— Pity the potato. It's widely blamed for the fattening of America. But a small new study found that daily consumption of a certain type of potato -- purple ones, that is --- can help lower blood pressure, without causing weight gain.
The research, conducted by Joe Vinson, a chemistry professor at the University of Scranton in Pennsylvania, tracked 18 overweight or obese, hypertensive subjects who either ate six to eight small purple potatoes, with skins, at both lunch and dinner (for a daily total of 218 calories), or had no potatoes as part of their "normal" diet for four weeks. Then the participants crossed over to the other regimen.
On average, diastolic blood pressure -- the bottom number in a blood pressure reading -- dropped by a statistically significant 4.3 percent and systolic blood pressure -- the top number in a blood pressure reading -- dropped by 3.5 percent.
While eating potatoes, most of the subjects -- even those on anti-hypertensive medications -- experienced lower blood pressure, and none of the subjects gained weight.
Although less popular than their white counterparts, purple potatoes — increasingly available at supermarkets, specialty food stores and farmers' markets — boast higher levels of polyphenol antioxidants that protect body cells against free radical damage that can increase disease risk. To preserve these powerful plant chemicals, subjects in Vinson’s study were asked to microwave their potatoes instead of using other cooking methods.
While research from larger sample sizes is needed, Vinson says the findings "provide at least some evidence that eating potatoes might be preventative like drinking coffee to reduce blood pressure." He notes that, like coffee, potatoes are high in a specific polyphenol called chlorogenic acid that has been shown to lower blood pressure in mice.
The study, not yet published, was presented this week at the American Chemical Society National Meeting in Denver.
The new research may help redeem the potato's nutritional rep. While a recent Harvard study found that having an extra daily serving of potatoes caused a small but significant weight gain (1 to 2 pounds) over a four year period, a closer look at the data reveals that weight gain from French fries was 6 times higher (3.35 pounds) than from boiled, baked, or mashed potatoes (0.6 pounds).
"The high cooking temperatures used to make French fries and potato chips seem to destroy most of the healthy substances in potatoes and leave mainly starch, fat and minerals," according to Vinson. Although the new study didn't include unfried red- and white-skinned potatoes, Vinson believes they will prove to produce similar body weight and blood pressure effects in future, larger human studies.
Indeed, potatoes can be a healthful addition to any diet, even if you’re trying to lose weight. They’re naturally low in calories, fat, cholesterol, and sodium, and rich in vitamins and minerals including vitamin C, an antioxidant that protects against cellular damage and potassium, a mineral that helps balance body fluids and negate possible blood pressure-raising effects of a high sodium diet. Potatoes also pack in fiber that may promote fullness and aid weight management.
To maximize possible nutritional and health benefits and minimize calories, lightly sauté, mash, or microwave potatoes instead of frying them and watch how you dress them. My favorite potatoes are red oven-roasted potatoes, cut in quarters, drizzled with extra virgin olive oil, some balsamic vinegar, and a pinch each of garlic and onion powder. Sweet potatoes cut into French fries and baked with a pinch of paprika and sea salt are also smart options.
Some recommendations for preparing potatoes from Jackie Newgent, R.D., author of "Big Green Cookbook:"