANNE W. DiNARDO continues to enjoy soy in Cincinnati, OH.