Grape Juice and High Blood Pressure

Evidence for grape juice having any impact on high blood pressure is contradictory, and the studies deal only with juice made from Concord grapes, and so it is not applicable to other types of grape juice. The Academy of Nutrition and Dietetics reports that red and purple grape juice helps lower blood pressure, reduces cholesterol and your risk of blood clots. In other words, drinking grape juice may be as beneficial to your heart as red wine.

History of Grape Juice
Grape juice as an industry began when Thomas Welch, having read of the recent discovery of Dr. Louis Pasteur, wondered if heating the juice of freshly pressed grapes to the boiling point and then bottling it in sterilized bottles would allow him to make unfermented wine for his church's communion services. He succeeded. It was his son, Charles Welch, who turned the invention into a business, known to this day as Welch's. The type of grape the Welches chose to use was the Concord grape, an American variety developed by Ephraim Wales Bull in Concord, Massachusetts, in 1854.

Good For The Heart
The French Paradox refers to an observation that the French people have a low incidence of cardiovascular disease despite a diet high in fat and cholesterol. The effect has tentatively been linked to consumption of red wine, a beverage found to be rich in a complex family of compounds called phenols or polyphenols. As shown by Mullen in the April 2007 issue of "The Journal of Agriculture and Food Chemistry," purple grape juice made with Concord grapes had the highest concentration of phenols of 13 fruit juices, whereas white grape juice had the lowest. What your own taste buds can tell you is juices high in polyphenols are more bitter and astringent.

Indirect Evidence
Mustali Dohadwala, in the November 2010 issue of "The American Journal of Clinical Nutrition," cited animal studies of grape juice and grape extracts lowering blood pressure in animal models. He also cited human studies demonstrating less artery stiffness and less risk of blood clotting. Theories of mechanism include increasing production of nitric oxide, which relaxes arteries, and reducing inflammation.

Direct Evidence
Two clinical trials directly measured the effect of drinking Concord grape juice on blood pressure. Dr. Dohadwala tested 20 ounces a day for eight weeks in mildly hypertensive adults and saw no benefit whatsoever compared with a calorie-matched placebo juice. Years earlier, Dr. YK Park reported in the spring issue of "Biofactors" that in a study conducted in South Korea, moderately hypertensive adults given 13 ounces of Concord grape juice a day for eight weeks had a 7 millimeters of mercury drop in systolic pressure and a 6 millimeters of mercury drop in diastolic blood pressure.

Concerns
With only two published human trials and contradictory results from those, there is no scientific consensus that Concord grape juice lowers blood pressure. Given that one of the recommendations from the American Heart Association is to lose weight, a juice that contains 150 calories per 8-ounce serving, all from sugar, has another strike against it beyond weak evidence. Yes, you can enjoy purple grape juice for its taste, just don't tell yourself you are in it for blood-pressure benefits.