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). 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.
"This is the first study to show that walnuts and walnut oil reduce blood pressure during stress," said West. "This is important because we can't avoid all of the stressors in our daily lives. This study shows that a dietary change could help our bodies better respond to stress."
A subset of the participants also underwent a vascular ultrasound in order to measure artery dilation. Results showed that adding flax oil to the walnut diet significantly improved this test of vascular health. The flax plus walnuts diet also lowered c-reactive protein, indicating an anti-inflammatory effect. According to West, that could also reduce risk of cardiovascular disease.
The researchers used a randomized, crossover study design. Tests were conducted at the end of each six-week diet, and every participant consumed each of the three diets in random order, with a one-week break between. The diets were matched for calories and were specifically designed for each participant so that no weight loss or gain occurred.
The walnuts, walnut oil, and flax oil were either mixed into the food in such offerings as muffins or salad dressing or eaten as a snack. About 18 walnut halves or 9 walnuts make up the average serving used by the researchers.
After each diet, the participants underwent two stress tests. Throughout these tests, the researchers took blood pressure readings from the participants. Results showed that average diastolic blood pressure was significantly reduced during the diets containing walnuts and walnut oil.
MEDICA.de; Source: Penn State