British Journal of Nutrition

Short Communication

Dose-dependent effects of walnuts on motor and cognitive function in aged rats

Lauren M. Willisa1, Barbara Shukitt-Halea1, Vivian Chenga1 and James A. Josepha1 c1

a1 USDA-ARS, Human Nutrition Research Center on Aging at Tufts University, 711 Washington Street, Boston, MA 02111, USA


Aged rats show decrements in performance on motor and cognitive tasks that require the use of spatial learning and memory. Previously we have shown that these deficits can be reversed by the polyphenolics in fruits and vegetables. Walnuts, which contain the n-3 fatty acids α-linolenic acid and linoleic acid, are a dietary source of polyphenols, antioxidants and lipids. Thus, the present study examined the effects of walnut supplementation on motor and cognitive ability in aged rats. Fischer 344 rats, aged 19 months, were fed a control, or a 2, 6 or 9 % walnut diet for 8 weeks before motor and cognitive testing. Results for the motor testing showed that the 2 % walnut diet improved performance on rod walking, while the 6 % walnut diet improved performance on the medium plank walk; the higher dose of the 9 % walnut diet did not improve psychomotor performance and on the large plank actually impaired performance. All of the walnut diets improved working memory in the Morris water maze, although the 9 % diet showed impaired reference memory. These findings show for the first time that moderate dietary walnut supplementation can improve cognitive and motor performance in aged rats.

(Received March 25 2008)

(Revised June 11 2008)

(Accepted July 18 2008)

(Online publication September 09 2008)


c1 Corresponding author: Dr James A. Joseph, fax +1 617 556 3222, email


Abbreviations: ALA, α-linolenic acid; LA, linoleic acid; MWM, Morris water maze