Are soybeans healthful or unhealthful
Are soybeans healthful or unhealthful?

Gabe Mirkin, M.D.

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 

For example, soybeans contain genistein, a weak estrogen that may 
help to prevent breast cancer. They contain omega-3 fatty acids that 
help prevent heart attacks, and are loaded with fiber that helps to 
prevent diabetes. But they also contain small amounts of trypsin 
inhibitors that increase risk for pancreatic damage and cancer in 
animals. Hemagglutinins in soybeans could cause clots to form and 
travel to the lungs. Goitrogens in soybeans block thyroid function 
to increase your need for that hormone. Estrogen-like genistein in 
soybeans could stimulate immature lobules in breast tissue of 
infants to increase risk for breast cancer many years later. 
Phytates in soybeans and many other plants can block the absorption 
of minerals. 

However, 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 

December 10, 2005