Almost every food has its time in the spotlight as the new "super food"--eggs, milk, coffee, chocolate, red wine and countless others. At any one time, magazine articles, newspaper headlines and TV segments praise a food's amazing benefits; then a few months later (or sometimes even days or weeks), a completely new set messages come out proposing the exact opposite.
Now it's soy's turn. For years, we heard nothing but positive things about soy's cancer-fighting, heart-healthy and overall health benefits. Lately, however, word on the street is that some of those healthful claims about soy are overstated, while some are even perpetuating myths like soy does more harm than good.
Although a few negative claims have surfaced recently, there's no need to banish soy from your diet. Let's look at some of the most widely held soy-related myths and the research that shows that soy continues to be a healthy choice.
Claim #1: Soy Contributes to Cancer Growth
Soybeans are rich in isoflavones, compounds that are similar to the female hormone estrogen. In some tissues, these substances mimic the action of estrogen, while in others they block the action. Recent studies on the effect of isoflavones are conflicting: Some research suggests they may reduce cancer growth, while others suggest their estrogenic activity could contribute to cancer growth.
A 2008 study in the Nutrition Journal stated that there is little clinical evidence to suggest that isoflavones increase the risk of breast cancer in healthy women or worsen the prognosis of breast cancer patients. (1)
Although a few recent studies have shown that soy may not offer the level of protection against cancer as once thought, other recent studies still suggest that soy plays a protective role against some cancers, including breast, colorectal and prostate cancers. (2-4)
Moderate intake of dietary soy is safe, though the safety of concentrated soy supplements (e.g., pills, powders) needs further study. The American Cancer Society continues to state on their website that eating or drinking soy products is considered safe for those who aren't allergic to soy, and notes that using soy foods as a substitute for some servings of animal protein is one way to reduce red meat and animal fat intake.
Nancy Clark, M.S., R.D., author of Nancy Clark's Sports Nutrition Guidebook, notes "just don't expect the soy alternative to taste like red meat. That is, don't expect the soy burger to taste like a hamburger."
Claim #2: Soy Has No Positive Effect on Cardiovascular Health
After a careful review of human studies, in 1999 the FDA gave permission for manufacturers to include a claim on their food labels that a daily intake of 25 grams of soy protein may reduce heart disease risk. Today, the degree of soy's positive effect on heart health has come into question.
A recent study reviewed the findings in a majority of 22 randomized trials in which isolated soy protein with isolflavones (compared with milk or other proteins) decreased LDL cholesterol on average by just three percent, down from an earlier study's findings of 12.9 percent. (5,6)
Although the more recent study showed a less significant effect on cholesterol, it still concluded that soy's fiber, vitamins, minerals and low content of saturated fat can benefit cardiovascular and overall health. In addition, a 2005 study concluded that soy protein can reduce blood pressure and may help prevent and treat hypertension, a leading risk factor for heart disease.