Walnuts and Blueberries Improve Cognition, Says New Research
New research presented at Neuroscience 2007, the 37th annual meeting of the Society for Neuroscience , Nov. 3 to 7, provides food for thought, specifically regarding the role of walnuts and blueberries in diseases and aging that impairs brain function. Several presentations focused on the effects of these foods on improved brain health.
In “ Walnuts can improve motor and cognitive function in aged rats ,” (B. Shukitt-Hale, V. Cheng, D. F. Bielinski, J. A. Joseph; USDA/ARS, Human Nutrition Research Center on Aging, Boston), aged rats were fed diets containing 2%, 6% or 9% walnuts. These levels reversed several parameters of brain aging, as well as age-related motor and cognitive deficits. The 6% diet is equivalent to human consumption of 1 oz. walnuts daily, the recommended amount to reduce harmful low-density lipoprotein (LDL) cholesterol, and the 9% diet is equivalent to 1.5 oz. per day. “Importantly,” says researcher James Joseph, Ph.D., “this information, coupled with our previous studies, shows that the addition of walnuts, berries and grape juice to the diet may increase health span in aging and provide a ‘longevity dividend’ or economic benefit for slowing the aging process by reducing the incidence and delaying the onset of debilitating degenerative disease.” Previous research by Joseph and his colleagues showed high-antioxidant strawberry or blueberry extract diets also reversed age-related deficits in neuron function and in motor and cognitive behavior of rats.
Walnuts contain alpha-linolenic acid (ALA), an omega-3 fatty acid, and polyphenols that act as antioxidants that may block free radicals from producing compounds that increase inflammation. Study findings indicate these shorter-chain fatty acids may have beneficial effects on cognition, similar to those from long-chain fatty acids from sources such as fish. “The good news,” Joseph says, “is that it appears that compounds found in fruits and vegetables?and, as we have shown in our research, walnuts?may provide the necessary protection to prevent the demise of cognitive and motor function in aging.”
In “ Compounds in Alaska wild bog blueberries abolish neutral sphingomyelinase activation by TNFalpha in neuronal cells, ” (T. B. Kuhn, B. M. Barth, C. M. McGill, T. P. Clausen, S. J. Gustafson, University of Alaska, Fairbanks), the researchers presented data that show Alaska wild bog blueberries contain compounds that efficiently interfere with inflammatory processes in the central nervous system. The study found an interaction between compounds in Alaska blueberries and a protein in neuronal cells that reduces effects of inflammation. This information could lead to new drug therapies that would lessen brain and spinal-cord inflammation.
While fruits’ health benefits generally are attributed to antioxidant polyphenols, Thomas Kuhn, Ph.D., says that, surprisingly, the compounds in Alaska blueberries found in the study are neither antioxidants nor polyphenols, but work as specific inhibitors. “Expanding our knowledge of natural products’ health benefits and their molecular targets in the nervous system would improve preventative measures and potentially reveal new therapeutic strategies to alleviate inflammation in the brain and spinal cord,” he says. Brain and spinal-cord inflammation are associated with most chronic degenerative diseases such as Alzheimer’s, Parkinson’s, ALS or multiple sclerosis, and acute injuries including stroke and trauma.
In “Dietary enrichment with 2% blueberry extract to aged rats results in enhanced dendritic branching and spine neuroplasticity in cortical neurons and more complex brain circuitry,” (R. F. Mervis, P. Hwang, S. Antoine, J. Kotick, K. Kalmbach, B. Shukitt-Hale, J. Joseph; NeuroStructural Research Labs, Tampa, FL; Center for Aging and Brain Repair, University of South Florida, Tampa, FL; UDSA Human Nutrition Lab, Tufts University, Boston), researchers found supplementing the diet of old rats with 2% blueberry extract for 8 weeks resulted in maintenance and rejuvenation of brain circuitry. The 2% blueberry extract is equivalent to adding about half a cup of blueberries to a person’s daily diet.
The results showed that blueberries can not only protect against the loss of dendritic branching and dendritic spines (e.g., synapses) in aged animals, but can create neuroplastic enhancement of brain circuitry, causing it to resemble a much-younger brain. Blueberries contain polyphenols that may ease neuronal damage stemming from age-related oxidative stress and the formation of reactive oxygen species. Oxidative stress is thought to play a major role in age-related cognitive impairment.
Blueberries’ strong antioxidant and anti-inflammatory activities “along with other indirect mechanisms, may help to minimize, or reverse, the age-related breakdown of communication between neurons and optimize brain function in the old rat,” says researcher Ron Mervis, Ph.D., Center for Aging and Brain Repair, University of South Florida College of Medicine.