Soy is ubiquitous, from milk bottles and packets of tofu to energy bars, nuts, even burgers. From 2000 to 2007 alone, companies introduced more than 2,700 new foods with soy as an ingredient, helping soy food sales grow from about $2.6 billion to more than $4 billion during that time period, according to the Soyfoods Association of North America. And let’s not discount the hundreds of soy supplements crowding drugstore and health food store shelves, promising everything from bigger muscles to bone health to improved cholesterol levels, to name but a few benefits.
But along with this flurry of favoritism for soy (driven largely by FDA approval of the stated claim between soy protein and heart disease reduction in 1999) have come a couple of concerns about the subtropical plant and its derivatives. A study published in Human Reproduction in 2008 linked soy consumption to lower sperm counts. And animal studies in Taiwan have suggested that consuming large amounts of isoflavones in soy could disrupt fertility in women and the normal development of children. And what constitutes a large amount of soy? According to the National Institute of Environmental Health Science, 25 grams or more per day.
Now come a slew of new studies that add to the confusion. In 2009, researchers from the University of Massachusetts Amherst discovered how foods rich in soy bioactive compounds may reduce the risk of diabetes and heart disease. Another 2009 study found that women with breast cancer who ate more soy food were less likely to see the cancer return. And in 2010, a Molecular Nutrition and Food Research report showed how soy protein reduces inflammation and the accumulation of fat – leading to the possibility of farmers growing soybeans that have a slimming effect. University of Missouri scientists, meanwhile, have been developing a super-healthy soybean oil.
So what’s a health-conscious consumer to do? “Soy can be very useful as a transitional food for people to eat while they’re changing from a traditional diet of animal proteins to a plant-based diet,” says Brendan Brazier, the Los Angeles–based author of The Thrive series of books on vegan-based training and a professional Ironman triathlete.
But that doesn’t mean that soy should be all you eat. “Soy is definitely part of a well-balanced diet but not the be-all, end-all of health,” says Keri Gans, MS, RD, CDN, a New York City–based spokesperson for the American Dietetic Association and author of The Small Change Diet (Gallery, 2011). “It can benefit you, but to what extent we’re not sure right now. More is not necessarily better, but the inclusion of soy is a plus.”
Both Brazier and Gans point out that the more that soy is processed and mixed with other ingredients, chances are it’s not as healthy for you. “Edamame is soy in its healthiest form because it is raw and unprocessed,” Brazier says. “Soy protein is a highly processed protein isolate, so it’s very acid forming and generally should be avoided.” Gans says that it’s safe to consume one to two servings of soy a day, in a whole-food form such as soy nuts or tofu.
As for supplements? Steer clear, especially if you have a history of breast cancer in the family, Gans suggests. “You could be getting too much estrogen,” she says. While extra estrogen doesn’t necessarily lead to breast cancer, phytoestrogens have been shown in laboratory studies to increase breast cancer cell growth, according to the research organization Susan G. Komen for the Cure. “Plus, from whole foods you’ll be getting the other micronutrients and phytochemicals that may be responsible for soy’s benefits.” She adds that people who consume too much soy (whether it’s organic, unprocessed or processed products) may be missing out on other important nutrients from other foods.
Things were certainly simpler a few decades ago when many of us reached for the bottle of soy sauce. Today, it’s important that we take a closer look at what soy has been scientifically shown to improve and be informed enough to recognize the things that it can’t.