Soybeans healthful or harmful
Soybeans: healthful or harmful?

Gabe Mirkin, M.D.
A study from Tulane was widely reported in the news media to show 
that eating soybeans prevents heart attacks. That’s not what the 
study showed. The authors reviewed 41 recent articles on soybeans 
and blood cholesterol levels (American Journal of Cardiology, 
September 2006). They found that soybeans were unquestionably 
associated with lowering total cholesterol, the bad low-density 
cholesterol, and triglycerides, and increasing the good high-density 
cholesterol, and the more soybeans a person takes in, the greater 
the reduction in bad cholesterol. But no one has shown whether the 
benefits come from the soybeans themselves or from replacing other 
foods with soy products, which would reduce the amount of saturated 
fat, partially hydrogenated oils and cholesterol taken in. You might 
get the same results just by removing meat, chicken, full fat dairy 
products and so forth from your diet, even without eating any 

All plants contain chemicals that are healthful and chemicals that 
can harm us. Fortunately for us, our ancestors learned which plants 
are edible and healthful, and taught us to avoid those that are 
poisonous. However, if you eat very large amounts of one food, you 
can poison yourself, even though reasonable amounts are harmless or 
beneficial. For example, soybeans contain a plant estrogen called 
genistein, omega-3 fatty acids and fiber, all substances with known 
health benefits. But they also contain small amounts of trypsin 
inhibitors that could damage the pancreas; hemagglutinins that could 
cause clots to form; goitrogens that could block thyroid function; 
and phytates that can block the absorption of minerals. You would 
need to eat very large amounts of soy products to get any of these 
negative effects. Enjoy a moderate amount of soy foods, but do not 
let health claims lead you to eat huge amounts of soy to the 
exclusion of other foods. A healthful diet is a varied diet that 
includes plenty of vegetables, fruits, whole grains, beans and other 

January 15, 2007