Walnuts, the brain shaped nuts, cut down cholesterol and may also help fight stress and reduce blood pressure.
Those with high levels of bad cholesterol had lower blood pressure during stressful moments after following a diet rich in walnuts for three weeks.
Study participants were told to deliver a three-minute speech or sink one foot in cold water - both of which trigger stress.
Those who ate walnuts had lower blood pressure, said Professor Sheila West from the Penn State University in the US, according to the
"This is the first study to show that walnuts reduce blood pressure during stress. People who show an exaggerated biological response to stress are at higher risk of heart disease," she said.
The team used three diets - one without nuts, one with walnuts and walnut oil and a third with walnuts and flaxseed oil, according to the Journal of the American College of Nutrition.
Adding flaxseed oil did not affect blood pressure, but did help create an anti-inflammatory effect in arteries. This could reduce the risk of heart disease, the researchers say.
After each diet, the subjects were asked to take the speech and cold-water stress tests.
Average diastolic blood pressure - the 'bottom number' or the pressure in the arteries when the heart is resting - was significantly reduced for those on diets containing walnuts and walnut oil.
West added: "These results are in agreement with several recent studies showing that walnuts can reduce cholesterol and blood pressure."