Healthy Aging

What the Research Says

Nutrients in walnuts, including polyphenols, tocopherols and polyunsaturated fatty acids, may be contributing factors in protecting against the detrimental effects of aging.1,2 Epidemiological research suggests walnut consumption may be associated with improved cognitive function. Findings from animal studies have also shown a correlation between a walnut-enriched diet and improved motor and cognitive behavior in aged animals. Additionally, studies have shown that the inclusion of walnuts in the diet may improve cardiovascular health, which is a risk factor for neurodegenerative diseases and age-related cognitive decline.

Scientific evidence suggests that including walnuts as part of a healthy diet may play a role in helping to maintain and improve physical and cognitive health as people age. Below is an overview of the scientific research.

Research Information

According to a epidemiological study published in The Journal of Nutrition, Health & Aging, 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).3 In this retrospective study, cognitive function was consistently greater in adult participants who consumed walnuts, even after adjusting for age, gender, race, education, BMI, smoking, alcohol consumption and physical activity. Analyses are based on single, 24-hour recalls, which reflect one day of intake for the subjects. This cross-sectional 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.

study published in the Journal of the American Medical Association Internal Medicine found that eating a Mediterranean diet supplemented with olive oil or nuts (primarily walnuts) was correlated with reduced age-related decline in cognitive function in an older Spanish population (ages 55-80) at high cardiovascular risk.4 This clinical trial was conducted in a subcohort of the PREvención con DIeta MEDiterránea (PREDIMED) trial. Participants (447 total) were randomly assigned to a Mediterranean diet supplemented with mixed nuts (15g walnuts, or about 0.5 ounces, 7.5g almonds and 7.5g hazelnuts per day), a Mediterranean diet supplemented with extra virgin olive oil (at least 50g or 4 tablespoons per day) or a low-fat diet (control group). The study found that participants who consumed a Mediterranean diet with nuts, including walnuts, showed improvements in memory compared to a low-fat diet.

An animal study published in the Journal of Alzheimer’s Disease demonstrated that a diet including walnuts may have a beneficial effect in reducing the risk, delaying the onset, or slowing the progression of Alzheimer’s disease.5 The research group examined the effects of dietary supplementation with 6 percent or 9 percent walnuts in mice (equivalent to 1 ounce and 1.5 ounces of walnuts per day in humans) compared to a control diet with no walnuts. The study found significant improvement in learning skills, memory, anxiety reduction, and motor development in mice fed a walnut-enriched diet. This research stemmed from a previous cell culture study that highlighted the protective effects of walnut extract against the oxidative damage caused by amyloid beta protein, the major component of amyloid plaques that form in the brains of those with Alzheimer’s disease.6 Findings from animal and cell studies are provided as background and used to formulate hypotheses for additional research needed to determine the effects on humans.

An epidemiological study published in Nutrients demonstrated that consuming walnuts may be associated with reduced depression symptoms among American adults.7 Researchers examined data on 26,656 American adults (ages 0-85 years) from the National Health and Nutrition Examination Survey (NHANES). Those who ate walnuts were more likely to have greater interest in activities, higher energy levels, less hopelessness (for women) better concentration, and greater optimism, compared to those who did not consume nuts. These results held even after controlling for age, sex, race, income, BMI, smoking, alcohol consumption, and marital status. On average, walnut consumers ate about 24 grams of walnuts per day (just shy of a one-quarter cup serving). While the association between nut consumption and lower depression symptoms was consistent for men and women, the effect appeared to be strongest among women, who are more likely to report greater depression symptoms and use of antidepressants, compared to men.

study published in Nutrients found that walnut consumption may help improve mood in men.8 While maintaining their typical diet, activities and lifestyle habits, participants (college-age men and women) consumed half a cup of walnuts daily for eight weeks. Mood was assessed using a common questionnaire (Profiles of Mood States (POMS)) about key domains such as tension, depression, anger, vigor, fatigue and confusion. The findings showed that non-depressed healthy, young males (ages 18-25) had a 27% reduction in overall mood disturbances. No significant changes in mood were observed in females or when the data was analyzed with both genders included.

Physical Function

Research published in the Journal of Nutrition, Health and Aging and Journal of Nutrition demonstrated that eating a healthy diet, that includes foods like walnuts, was associated with reduced likelihood of developing physical impairment in older adults. This is an important factor that can help to maintain independence throughout the aging process.9,10 Researchers examined data from 12,658 men from the Health Professionals Follow-Up Study over four years, and 54,762 women in the prospective Nurses’ Health Study. Better diet quality, which included consuming foods like walnuts, was strongly associated with reduced risk of developing of physical impairment. An overall healthy diet pattern was more strongly associated with better physical function than an individual component or food, but greater intake of vegetables and nuts, and lower intake of red or processed meats and sugar-sweetened beverages each modestly lowered risk of impairment.

For epidemiological studies, 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. 3,4,7,9,10 More research is also needed to clarify how the health benefits apply to other populations, as well as to determine the optimal quantity of walnuts needed to confer associated benefits. 3,4,7,8,9,10 In the context of a Mediterranean diet, it is difficult to precisely define what part of the diet is associated with cognitive health.4 Additionally, dietary choices over the course of one to two days may not be representative of usual consumption patterns, and data obtained by self-report may have some flaws.3,7,9,10 Depression may also change typical appetite and eating behaviors.7

Loose California Walnuts

Healthy Aging Research

View peer-reviewed publications supported by the California Walnut Commission.

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1 Walnuts offer a variety of antioxidants (3.721 mmol/oz), including polyphenols (69.3 ± 16.5 μmol catechin equivalents/g) and gamma tocopherol (5.91 mg/ounce). The data for antioxidant capacity of foods generated by test-tube methods cannot be extrapolated to human effects.  Clinical trials to test benefits of dietary antioxidants have produced mixed results. One ounce of walnuts provides 18g of total fat, 2.5g of monounsaturated fat, 13g of polyunsaturated fat, including 2.5g of alpha-linolenic acid, the plant-based omega-3.

2 Poulose SM, Miller MG, Shukitt-Hale B. Role of walnuts in maintaining brain health with age. J Nutr. 2014;144(4 Suppl):561S-566S.

3 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.

4 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.

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.

6 Chauhan N, Wang KC, Wegiel J, et al. Walnut extract inhibits the fibrillization of amyloid beta-protein, and also defibrillizes its preformed fibrils. Curr Alzheimer Res. 2004;1(3):183-8.

7 Arab L, Guo R, Elashoff D. Lower Depression Scores among Walnut Consumers in NHANES. Nutrients. 2019;11(2):275.

8 Pribis P. Effects of Walnut Consumption on Mood in Young Adults – A Randomized Controlled Trial. Nutrients. 2016;8(11):668.

9 Hagan KA, Grodstein F. The Alternative Healthy Eating Index and Physical Function Impairment in Men. J Nutr Health Aging. 2019;23(5):459-65.

10 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.

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