American Physiological Society
April 10, 2003
Nearly two years ago, the Journal of the American Medical Association (JAMA) reported that women who took estrogen for ten years or more after menopause were twice as likely to die of ovarian cancer as nonusers. For the 20 million Americans who used estrogen alone or in combination therapy, the news reports have been devastating.
Many women immediately stopped taking the hormone. But if they were post-menopausal and hypertensive (had high blood pressure), they were abandoning a therapy that appeared to be useful in lowering blood pressure. Now, a new research study finds that a diet moderately high in grape seed extract can blunt salt (sodium chloride)-sensitive hypertension to about the same extent as treatment with either plant estrogens or 17ß-estradiol. This suggests that mechanisms other than the estrogen receptor activation actually provides the beneficial effects of estrogen therapy and that grape seed extract may be a useful supplement to blunt hypertension and other cardiovascular symptoms in postmenopausal women.
These findings may be significant for the increasing number of women entering middle age. It is estimated that between 40 and 50 million Americans have hypertension, which is indicated when an individual’s systolic or diastolic blood pressure is maintained above 140 mm Hg or 90 mm Hg, respectively. This debilitating medical disorder becomes more prevalent with increasing age, and at all ages and in both sexes it afflicts African-Americans more often than whites. Men with hypertension outnumber women with hypertension during young adulthood and early middle age, but hypertension rapidly increases in women after the age of menopause, and they soon outnumber men with hypertension.
Hypertension is strongly, continuously, and independently related to coronary artery disease (CAD), stroke, renal disease, and all-cause mortality. Past research has found that for every 7.5 mm Hg increase in diastolic blood pressure, the risk for coronary heart disease increases 29 percent and stroke risk increases 46 percent. These risks have been shown for women as well as for men.
A New Study
Physiologists from Alabama previously found that plant estrogens from soy reduce salt-sensitive hypertension in young, estrogen-depleted spontaneously hypertensive rats (SHR). In the current study this group examined whether the polyphenols in grape seed extract (primarily proanthocyandins) could provide the same result, indicating that the effects of the plant compounds might not simply be due to estrogen receptor mechanisms. The authors of “Antihypertensive Effects of Grape Seed Extract in Estrogen-Depleted Female Spontaneously Hypertensive Rats (SHR)” are Ning Peng, Nancy Brissie, and J.M. Wyss, all from the University of Alabama at Birmingham, Birmingham, AL. Their findings are being presented at Experimental Biology 2003, a meeting sponsored by the American Physiological Society, being held April 11-15, 2003, at the San Diego Convention Center, San Diego, CA.
The ovaries were removed from spontaneously hypersensitive rats at three weeks of age and put on a phytoestrogen free (PE) diet containing high (eight percent) or basal (one percent) sodium chloride. The researchers added 0.5 percent grape seed extract added to the food of ½ the rats. Blood pressure and heart rate were measured telemetrically, and plasma PE concentrations were determined by mass spectrometry.
The research results indicated the following:
Addition of grape seed extract to the diet has little effect on estrogen-depleted female SHR on a normal diet that contains less than 1% salt.
A high (8%) salt diet greatly increases blood pressure in these rats, but the addition of grape seed extract to the high salt diet greatly reduces the salt-sensitive rise in blood pressure in these estrogen-depleted SHR. The addition of grape seed extract does not affect heart rate, suggesting that its blood pressure lowering effect is specific.
These research findings indicate that in estrogen-depleted SHR, grape seed extract blunts the hypertensive effects of a high salt diet to about the same extent as treatment with either endogenous or dietary estrogens. None of the three compounds effects heart rate.
This suggests that mechanisms other than the estrogen receptor activation may underlie the beneficial effects of estrogen therapy and that grape seed extract may be a useful supplement to blunt hypertension in postmenopausal women.