Walnuts have not only joined the ranks of smart foods, they are now at the top of the class. A recent study conducted by the University of Texas Health Science Center found that walnuts contain a significant amount of melatonin, a hormone that protects our cells against free radical damage (Nutrition, 2005, vol. 21, no. 9). Many diseases associated with aging, such as cataracts, Alzheimer’s, and Parkinson’s, have a free radical component that melatonin could help curb, says study author Russel J. Reiter, PhD. Melatonin, best known as a sleep hormone, has also been shown to decrease the risk of heart disease and inhibit breast, liver, and prostate cancers.

Relatively few foods have been examined for melatonin content. The discovery of the walnut/melatonin link is particularly exciting, Reiter says, because the melatonin in walnuts was shown to be absorbed efficiently, increasing blood levels of the hormone and immediately improving the body’s ability to resist oxidative stress. “The combination of the melatonin, the omega-3s, and the vitamin E found in walnuts is a very healthy package,” says Reiter.