Facts versus beliefs

Why is there still a question mark about soyfoods? Some put more stock in the wizardry of cell phones than the science of food.

Surprisingly, society is questioning what used to be scientific fact. Note the controversies over pasteurizing milk to prevent illness related to E. coli or listeria and immunizing children to prevent whooping cough or measles. That same reticence to believe science is found in the polls about soyfoods.

In the recent edition of SoyConnection, Dr. Mark Messina noted the results of an American survey in which a vast majority of health professionals view soyfoods positively but just over half of the public concurs. Misconceptions continue about male feminization, soy and breast cancer, thyroid function and fertility.

I can’t think of any other food — other than peanuts — that elicits as much emotion. Here’s the bottom line on these four subjects of concern.

On male feminization

Clinical studies show neither soyfoods nor isoflavones affect testosterone levels or sperm or semen parameters or otherwise exert feminizing effects. In addition, soy protein enhances lean tissue accretion and strength in response to resistance exercise.

Soy and breast cancer patients

Clinical studies investigating the effects on markers of breast cancer risk, and epidemiologic studies evaluating recurrence and mortality, show that soyfoods can be safely consumed by women with breast cancer.

Thyroid function

Clinical studies show neither soyfoods nor isoflavone supplements adversely affect thyroid function in healthy individuals with a normal functioning thyroid even when exposure occurs over several years and greatly exceeds typical Japanese intake.


Clinical studies show soy does not prevent ovulation or appreciably affect reproductive hormones in premenopausal women. Epidemiologic data suggest soy intake may negate the harmful effects of BPA on live birth rates in women undergoing assisted reproductive technology. In men, clinical studies show neither soy nor isoflavones affect sperm or semen parameters and epidemiologic data show male soy intake doesn’t affect in vitro fertilization rates in their partners.

These findings affirm the safety of soyfoods. Period.