Potatoes definitely aren’t the poster child for diet food. Can we say empty calories and high-carb? But don’t cross America’s most-consumed vegetable off your menu yet. A new study being presented this week at the National Meeting & Exposition of the American Chemical Society suggests potatoes have at least one thing going for them: they’re pretty good at lowering blood pressure.

In the study, 18 overweight patients with high blood pressure ate two servings of potatoes a day. They specifically chose purple potatoes, since these Barney-colored spuds have a high concentration of a blood pressure-lowering chemical called chlorogenic acid.

Sure enough, after a month of potato eating, the patients reduced their blood pressure by 3.5 percent on the top number and 4.3 percent on the bottom number. And despite potatoes’ reputation as pounds-packers, none of the volunteers gained weight during the study.

Vinson says the results show that potatoes aren’t the diet demon they’ve been made out to be—that is, as long as they’re prepared correctly. Patients in the study ate plain microwaved potatoes with no butter, oil, sour cream, or any of the regular potato bar condiments. A single serving of microwaved potatoes has 10 percent of your daily vitamin C requirement, Vinson adds, and more potassium than a banana. And don’t toss the skins—they’re full of fiber.

Speaking of skins, even though the volunteers in this study ate purple potatoes, Vinson suspects that white- or red-skinned potatoes can also lower blood pressure. He’ll be checking that out in a future study.