A diet rich in soy may help feminine hearts, but timing matters, a new study has found.
Lifelong soy consumption, similar to the diet of women in Asia, produces the least atherosclerosis, a condition in which plaque builds up inside the arteries, researchers said.
Switching to a Western diet after menopause, similar to Asian migrants to North America, leads to just as much atherosclerosis as a lifelong Western diet, and switching to soy from a Western diet after menopause helps only if there is not much atherosclerosis already, researchers said.
Scientists at Wake Forest School of Medicine in Winston-Salem, reached the conclusions based on their feeding study of cynomolgus monkeys before and after surgical menopause.
They fed premenopausal monkeys a diet with protein derived mainly from animal sources or a diet with protein from high-isoflavone soybeans.
After having their ovaries removed, mimicking human menopause, one group of monkeys continued to eat a soy diet, another switched from animal protein to soy, a third group stuck with animal protein, and a fourth switched from animal protein to soy.
After 34 months, cholesterol levels were good in the monkeys who ate soy before and after menopause.
For those that switched to a soy protein diet after menopause, similar to some North American women concerned about their heart health, cholesterol levels did improve significantly.
But when it came to how much plaque progressed in the arteries, there were not any statistically significant differences, despite trends favouring a lifelong soy diet and the switch to soy after menopause.
As far as the total amount of atherosclerosis was concerned, monkeys eating a lifelong soy diet showed a much lower proportion of complicated plaque in the arteries than the other monkeys.
There was a big advantage to a postmenopausal switch to soy for some of the monkeys, however.
For those that had small plaques in the arteries at the time of menopause, the switch to soy after menopause markedly reduced the progression of plaque in the arteries.
The study was published in Menopause, the journal of The North American Menopause Society.
