Walnuts may help to slow cognitive decline in at-risk older adults, according to a study of elderly participants in California and Spain.

Researchers followed two groups. One ate a diet supplemented with walnuts and the other abstained from consuming them for two years. Repeat cognitive testing and brain scans showed no notable cognitive changes in healthy participants. But walnut consumption appeared to have minor effects on cognition among participants who smoked more and had relatively low neuropsychological test scores at the study’s start, said Joan Sabaté, M.D., Ph.D., from Loma Linda University School of Public Health, California.

Walnuts contain omega-3 fatty acids and polyphenols, which have been found to counteract the oxidative stress and inflammation which drive cognitive decline.

While the results were inconclusive, they suggest that walnut consumption might delay cognitive impairment over longer periods of time, concluded Sabaté, a professor of nutrition and epidemiology. In previous research, he and his colleagues found that walnut consumption helps to lower blood cholesterol. 

The study was published in the American Journal of Clinical Nutrition.