David B. Reuben, MD

Disclosures

September 30, 2016

Editorial Collaboration

Medscape &

Question

Can a good diet prevent dementia?

Response from David B. Reuben, MD
Professor and Archstone Foundation Endowed Chair, Department of Medicine, University of California, Los Angeles; Chief, Division of Geriatrics, UCLA Medical Center, Santa Monica, California

Dietary interventions to prevent dementia or cognitive decline are generally safe, readily available, and can be easier to implement than interventions such as exercise. But evidence supporting these interventions varies. Perhaps the best studied is the Mediterranean diet, which is high in grains, vegetables, fruit, potatoes, nuts, seeds, legumes, fish, and olive oil, and low in red meat, poultry, dairy, and alcohol. The dietary approach to stop hypertension (DASH) diet is similar, but is higher in low-fat dairy and lower in fish. The Mediterranean–DASH intervention for neurodegenerative delay (MIND) diet incorporates elements of both these diets but places more emphasis on berries, nuts, and beans.

A meta-analysis of prospective cohort studies showed that people who adhere to a Mediterranean diet have lower rates of Alzheimer disease and Parkinson disease.[1] Similarly, studies of community-dwelling older people who followed the MIND diet showed less decline in global episodic, semantic, and working memory and in perceptual speed and perceptual organization at 4.7-year follow-up.[2] In addition, these study participants were less likely to have developed Alzheimer disease at 4.5-year follow-up.[3]

Data from some randomized clinical trials support the use of these diets to prevent cognitive decline and dementia. In the PREDIMED study, participants 55-80 years of age at high risk for cardiovascular disease were randomly assigned to one of three diets: a Mediterranean diet with supplemental extra-virgin olive oil, a Mediterranean diet with supplemental mixed nuts, or a regular diet that emphasized reduced dietary fat. There was a reduction in the composite of myocardial infarction, stroke, and death from cardiovascular causes—the primary endpoint—with the supplemented Mediterranean diets.[4] A secondary analysis demonstrated higher scores on the Mini-Mental State Examination and the clock-drawing test at 6.5 years.[5] In a short-term study, participants randomized to a DASH diet had better psychomotor speed at 4-month follow-up.[6]

 
This body of evidence is suggestive of, but not conclusive for, the benefit of a healthy diet on cognition and dementia.
 

Diet can also be effective when it is part of a multicomponent intervention. In the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER),[7] 1260 participants with cardiovascular risk factors for dementia and cognitive performance at the mean or slightly lower than expected for age were randomly assigned to a multicomponent intervention (diet, exercise, cognitive training, and vascular risk monitoring) or to health advice (control group).The dietary component included fruit and vegetables, whole-grain cereal products, low-fat milk and meat products, low sugar, margarine instead of butter, and at least two portions of fish per week. The primary outcome measure was change in performance on a neuropsychological test battery (NTB) of 14 tests. During the 24-month follow-up period, the NTB composite score was 25% higher in the intervention group than in the control group, and executive functioning and processing speed were better in the intervention group. However, memory was no better in the intervention group than in the control group.

This body of evidence is suggestive of, but not conclusive for, the benefit of a healthy diet on cognition and dementia. Coupled with other benefits related to hypertension and cardiovascular disease,[4,8] clinicians should consider recommending these diets for appropriate older people.

Developed in association with the UCLA Alzheimer's and Dementia Care Program.

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