A diet rich in walnuts and walnut oil may prepare the body to deal better with stress, according to U.S. researchers. They looked at how these foods, which contain polyunsaturated fats, influence blood pressure at rest and under stress.
Previous studies have shown that omega-3 fatty acids — like the alpha linolenic acid found in walnuts and flax seeds — could reduce LDL (“bad”) cholesterol.
Now, it is known that people whose bodies have exaggerated responses to stress are at higher risk of heart disease. The new study’s goal: to see if omega-3 fatty acid from plants would deflect the heart’s responses to stress. To find out, they studied 22 healthy adults with high LDL cholesterol.
Researchers found that including walnuts and walnut oil in the diet lowered both resting blood pressure and blood pressure responses to stress. The stressors in the study were delivering a speech or immersing a foot in cold water. Notably, adding flax seed oil to the walnut diet did not further lower blood pressure.
The study is published in the current issue of the “Journal of the American College of Nutrition.” It may be the first to show that walnuts and the oil from them could reduce blood pressure during stress. This is important, because we can’t avoid all of the stressors in our daily lives.
Every person in the study followed three diets: 1) An “average” American diet without nuts, which reflects what the typical person in the U.S. consumes each day; 2) A diet with 1.3 ounces of walnuts and a tablespoon of walnut oil substituted for some of the fat and protein; 3) A diet including walnuts, walnut oil and 1.5 tablespoons of flaxseed oil. All three were matched for calories and specifically designed for each participant. The walnuts, walnut oil, and flax oil were either mixed into the diet in such offerings as muffins or salad dressing, or eaten as a snack. About 18 walnut halves or nine walnuts make up the average serving used by the researchers.
During the stressful activities, researchers took blood pressure readings from the participants. Results showed that average diastolic blood pressure — i.e. pressure in the arteries when the heart is resting — was significantly reduced when the people were on the diets containing walnuts and walnut oil.
Walnuts are a rich source of fiber, antioxidants, and unsaturated fatty acids, particularly alpha linolenic acid, an omega-3 fatty acid. These compounds could be responsible for the beneficial effects on blood pressure.