Study Shows Walnuts Are a Potent Source of Melatonin

SACRAMENTO, Calif., Sep 13, 2005 (BUSINESS WIRE) -- Many think melatonin is something you can take to fall asleep after long airplane flights, but scientists are studying how this powerful antioxidant actually fights diseases like cancer, may impact diseases associated with aging and likely will allow people to live healthier lives. Research at The University of Texas Health Science Center in San Antonio has proven walnuts are a natural source of melatonin.

According to Russel J. Reiter, Ph.D., Professor of Neuroendocrinology at The University of Texas Health Science Center at San Antonio, "The ingredients in walnuts would be expected to reduce the incidence of cancer, delay or make less severe neurodegenerative diseases of aging, including Parkinsonism, Alzheimer's disease and reduce the severity of cardiovascular disease." Published in the September issue of Nutrition: The International Journal of Applied and Basic Nutritional Sciences, the study is titled "Melatonin in walnuts: Influence on levels of melatonin and total antioxidant capacity of blood."

Dr. Reiter's study found walnuts are a potent source of melatonin, which is easily absorbed in the body. "When walnuts are consumed, blood levels of melatonin increase threefold," notes Reiter. Studies have shown walnuts reduce the risk of heart disease due to their combination of healthy nutrients, including omega-3 fatty acids and antioxidants. Reiter believes it is the synergy among the ingredients in walnuts -- the combination of nutrients plus the melatonin that makes them so beneficial. "Melatonin and omega-3s, both of which are in walnuts, starve cancers because they prevent the growth of cancer cells. When you take melatonin as a tablet, you are exclusively getting melatonin. I think the value of the walnut is the composite of what it contains."

University of Texas Health Science Center Press Release:

Walnuts contain melatonin, research shows

San Antonio (Sept. 13, 2005) -- The next time you reach for salad greens and dressing, you might consider adding some walnuts. New research out of The University of Texas Health Science Center at San Antonio shows that walnuts contain a fair amount of melatonin, a hormone that protects our cells against oxidative damage.

"Relatively few foods have been examined for their melatonin content," said Russel Reiter, Ph.D., professor of cellular and structural biology at the Health Science Center. "Our studies demonstrate that walnuts contain melatonin, that it is absorbed when it is eaten, and that it improves our ability to resist oxidative stress caused by toxic molecules called free radicals."

The research is reported in the September issue of the journal Nutrition.

Many diseases of aging, including cataracts, Alzheimer's disease and Parkinson's disease, have a free-radical component, Dr. Reiter said. A primary theory of aging states that aging and its associated degenerative changes are consequences of free-radical damage. Melatonin acts like a cellular "Pac-Man" gobbling up free radicals before they can cause harm.

"Melatonin is found in all vertebrates and invertebrates, even in algae, slime molds and bacteria," Dr. Reiter said. "In 1995, a couple of publications appeared showing that it also is present in plants. So, we not only produce it in our bodies, but we eat it in our diets."

Walnuts also contain large amounts of omega-3 fatty acids, which have been shown to inhibit certain types of cancer and to be heart healthy. Melatonin also has been shown to inhibit certain types of cancer. "Maybe these two ingredients complement each other," Dr. Reiter said. He plans an upcoming study to explore this synergistic effect.

Melatonin was first described in corn, tomatoes and potatoes, which have very little of it. Walnuts are a different story. "How many walnuts would you have to eat a day to benefit in terms of their melatonin content? We really don't know," Dr. Reiter said. "The bottom line is, now we know that walnuts have another ingredient that is healthy, namely, melatonin."

Eating a good, nutritious diet containing a variety of nutrient-rich foods is undoubtedly better than trying to get those beneficial ingredients from supplements. "It's the package deal," Dr. Reiter said. "In walnuts it's not only the melatonin that is healthy, but the other ingredients. It's really the composite of the nut that makes it healthy, not one ingredient."

Melatonin is perhaps more famous as a sleep aid. The pineal gland in the brain secretes a little of it during the day and more at night. The nighttime rise is most important. As we get older, our nighttime melatonin levels wane, often wreaking havoc on regular sleep patterns.

Free-radical damage increases as we age, while melatonin decreases. "I'm not going to suggest that if we boost our melatonin level we can defer age-related conditions," Dr. Reiter said. "But it is worth asking this question: Is the loss of melatonin, an important anti-oxidant, of any consequence in terms of us developing free-radical-related diseases? In the lab, we can use pure melatonin to forestall a lot of free-radical damage."

For example, adding melatonin to the diet of newborn rats that are susceptible to cataracts prevents cataracts from forming, he observed.

The finding that walnuts contain melatonin is important. "We don't know the half of it yet," Dr. Reiter said.

The California Walnut Industry provided a grant to support Dr. Reiter's research.

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