Soy has been consumed in Asia for centuries and enjoyed here in the U.S. for the last 50 years. Not only have they proved to be heart healthy, soyfoods also contain good-for-you nutrients such as complete protein, complex carbohydrates and unsaturated fats. Minimally processed soyfoods are also good sources of fiber, vitamins and minerals.
Yet, the Internet abounds with soy controversy. Mark Messina, world soy expert, and Stacey Krawczyk, National Soybean Research Laboratory research director, note that rumors of the negative health effects of soy are unfounded and often based on animal studies, are poorly designed or have statistically insignificant results.
With misinformation flourishing, the Minnesota Soybean Research & Promotion Council (MSR&PC) would like to take this opportunity during National Soyfoods Month (April) to debunk the myths surrounding soyfoods.
Does soy feminize boys and men? Clinical research says no. Consuming soy does not raise estrogen levels, nor does it decrease testosterone levels. Soy consumption does not affect sperm count. Studies with subjects drinking up to six glasses of soymilk a day – far more than recommended – proved no feminizing affects of soy on men or boys.
Does soy promote breast cancer? Twenty years of soy research have shown whole soyfoods to be safe for all women, including those at risk for breast cancer or who have had breast cancer. Exciting new research shows that young girls consuming soy can dramatically reduce risk of breast cancer later in life. Soyfoods do contain estrogen-like compounds, but any concern that this compound would increase the risk of breast cancer is based on animal studies. Krawczyk notes that "there is no human trial that has shown a link between eating soyfoods and any type of tumor recurrence or growth." Messina follows this up by saying that "Human studies show soyfoods are safe for all women."
Is soy formula safe for infants? Yes, says the American Association of Pediatrics. The only studies showing negative effects of soy formula were done on animals.
Do soyfoods cause dementia? Messina says, "There is no reason to believe that eating soyfoods is harmful to brain aging." This myth is based on the fear that eating soy reduces cognitive function and can cause brains to shrink. While one study suggested a link between tofu consumption and poorer cognitive function in old age, this was a study that did not show cause and effect. As well, it did not look at diet extensively enough to draw firm conclusions. There are no other studies to support it; in fact, three clinical studies suggest soy and isoflavones have beneficial effects on cognition.
Will consuming soyfoods block the absorption of minerals? Just like spinach (which does not get negative press), soy contains phytates and oxylates. These compounds can reduce the amount of minerals absorbed from foods eaten. But studies show that soy does not cause a reduction of minerals; conversely, soyfoods can actually be a strong source of many minerals.
Do soyfoods have adverse effects on the thyroid gland? This gland, found in the front of the throat, regulates metabolism and body temperature. Messina says, "Concerns about the anti-thyroid effects of soy are based primarily on in vitro and animal studies involving the soybean isoflavones." A review of 14 clinical trials concluded there was little evidence that soyfoods or isoflavones had an adverse affect on thyroid function in healthy human subjects. Studies published since this review have also found no effect on thyroid function.
Soy may be safe for healthy people, but is there connection between soy and hypothyroidism? Messina says that eating soy foods may increase the amount of thyroid medications needed for those who already have thyroid problems, but this would then hold true for many other healthy foods, as well.
There is no convincing evidence that eating moderate amounts of soyfoods will have negative health consequences; in fact, they offer many benefits. So why not give your diet a boost this month with nutritious and delicious soy!