How Good Is Soy?
A little does a lot.
June 26, 2000 -- Awakening to the sound of a whirring blender and the sharp
scent of fresh soybeans on Saturday mornings meant only one thing: a breakfast
of Grandma's warm, sweet soy milk. I loved to sit and watch as she squeezed the
milk out of ground soybeans wrapped in a cheesecloth.
Countless glasses later, I discovered that soy milk has a lot more to offer
than fond childhood memories. Packed in every yellow bean are estrogen-like
molecules, called isoflavones, which may help fight heart disease,
osteoporosis, cancer, and other diseases. Based on just some of the latest
findings, the Food and Drug Administration last year gave food makers
permission to extol soy's cholesterol-lowering prowess on package labels.
That's great, if you happen to believe soy is a healthy choice for everyone.
But with soy showing up in everything from breakfast cereal and pasta to energy
bars and smoothies, some researchers now worry that too much of a good thing
could be harmful.
"People ought to know that there ain't no free lunch," says Lon
White, MD, MPH, senior neuroepidemiologist at the University of Hawaii. "At
some point -- if these molecules are as potent as [we think] they are -- there
will be potent [adverse] effects."
White, for one, worries that soy may speed the aging of brain cells. He
recently found evidence that the brains of elderly people who ate tofu at least
twice a week for 30 years were aging faster than normal. Tests designed to
assess memory and analytical ability showed that their brains functioned as if
they were four years older than their actual age, White says of his study
published in the April 2000 issue of the Journal of the American College of
Another fear is that the estrogen-like substances in soy may dampen the
function of the thyroid. Consuming 40 milligrams of isoflavones a day can slow
the production of thyroid hormone, says Larrian Gillespie, MD, author of The
Menopause Diet and The Goddess Diet. (One tablespoon of soy powder
contains about 25 milligrams of isoflavones, while most isoflavone supplements
come in 40-milligram pills.)
According to Gillespie, within a few weeks of regularly consuming 40
milligrams of isoflavones, some women feel fatigued, constipated, and achy all
over. Some also gain weight and have heavier menstrual periods. Menopausal
women are at particular risk, since they're already prone to hypothyroidism.
"Women think it's because of hormones and don't realize they're symptoms of
hypothyroidism," Gillespie says. "Once they stop the soy, they say,
'I'm feeling fine again.' "
Soy's Not All Bad
But if some studies point to dangers from soy, others suggest important
benefits. For instance, isoflavones may prevent the growth of
estrogen-dependent breast cancer cells, according to findings published in the
March 2000 issue of the journal Cancer Research. That's because
isoflavones appear to encourage the body to break down estrogen more quickly --
before it can stimulate cancer cells to grow. Instead of lingering in the
blood, bits and pieces of estrogen molecules wind up in the urine.