From The July 1999 Issue of Nutrition Science News
A woman's body goes through many changes during menopause—some of them with potential to affect cardiovascular health. When women's estrogen levels decrease during menopause, blood vessels can become rigid and less responsive to changes in blood flow and blood flow-altering mediators such as nitric oxide. Until now this decline in cardiovascular health was a risk women had to face if they opted against hormone replacement therapy. But research published in the March issue of The Journal of Clinical Endocrinology and Metabolism [1999;84(3):895-8] suggests that Promensil, an isoflavone-based dietary supplement derived from red clover, may help women maintain blood vessel elasticity and prevent hypertension during menopause. Novogen Inc. of Stamford, Conn., manufactures Promensil and supported the study.
Paul J. Nestel, M.D., and colleagues from the Cardiovascular Nutrition Laboratory at Baker Medical Research Institute in Victoria, Australia, tested the theory that dietary isoflavone intake could improve blood flow dynamics associated with menopause. In a double-blind, placebo-controlled trial, 17 women received placebo for three weeks—14 of them proceeded to take 40 mg isoflavones for five weeks, then 13 took 80 mg for five weeks. Three women served as controls, receiving placebo throughout. Arterial elasticity was measured by ultrasound after each stage. A 20 percent improvement in arterial elasticity was noted after the 40-mg dose compared with 24 percent after 80 mg and no change for those taking placebo. No side effects were associated with the isoflavone supplement. The 4 percent difference between the 40-mg and 80-mg doses was not statistically significant. Similar to a recent study with soy isoflavones, the researchers also found no significant effect on blood lipid fractions (HDL and LDL cholesterol and triglycerides) but did report a trend for favorable change.
"An important cardiovascular risk factor, artery elasticity, which diminishes with menopause, was significantly improved with red clover isoflavones," the authors wrote.
Promensil contains the isoflavones genistein, daidzein, biochanin and formononetin derived from red clover. Chickpeas and lentils are the only natural food sources of these four main estrogenic isoflavones. However, it would take 10 cups of chickpeas—which would also provide 2,600 calories—to get 40 mg of isoflavones. Soy, another food rich in isoflavones, provides only genistein and daidzein but has been shown by the same researchers, using equivalent isoflavone doses, to produce virtually identical effects on arterial compliance and lipids. This study was published in Arteriosclerosis, Thrombosis and Vascular Biology 1997; 17: 3392-3398