Dietary Intervention Shows Neuroprotection
By Rosalie Marion
Bliss March 31, 2009
Adding a moderate, but not high, amount of walnuts to an otherwise
healthy diet may help older individuals improve performance on tasks that
require motor and behavioral skills, according to an animal model study by
Agricultural Research Service
(ARS)-funded scientists. Walnuts contain polyphenols and other antioxidants and
essential fatty acids.
The study was conducted by researchers with the
Mayer USDA Human Nutrition Research Center on Aging (HNRCA) at
Tufts University in Boston, Mass.
Shukitt-Hale and coauthors Lauren Willis and Vivian Cheng reported the
study in the
Journal of Nutrition. They are with the HNRCA's Neuroscience Laboratory.
ARS is the principal intramural scientific research agency of the
U.S. Department of Agriculture.
The aging brain undergoes many changes that can result in altered or
impaired neuronal functioning. Such disruption can be attributed in part to
alterations in "synaptic plasticity," or the ability of the connections between
neurons to change in strength and function, and also by increased oxidative
damage to neural tissue. In aged rodents, these impairments are seen as poor
performance on age-sensitive tests of balance, coordination, and "spatial"
For the study, weight-matched, aged rats were randomly assigned to one
of four diet groups. For eight weeks, the rats were fed special chow mixes that
contained either 2 percent, 6 percent or 9 percent walnuts-or no walnuts-before
undergoing motor and memory tests. For comparison, the 6 percent walnut study
diet is equivalent to a human eating 1 ounce, or about 7 to 9 walnuts, a day.
That counts as both a 2-ounce equivalent from the "meat and beans group" and 2
teaspoons toward a daily allowance of dietary oil, as described at
The study found that in aged rats, the diets containing 2 percent or 6
percent walnuts were able to improve age-related motor and cognitive
shortfalls, while the 9 percent walnut diet impaired reference memory. Walnuts,
eaten in moderation, appear to be among other foods containing polyphenols and
bioactive substances that exhibit multiple effects on neural tissue, according
to the researchers.