Are you getting palpitations about an upcoming presentation at work or a looming visit from your least favorite relatives? To help your body cope with the stress you know is headed your way, start popping a daily handful of walnuts a few weeks in advance of the fray. Better yet, have a handful every day regardless, as new research demonstrates that walnuts and walnut oil reduce blood pressure when you are under stress... and even during those all-too-rare, happy moments of calm.
YOUR COPING MECHANISM
Earlier studies had already shown that nuts reduce resting blood pressure -- in other words, when people are not under stress. So at The Pennsylvania State University, researchers undertook the study of walnuts’ impact on people when they deliberately exposed study subjects to psychological and physical stress. "People who show an exaggerated biological response to stress are at higher risk for heart disease," explains study author Sheila G. West, PhD, an associate professor of biobehavioral health.
The researchers provided 22 adults who had elevated levels of LDL cholesterol (the so-called "bad" type of cholesterol) with all their meals and snacks during three separate six-week periods. The diets included...
- A control diet. An "average" American diet, which was defined as 50% carbohydrates, 16% protein and more than 30% fat, but with no nuts.
- A walnut diet. The same control diet as above, but with a handful of walnut halves (totaling 1.3 ounces -- 18 halves) and a tablespoon of walnut oil daily in place of some of the saturated fat and protein in the control diet.
- A walnut/flaxseed diet. The walnut/walnut oil diet plus 1.5 tablespoons of flaxseed oil daily.
Participants ate walnuts as a snack, while the walnut oil and flaxseed oil were mixed into food items such as salad dressing and muffins. Researchers matched the three diets for calories and designed them to generate neither weight loss nor weight gain. After participants ate the diets for six weeks, researchers raised participants’ stress levels in two ways...
- Psychological stress. In the first situation, participants were given just two minutes to prepare and three minutes to deliver a speech while being videotaped.
- Physical stress. In the second situation, participants put one of their feet into ice cold water for two and a half minutes.
The result: During each stress test, investigators measured individuals’ blood pressure. And good news -- they found that stress-induced blood pressure was two to three points lower in those who ate the two walnut diets.
The walnut/flaxseed diet did not lower blood pressure any further than the walnut diet. However, it reduced inflammation and LDL cholesterol and increased vascular dilation responses -- small changes that together confer a cardiovascular health benefit, according to Dr. West.
These findings were published in the December 2010 issue of the Journal of the American College of Nutrition.
While a two- or three-point improvement in your blood pressure may not seem like a lot, the walnut diets also lowered LDL cholesterol and reduced constriction of blood vessels throughout the body as measured by blood tests (lipid profiles) and vascular ultrasound. And while this particular study looked at individuals with elevated cholesterol, many other trials demonstrate that walnuts offer valuable health dividends for us all.
Walnuts are rich in antioxidants, fiber and polyunsaturated fatty acids such as alpha-linolenic acid (ALA, an omega-3 fatty acid), and researchers believe that these components may be responsible for the positive impact in blood pressure.
What You Can Do
Enjoy one serving of walnuts daily instead of a handful of chips or a couple of cookies. Keep in mind, of course, that you can’t rely on any one magic food or supplement or exercise to control blood pressure or put a lid on stress. That said, walnuts can be one tasty and healthful daily addition to your diet.
Sheila G. West, PhD, an associate professor of biobehavioral health, The Pennsylvania State University, University Park, Pennsylvania.