Oct. 8, 2004 -- Premenopausal women may want to start eating more soy to protect their heart and bones for years to come, according to new research.
Jay Kaplan, PhD, and Cynthia Lees, DVM, PhD, at Wake Forest University Baptist Medical Center, worked with colleagues on two new soy studies. They presented their findings at the 15th annual meeting of the North American Menopause Society, held this week in Washington.
Soy has attracted a lot of research attention in recent years, and the jury is still out on its effects. Earlier this week, a report indicated that soy-based foods and extracts might not help women avoid hot flashes and other menopausal symptoms. However, soy may help the hearts and bones of premenopausal women, say Kaplan and Lees.
The researchers each studied soy's effects on 100 fully developed, premenopausal monkeys. Some monkeys were at higher risk for heart disease due to the stress of their low social rank in their community's pecking order.
Lees and Kaplan each gave half of their monkeys a soy-rich diet containing the human equivalent of 129 milligrams per day of isoflavones, soy's key ingredient. That's much more soy than most Americans eat. In fact, it's about twice as much as typical levels in soy-rich Asian diets, according to a news release.
In both tests, the soy-eating monkeys got all of their protein from soy for one year. A second group of monkeys didn't eat any soy, consuming all their dietary protein from animal sources including milk.
Soy helped the monkeys' hearts.
Monkeys at high risk for heart disease fared best, lowering their ratio by 48%, compared with monkeys that did not eat soy.
The benefit was not as strong in the soy-eating monkeys at lower risk for heart disease. They had a 33% drop in their ratio of total cholesterol to HDL cholesterol, compared with monkeys not eating soy.
"Soy seems to provide potent protection in monkeys, in terms of cholesterol levels. We presume the benefit would apply to premenopausal women as well."
Soy also strengthened bones, says Lees.
The monkeys already had fully developed skeletons. Still, they all gained bone after 12 months. However, the soy eaters gained more bone than the comparison group. The extra bone density could come in handy after menopause, helping preserve bone and lower the risk of bone thinning osteoporosis.
"This suggests the possibility that if women consumed soy on a regular basis before menopause, it could benefit their health after menopause," says Lees in a news release.
No word yet on the exact amount of soy needed for humans, and which sources might work best.