WEDNESDAY, Aug. 31 (HealthDay News) -- French fries and potato chips may have given potatoes a bad rap, but new research finds the lowly tuber -- when cooked correctly -- may actually be good for the heart.

A small, pilot study suggests that a couple of servings of potatoes per day can lower blood pressure as much as oatmeal without causing weight gain, researchers said.

Joe Vinson, a professor of chemistry at the University of Scranton in Pennsylvania, analyzed 18 patients who ate six to eight small purple potatoes twice daily for a month and found their systolic and diastolic blood pressures (the top and bottom numbers on a blood pressure reading) dropped by 3.5 and 4.3 percent, respectively.

Most patients were either overweight or obese, and many were already taking medications for high blood pressure during the study, which was funded by the U.S. Department of Agriculture and was to be presented Wednesday at the national meeting of the American Chemical Society in Denver. Experts note that research presented at scientific meetings is preliminary and has not yet been peer-reviewed.

Vinson pointed out that potatoes can be a healthy food when they're not in the form of French fries or chips, or covered in high-fat toppings such as cheese and sour cream.

Purple ones, in particular, have high amounts of antioxidants, although red-skinned or white potatoes may have similar effects, he said.

The golf ball-sized potatoes used in the study were microwaved, which Vinson called a "benign" cooking method that doesn't add fat or calories or destroy healthy substances in potatoes.

"Everyone thought potatoes were just a starch and pretty much nothing else," said Vinson, explaining spuds' poor nutritional reputation. "I was surprised . . . a very large proportion (of participants) were taking medications and still we had a drop in blood pressure."

Lona Sandon, a spokesperson for the American Dietetic Association, said she wasn't surprised about the study results, noting that potatoes are an excellent source of potassium, which is known to help control blood pressure.

"I'm kind of glad to see someone saying something good about potatoes," said Sandon, also an assistant professor of nutrition at University of Texas Southwestern Medical Center at Dallas. "Potatoes are a pretty healthy staple food. They're nutritionally low in fat, relatively low in calories, and are loaded with nutrition, particularly in the skin."

Sandon noted that the study's small size made it difficult to draw solid conclusions and said that the skin of purple potatoes likely contains more of certain blood pressure-lowering antioxidants than those of white potatoes.

"The skin is key," she said. "That's where the nutrients are."

The purple potatoes used in the study are becoming increasingly available in supermarkets and specialty food stores, Vinson said.

More information

The U.S. Centers for Disease Control and Prevention has more about potatoes.