Walnuts, walnut oil, improve reaction to stress
A diet rich in walnuts and walnut oil may prepare the body to deal better with stress, according to a team of Penn state researchers who 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 -- can reduce low density lipoproteins (ldl) -- bad cholesterol. These foods may also reduce c-reactive protein and other markers of inflammation.
"People who show an exaggerated biological response to stress are at higher risk of heart disease," said sheila G. West, associate professor of biobehavioral health. "We wanted to find out if omega 3-fatty acids from plant sources would blunt cardiovascular responses to stress." The researchers studied 22 healthy adults with elevated ldl cholesterol. All meals and snacks were provided during three diet periods of six weeks each.
The researchers found that including walnuts and walnut oil in the diet lowered both resting blood pressure and blood pressure responses to stress in the laboratory. Participants gave a speech or immersed their foot in cold water as a stressor. Adding flax seed oil to the walnut diet did not further lower blood pressure.
Walnuts are a rich source of fibre, antioxidants, and unsaturated fatty acids, particularly alpha linolenic acid, an omega-3 fatty acid, and these compounds could be responsible for the beneficial effects on blood pressure. flax oil is a more concentrated source of omega-3 fatty acids than walnut oil, but this study did not test whether flax oil alone could blunt cardiovascular responses to stress.
"These results are in agreement with several recent studies showing that walnuts can reduce cholesterol and blood pressure," noted West. "This work suggests that blood pressure is also reduced when a person is exposed to stress in their daily life."