The first study to check the effects of eating potatoes on blood pressure in humans has concluded that two small helpings of purple potatoes (Purple Majesty) a day decreases blood pressure by about 4 percent without causing weight gain. In a report in the ACS' Journal of Agricultural and Food Chemistry, the researchers say that decrease, although seemingly small, is sufficient to potentially reduce the risk of several forms of heart disease.
Joe Vinson and colleagues point out that people in the U.S. eat more potatoes than any other vegetable. Purple-skinned potatoes, a boutique variety increasingly available in food stores, are noted for having high levels of healthful antioxidant compounds. And in Korea, purple potatoes are renowned in folk medicine as a way to lose weight. Vinson's team thus decided to investigate the effects of eating 6-8 small microwaved purple potatoes twice a day on 18 volunteers, most of whom were overweight with high blood pressure. The volunteers ate potatoes or no potatoes for four weeks, and then switched to the opposite regimen for another four weeks while researchers monitored systolic and diastolic blood pressure (the higher and lower numbers in a blood pressure reading like 120/80), body weight and other health indicators.
Average diastolic blood pressure dropped by 4.3 percent and systolic pressure decreased by 3.5 percent. The majority of subjects took anti-hypertensive drugs and still had a reduction in blood pressure. None of the study participants gained weight. Vinson said that other studies have identified substances in potatoes with effects in the body similar to those of the well-known ACE-inhibitor medications, a mainstay for treating high blood pressure. But he suspects that the effects may be due to other substances in potatoes. The scientists do not know yet whether ordinary white potatoes have the same beneficial effects.
The authors acknowledge funding through a Cooperative Agreement Grant from the United States Department of Agriculture (USDA).