Grape seed extract counters salt-hypertension

New findings suggest that a diet moderately high in grape seed extract can blunt salt-sensitive hypertension to the same extent as previous, potentially carcinogenic, treatments. A discovery which may be significant for the increasing number of women entering middle age.

Nearly two years ago, the Journal of the American Medical Association (JAMA) reported that women who took oestrogen for ten years or more after menopause were twice as likely to die of ovarian cancer as non-users.

According to the researchers, 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.

However a new research study, led by Ning Peng of the University of Alabama at Birmingham in the US, has found 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 oestrogens or 17ß-estradiol.

The researchers believe that this suggests that mechanisms other than the oestrogens receptor activation actually provides the beneficial effects of oestrogens therapy and that grape seed extract may be a useful supplement to blunt hypertension and other cardiovascular symptoms in postmenopausal women. The report adds that hypertension is strongly, continuously, and independently related to coronary artery disease (CAD), stroke, renal disease, and all-cause mortality.

Physiologists from Alabama previously found that plant oestrogens from soy reduce salt-sensitive hypertension in young, oestrogen-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 estrogens receptor mechanisms.

The ovaries were removed from spontaneously hypersensitive rats at three weeks of age and put on a phytoestrogen free (PE) diet containing high(8 per cent) or basal (1 per cent) sodium chloride. The researchersadded 0.5 per cent grape seed extract added to the food of the rats. Blood pressure and heart rate were measured telemetrically, and plasma PE concentrations were determined by mass spectrometry.

According to the researchers the results indicated that addition of grape seed extract to the diet has little effect on oestrogen-depleted female SHR on a normal diet that contains less than 1 per cent salt. But, whereas a high (8 per cent) salt diet greatly increased blood pressure in these rats, the addition of grape seed extract to the high salt diet greatly reduced the salt-sensitive rise in blood pressure in these oestrogen-depleted SHR. Also the researchers discovered that the addition of grape seed extract does not affect heart rate, suggesting that its blood pressure lowering effect is specific.

In conclusion the report notes that these results suggest that mechanisms other than the oestrogens receptor activation may underlie the beneficial effects of oestrogens therapy and that as a result grape seed extract may be a useful supplement to blunt hypertension in postmenopausal women.

'Antihypertensive Effects of Grape Seed Extract in Estrogen-Depleted Female Spontaneously Hypertensive Rats (SHR)' will be presented at Experimental Biology 2003, a meeting sponsored by the American Physiological Society, being held from 11 to 15 April 2003 at the San Diego Convention Center, California, in the US.