Study shows no evidence Mediterranean diet helps prevent cognitive decline

The Mediterranean diet, so named due to its roots in Italian, Spanish and Greek culture, is rich in whole grains, fruits, nuts and oily fish, has been the subject of much study in the past few years due to its health benefits. Thus far, it has been shown to be heart healthy and a good plan for people to follow who suffer from adult diabetes. Following such reports, there has been speculation that the diet might also help stave off dementia or even Alzheimer's as people age. The thinking was that because the diet tends to be very low in saturated fats, blood vessels in the brain wouldn't become blocked. In this new effort, the research team suggests that such claims have no merit.

To found out if people who followed the Mediterranean diet gained any cognitive defense against dementia, the researchers studied the eating habits of 3000 middle aged people over a 13 year period. As they turned 65, they were divided into three groups by how strictly they stuck with the diet and were subsequently tested using standard cognitive tests, e.g. how many words could they remember in a list, etc. The researchers report they found no differences in cognitive ability between members of the three groups, which they say shows that eating a Mediterranean diet does not slow or prevent dementia.

Emmanuelle Kesse-Guyo, lead researcher on the project, told the press that the study shows that sticking to a Mediterranean diet, at least from middle age on, won't help in preventing cognitive decline due to aging or disease. She went on to say that other studies have found similar results. Just last year, for example, a team from Foundation for Public Health, also in France, found that in testing women over the age of 65 who claimed to have been strict adherents of the diet, there were no apparent differences in cognitive decline between them and the general population.

More information: Mediterranean diet and cognitive function: a French study, The American Journal of Clinical Nutrition, First published January 2, 2013, doi: 10.3945/​ajcn.112.047993

Abstract
Background: Evidence on the association between Mediterranean diet (MedDiet) adherence and cognition is presently inconsistent.
Objectives: The aims of this study were to investigate the association between midlife MedDiet adherence and cognitive performance assessed 13 y later among participants in the SU.VI.MAX (Supplementation with Vitamins and Mineral Antioxidants) study and to test the hypothesis of effect modification by occupation and education as cognitive reserve markers.
Design: A Mediterranean Diet Score (MDS) and a Mediterranean-Style Dietary Pattern Score (MSDPS) were estimated by using repeated 24-h dietary records (1994–1996) from 3083 middle-aged subjects. Cognitive performance was assessed in 2007–2009 by using 6 neuropsychological tests, and a composite score was built. Subgroup analyses were performed according to occupational and educational status. Mean differences and 95% CIs were estimated through covariance analyses.
Results: After potential confounders were accounted for, no association between MDS or MSDPS and cognitive scores was detected except for a lower phonemic fluency score with decreasing MSDPS (P = 0.048) and a lower backward digit span score with decreasing MDS (P = 0.03). In turn, a low MDS was related to a lower composite cognitive score in the small subsample of manual workers (n = 178, P-interaction = 0.04) who could be hypothesized to have low cognitive reserve. MedDiet adherence did not interact with educational level in relation to cognitive function.
Conclusion: This study did not find support for a beneficial effect of MedDiet adherence on cognitive function, irrespective of educational level, which is the strongest indicator of cognitive reserve. This trial was registered at clinicaltrials.gov as NCT00272428.

Journal reference: American Journal of Clinical Nutrition

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