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Food for Thought: The Role of Walnuts in Cognitive Function and Healthy Aging

Saturday, April 8, 2017  
Posted by: Emily Eastin
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Quality of life and the ability to maintain independence are key factors to healthy aging that most people strive to preserve as they grow older. Research shows that consuming specific foods, like walnuts, may play a role in helping to maintain and improve both physical and cognitive health. 

Nutrients found in walnuts, such as polyphenols, tocopherols and polyunsaturated fatty acids, may reduce oxidative stress and inflammation as well as help maintain neural membrane integrity and reduce protein aggregation involved in Alzheimer’s disease.1 In terms of heart health, more than 25 years of investigation has shown that including walnuts in the diet has beneficial effects which may decrease risk for neurodegenerative diseases and age-related cognitive decline. 

Research continues to evolve, but people of all ages can benefit from taking steps, including healthy diet changes, to maintain health and well-being throughout the aging process. Below is a summary of new publications supported by the California Walnut Commission.

  • Walnuts and Cognitive Function: Eating walnuts may improve performance on cognitive function tests, including those for memory, concentration, and information processing speed in adults (ages 20-59 and 60 and older). 2 This retrospective study was the first large representative analysis of walnut intake and cognitive function, and the only study to include all available cognitive data across multiple National Health and Nutrition Examination (NHANES) surveys, representing over 10,000 individuals. Cognitive function was consistently greater in adult participants that consumed walnuts, regardless of age, gender, race, education, BMI, smoking, alcohol consumption and physical activity.
  • A Mediterranean Diet May Help Counter Cognitive Decline: Eating a Mediterranean diet supplemented with extra virgin olive oil or nuts (primarily walnuts) may counter age-related decline in cognitive function in an older population (ages 55-80).3 This clinical trial was conducted in a subcohort of the PREvención con DIeta MEDiterránea (PREDIMED) trial and included 447 Spanish participants at high cardiovascular risk. Researchers found that participants who consumed a nut mixture containing 15 grams of walnuts, 7.5 grams of hazelnuts and 7.5 grams of almonds, showed improvements in memory compared to a control diet. Though it’s difficult to precisely define what part of the diet was associated with these benefits, the findings support a Mediterranean-style diet for improved cognitive health. 
  • Walnuts and Physical Function: Research has found that eating one to two servings of walnuts per week (1 ounce per serving) was associated with reduced risk of developing impairments in physical function in older women, which may help to maintain independence throughout the aging process.4 Researchers looked at data from 54,762 women in the prospective Nurses’ Health Study, which tracked women for more than 30 years. The findings emphasized that overall diet quality, rather than individual foods, may have a greater impact on reducing risk of physical function impairments. Specifically, diet quality traits most associated with reduced rates of incident physical impairment were higher intake of fruits and vegetables; lower intake of sugar-sweetened beverages, trans fat, and sodium; and moderate alcohol intake. Among food components, the strongest relations were for increased intake of walnuts, oranges, orange juice, apples, pears and romaine or leaf lettuce.
  • Walnuts and the Fight Against Alzheimer’s Disease: An animal study found that a diet including walnuts may have a beneficial effect in reducing the risk, delaying the onset, slowing the progression of, or preventing Alzheimer’s disease.5 This research examined the effects of dietary supplementation with six or nine percent walnuts (equivalent to 1 and 1.5 ounces of walnuts per day in humans) in mouse models of Alzheimer’s disease, compared to a control diet with no walnuts. The study found significant improvement in learning skills, memory, reducing anxiety, and motor development in mice fed a walnut-enriched diet.

As with any research, there are limitations that should be considered. Animal studies are provided as background and used to formulate hypotheses for additional research needed to determine the effects on humans. Residual confounding cannot be ruled out (i.e., other lifestyle habits which are more common in adults who eat walnuts could contribute to the study results) and findings cannot prove causality in observational studies. More research is also needed to clarify how the health benefits apply to other populations. 

For additional health research information, check out the California Walnut Commission’s Nutrition & Scientific Research Guide, a collection of scientific summaries on a variety of topics, including omega-3s, heart health, healthy aging, cancer, weight, the Mediterranean diet and male reproductive health, or the health research database, which includes hundreds of published abstracts. 

1. Poulose SM, Miller MG, Shukitt-Hale B. Role of walnuts in maintaining brain health with age. J Nutr. 2014;144(4 Suppl):561S-566S.
2. Arab L, Ang A. A cross sectional study of the association between walnut consumption and cognitive function among adult us populations represented in NHANES. J Nutr Health Aging. 2015;19(3):284-90.
3. Valls-Pedret C, Sala-Vila A, Serra-Mir M, et al. Mediterranean diet and age-related cognitive decline: a randomized clinical trial. JAMA Intern Med. 2015;175(7)1094-103. 
4. Hagan KA, Chiuve SE, Stampfer MJ, et al. Greater adherence to the alternative healthy eating index is associated with lower incidence of physical function impairment in the nurses’ health study. J Nutr. 2016;146(7):1341-47.  
5. Muthaiyah B, Essa MM, Lee M, et al. Dietary supplementation of walnuts improves memory deficits and learning skills in transgenic mouse model of Alzheimer's disease. J Alzheimers Dis. 2014;42(4):1397-405. 

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