Scientists have known for years that women are protected from cardiovascular disease before menopause, but their risk increases significantly after menopause.
Although estrogen is thought to be the protective factor, post-menopausal hormone replacement therapy remains controversial due to the side effects.
In an effort to find a safer and more effective therapeutic option, scientists at Wake Forest Baptist Medical Center conducted an animal study to determine whether a high soy protein diet reduced the risk of coronary artery atherosclerosis, hardening and narrowing of the arteries, after menopause. Lifelong soy consumption, similar to the diet of women in Asia, produces the least atherosclerosis, they found. 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 isn't much atherosclerosis already.
“If started before menopause, we found that soy significantly prevents atherosclerosis, one of the leading causes of cardiovascular disease,” said Giselle Meléndez, M.D., an instructor of cardiology at Wake Forest Baptist and lead author of the study. “Soy-rich diets contain isoflavones, estrogen-like compounds that have been postulated to be cardioprotective. Their molecular structure resembles that of estrogen and may act through the same receptors in the body. The key here is beginning soy supplementation (about 25 g per day) before menopause and substitute the consumption of proteins derived from animal sources with soy-rich products.”
Researchers reached those 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. And 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 (with lower total, LDL, and VLDL and higher HDL). But when it came to how much plaque progressed in the arteries, there weren't any statistically significant differences, despite trends favoring 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.
These findings add to the similar ones from the Women's Isoflavone Soy Health (WISH) clinical trial on atherosclerosis in women after menopause, but this animal study was able to model what the effects of a soy diet or soy supplements may be, based on women's diets and heart health before menopause or very early after menopause, when artery plaques may still be small.
"This study underscores how important it is for women to get into the best cardiovascular shape they can before menopause. The healthy habits they start then will carry them through the years to come," says NAMS Executive Director Margery Gass, MD.
Article: "Beneficial effects of soy supplementation on postmenopausal atherosclerosis are dependent on pretreatment stage of plaque progression," Menopause. Source: Wake Forest School of Medicine
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