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 beneficial.
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 diet.
December 10, 2005