Incorporating walnuts into your diet may help you handle stress better, new research suggests.
Walnuts and walnut oil help reduce blood pressure during stressful situations because of the omega-3 fatty acids and anti-inflammatory compounds they contain, according to a study by a team of scientists at Penn State University.
Researchers looked at 22 healthy adult participants who had high levels of "bad" cholesterol known as LDL, or low density lipoproteins. They provided them with all their meals and snacks over the course of three different diet periods lasting six weeks each.
Some of the subjects were put on diets that included walnuts and walnut oil, and others were not. The study authors found that eating the nuts lowered both their resting blood pressure and their blood pressure responses to stressors they were exposed to in the lab -- giving a speech and soaking their feet in a tub of ice-cold water.
"This is the first study to show that walnuts and walnut oil reduce blood pressure during stress," author Sheila G. West, an associate professor of biobehavioral health, said in a statement. "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."
Walnuts contain a type of omega-3 fatty acid called alpha linolenic acid, which is also found in flax seeds. Prior research has shown that those omega-3s can reduce LDL cholesterol and markers including C-reactive proteins.
Strong reactions to stress can trigger a host of health problems including cardiovascular disease, according to the study, published in the current issue of the Journal of the American College of Nutrition.
"People who show an exaggerated biological response to stress are at higher risk of heart disease, "West said. "We wanted to find out if omega 3-fatty acids from plant sources would blunt cardiovascular responses to stress."
The blood pressure of participants on the walnut diet did not drop lower when flax seed oil was added, the authors found. But flax seed extract did seem to improve their vascular health -- gauged using a vascular ultrasound that measured the dilation of the arteries -- and reduce their C-reactive levels, causing a greater anti-inflammatory effect.
"Inflammation is a known factor in cardiovascular disease, stroke, et cetera," nutritionist Douglas Husbands told AOL Health. "To have a beneficial effect on inflammation, which those substances in walnuts and other nuts have, can be very powerful."
Each of the study participants followed each of the three diets in random order, taking a one-week break in between. They were tested at the end of every six-week interval.
One of the diets mimicked an "average" American diet without nuts. A second incorporated 1.3 ounces of walnuts -- which amounts to about nine of the nuts -- and a tablespoon of walnut oil in place of some of the fat and protein sources in the typical diet. The third included the walnuts and walnut oil with the addition of 1.5 tablespoons of flax seed oil. All three had an equal number of calories and didn't cause any weight changes in the subjects.
Once they'd completed each diet, the participants were given two different stress tests. For one, they were given a topic and two minutes to prepare a three-minute speech on it, which was videotaped. For the other, they had to immerse one foot in frigid water. Researchers took their blood pressure during the stress tests.
The subjects' average diastolic blood pressure was substantially lower when they were on the walnut-rich diets, according to the findings.
"These results are in agreement with several recent studies showing that walnuts can reduce cholesterol and blood pressure," said West. "This work suggests that blood pressure is also reduced when a person is exposed to stress in their daily life."
Husbands said the fat in walnuts helps ensure a beneficial proportion of hormones, which are derived from cholesterol, and the nuts' pH balance contributes to their anti-inflammatory effects.
"You don't want a low-fat diet -- you want a healthy-fat diet," he said.
The research was supported by The California Walnut Commission, the National Institutes of Health, and the Heart and Stroke Foundation in Canada.
by Catherine Donaldson