Publicity has made the bright green soybean a health hit growing on 72 million acres of US soil. But with fame, notoriety often follows. Now this $420 million industry of proteins, powders and meat and dairy substitutes is starting to generate its share of controversy–and forcing consumers to weigh all possible benefits and risks.
“Just imagine you could grow the perfect food,” wrote Dean Houghton in a recent article for The Furrow. “This ideal food would prevent, and perhaps reverse, some of the world’s most dreaded diseases.”
He’s referring to soy and his enthusiasm isn’t unusual. Nearly a century after Russian scientists first hypothesized that vegetable protein could reduce coronary heart disease, the soybean has hit the big time.
In 1995, the New England Journal of Medicine published a meta-analysis of 38 studies and concluded that soy is effective in lowering high cholesterol levels. Eating 47 grams of soy protein a day (about three tablespoons) lowered total cholesterol levels by 9.3 percent, low density lipoprotein (LDL) cholesterol by 12.9 percent and triglycerides by 10.5 percent.
According to the US Food and Drug Administration, eating 25 grams of soy protein a day can lower the risk of coronary heart disease. The official stamp of approval came last October when the FDA approved the use of health claims on soy labels. To qualify, these foods must contain 6.5 grams of soy protein per serving. They must be low in saturated fat, total fat and cholesterol. In return, companies can promote their product as a benefit to cardiovascular health.
You can bet consumers won’t overlook the added possibility of cancer prevention when they walk down the grocery aisle. One gram of soybeans contains about one milligram of isoflavones, or phytoestrogens (phyto meaning plant) believed to have anti-carcinogenic properties. In particular, the genistein and daidzein isoflavones in soy foods affect hormone metabolism and estrogen activity. They have the capacity to bind with estrogen receptors, thus blocking estrogen uptake by cells and aiding hormone-related conditions, including certain cancers.
To a continent struggling against degenerative disease, Japan’s lower rates of breast and prostate cancer–attributed to higher consumption of soy products–are compelling. In this vein, researchers reported in the Lancet that of the 288 women studied, those who excreted the least amounts of isoflavones–indicating a lower intake of soy–were four times as likely to have breast cancer.
Offering still more bang for the buck, soy is proven to benefit osteoporosis. Animal protein leeches calcium from the bones to protect against the protein’s acidic nature. In contrast, recent studies suggest that alkaline soy isoflavones both inhibit the breakdown of bones and stimulate bone health. Phytoestrogens have also been shown to provide some relief to women with menopausal symptoms.
Oh Soy Good?
With its many proven health benefits, it’s no wonder soy sales have soared. However, a few scientists worry that with products and supplements so popular, some North Americans may inadvertently consume too many soy isoflavones. The hormonal effects, they fear, may not always be a good thing, especially for postmenopausal women and/or those with estrogen-dependent breast cancer.
One problem lies in the common perception that soy protein is the same as soy isoflavones. The FDA distinguishes between them by permitting health claims for soy protein, not for isoflavones, which are frequently isolated, added to products or sold in supplement form. One has proven beneficial; the other has not undergone the same study to determine safety levels.
A January article in The New York Times unexpectedly challenged the soy status quo. “Not one of the 18 scientists interviewed for this column was willing to say that taking isoflavones was risk free,” wrote reporter Marian Burros.
According to Dr Margo Woods, an associated professor at Tufts University School of Medicine, it’s wiser to talk about soy and soy foods than isoflavones or phytoestrogens.
“A whole food behaves very differently in the body than when you take one compound. We are looking into components, but we haven’t been studying in the area long enough,” she said.
Two soy opponents, Sally Fallon and Dr Mary Enig, further question the act of taking soy out of its traditional dietary context. As with all grains, the unadulterated soybean contains enzyme inhibitors and phytic acid, a substance that can block the uptake of essential minerals. However, the first soy foods–such as tempeh, natto, miso and soy sauce–were slowly fermented to help deactiviate anti-nutrients and aid digestion. They were served also in small amounts complemented by a mineral-rich fish broth.
Using contemporary processing methods, some (but not all) anti-nutrients are removed. It has also been argued that the texturized, treated end product is somehow different from nature’s original soybean.
In the end, more research is needed to determine both the health effects of various soy-derived components and soy’s interaction with other foods. As for the everyday diet, moderation and variety seems to be two key ways of avoiding health problems and getting the most from soy favorites.