Any way you crack them, walnuts are a healthy addition to your diet. The two bumpy lobes of the walnut kernel look similar to the human brain, a resemblance that long ago gave walnuts a reputation as "brain food." In the 16th and 17th centuries, the hearty tree nut was used to treat head ailments, boost intellect and calm emotions. Today, research shows that consuming walnuts can indeed improve cognitive function, as well as provide protective benefits against a host of illnesses, including cardiovascular disease and certain cancers.
Walnuts owe many of their numerous health benefits to their rich supply of omega-3 fatty acids. Omega-3s are protective fats that the body cannot manufacture itself. Aside from nuts and cold-water fish, the typical American diet is almost devoid of omega-3s, and researchers estimate that up to 60 percent of Americans are deficient in this essential fatty acid. Omega-3s benefit the cardiovascular system by preventing erratic heart rhythms and blood clots, improving the ratio of HDL (good) cholesterol to LDL (bad) cholesterol, lowering blood pressure, and reducing inflammation, which can turn cholesterol into artery-clogging plaque. Accordingly, studies demonstrate that walnut-rich diets can improve cholesterol ratios, increase the elasticity of the arteries, and reduce cardiovascular risk factors such as inflammation.
Omega-3s are also important for proper brain cell function. Low dietary intake of omega-3s is associated with increased rates of depression and, in children, with hyperactivity, learning disorders, and behavioral and sleep problems. Adding a moderate amount of walnuts to an otherwise healthy diet may improve neural function across the lifespan, especially in older adults. As a result of the aging process, brain cells lose synaptic plasticity — the ability of the connections between neurons to change in strength and function. In animal studies, adding walnuts to the diet of aged rats helped correct motor and cognitive deficits.
In addition to omega-3s, walnuts are also rich in monounsaturated fats. These healthful fats, a cornerstone of the Mediterranean diet, have been shown to reduce cholesterol levels. A study conducted in Spain compared the effects of a low-calorie Mediterranean diet to one in which walnuts were substituted for one third of the calories supplied by olives and other monounsaturated fats. Total cholesterol as well as LDL cholesterol were significantly reduced among those in the walnut diet group.
Health Benefits — Walnuts:
- contain antioxidants like L-arginine, which keeps blood vessels relaxed, and melatonin, which helps regulate sleep
- contain phytosterols that bind to estrogen receptors, which may help slow tumor growth and reduce cancer risk
- are high in omega-3 fatty acids, which help regulate heart rhythm, prevent blood clots and reduce inflammation
- monounsaturated fat content helps reduce cholesterol levels
Walnuts are also dense with antioxidants and essential amino acids. A 2002 study conducted in Norway showed that walnuts rank second only to rose hips in their antioxidant content. Ellagic acid, an antioxidant, supports the immune system and has anticancer properties. L-arginine, an essential amino acid, is converted to nitric oxide in the body, helping to keep blood vessels smooth and relaxed. Melatonin, a powerful antioxidant, helps regulate sleep and reduces free radical damage. Animal studies have demonstrated that eating walnuts can triple blood levels of melatonin.
The phytosterols in walnuts bind to estrogen receptors and therefore may prevent or slow the growth of breast cancer tumors fueled by estrogen. In animal studies, walnuts cut the risk of breast cancer; when it did develop, walnuts helped curb tumor growth.
Packed with so many health-promoting compounds – omega-3s, monounsaturated fats, antioxidants, and phytosterols, not to mention minerals including manganese and copper–walnuts are powerhouses of nutrition. The brain-shaped nut may not literally make you smarter as early physicians believed, but adding walnuts to your diet is undeniably a smart choice.
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(Updated: 11/19/12 SG)