For people trying to stick to a healthy diet, fats are generally high on the list of nutrients to avoid.

However, a recent Penn State study shows that alpha-linolenic acid (ALA), an unsaturated fatty acid found in walnuts and other sources, can help to reduce risks of heart disease, said Penny Kris-Etherton, professor of nutrition and member of the research team.

ALA decreases many known risk factors for heart disease, including blood cholesterol and triglycerides, she said.

Kris-Etherton said this new study also shows this fatty acid decreases cardiovascular disease risks by preventing inflammation of the blood vessels.

A diet high in walnuts or other foods that are high in ALA decreases C-reactive protein (CRP), which is a marker for inflammation and a risk factor, she said.

"Some people think that an inflammatory state is the underlying basis for heart disease," Kris-Etherton added.

Keith Martin, assistant professor of nutrition, said inflammation can cause plaque formation, which may lead to heart disease. ALA inhibits inflammation, he added.

"Alpha-linolenic acid doesn't just lower cholesterol, but it also positively alters the way blood vessels respond to inflammatory stimuli," Martin said.

The study included 20 men and three women who were overweight, had moderate to high cholesterol levels and weren't taking any dietary supplements or medications that lower cholesterol.

"We wanted participants who were at high risk for heart disease," Kris-Etherton said.

The participants were separated into three groups, and each group followed a particular diet for six weeks: the average American diet, a diet high in ALA, and a diet high in linoleic acid (LA), which is another type of unsaturated fatty acid.

The diets rich in these fatty acids decreased total cholesterol levels by 11 percent, and CRP levels declined more for participants on the ALA diet than the LA diet, according to the study.

Martin said ALA is also found in soybean oil and canola oil, and they contain as much of the fatty acid as walnuts do.

However, "the good thing about walnuts is that they are a whole food and contain other potentially beneficial components that may not be found in the oil itself," he said.

Martin said canola oil is better to use for cooking than vegetable oil because it contains a higher amount of unsaturated fatty acids.

Compared with other oils, soybean oil is also a better source of phyto-chemicals, which are disease-preventing compounds that boost the immune system, he said.

"All fats have a lot of calories, so it's best to pick an oil that is healthier for you," Martin said. "I think Americans are getting plenty of fat in their diets, but they may want to replace less desirable fat sources for ones that are high in ALA. For example, instead of getting fat from french-fry oil, one might instead replace that with a handful of walnuts."

Terry Etherton, professor of animal nutrition, said people still need to be mindful of calorie control when planning their diets, even though certain fats are beneficial in reducing risks of heart disease.

"Fats are the most calorie-dense [source of energy], with twice the caloric density of proteins and carbohydrates," he said.

Etherton said although some people promote a diet low in fat as the most heart-healthy diet, he doesn't think this is necessarily true in all cases.

"A diet higher in healthy fat can be part of a heart-healthy diet and may also be more palatable than a diet low in fat," he said.