Mediterranean diet improves cognition: the PREDIMED-NAVARRA randomised trial.

Martínez-Lapiscina EH, Clavero P, Toledo E, et al.
J Neurol Neurosurg Psychiatry. 2013 May 13

Background

The potential protective effect of nutrients such as fatty acids, vitamins, fish, fruit and vegetables on cognition has been studied, but results are inconsistent [1].The Mediterranean diet (MedDiet) is characterised by the consumption of olive oil as the main culinary fat and high intake of plant-based foods (fruits and nuts, vegetables, legumes and minimally processed cereals). Also, moderate-to-high consumption of fish and seafood and low consumption of butter or other dairy products and meat or meat products is typical. Regular, but moderate intake of alcohol, often red wine during meals, is common [2].
Previous observational studies have examined the relationship between cognition and following the MedDiet, but results were not always consistent. This study therefore evaluated global cognition among participants in a long-term prevention randomised trial that compared two interventions with MedDiet versus a low-fat diet. The PREDIMED (PREvención con DIeta MEDiterránea) study assigned subjects randomly to a MedDiet supplemented with extra virgin olive oil (EVOO) or mixed nuts, or to a low-fat diet usually recommended for the primary prevention of cardiovascular disease (CVD)[3]. The stopping boundary for the benefit of the MedDiet on the primary end point of myocardial infarction, stroke or cardiovascular death was met after over 6 years of study duration [4].
This subanalysis included 522 older (55-80 years old) subjects at high vascular risk but initially free of CVD, who underwent a neuropsychological testing (Mini-mental state examination: MMSE and Clock drawing test: CDT) after a mean 6.5 years of follow-up.

Main results

• Mean adjusted differences in MMSE and CDT scores were statistically significantly positive when comparing the MedDiet+EVOO group to the control group (MMSE: +0.62, 95%CI:0.18-1.05, P=0.005, CDT: +0.51, 95%CI: 0.20-0.82, P=0.001), as well as the MedDiet+nuts group to the control group (MMSE: +0.57, 95%CI:0.11-1.03, P=0.0015, CDT: +0.33, 95%CI: 0.003 – 0.67, P=0.048)(multivariate regression analyses).
• The presence of the ApoE4 genotype, female sex, and older age were all significantly and independently associated with a lower MMSE and CDT score, while more years of education predicted better scores.
• After 6.5 years of nutritional intervention, 18 individuals in the MedDiet+EVOO group had incident mild cognitive impairment, 19 in MedDiet+nuts and 23 in the low-fat diet group. There were 12 cases of incident dementia in the MedDiet+EVOO group, 6 in MedDiet+nuts and 17 in the control group.

Conclusion

This study suggests that nutritional intervention with a Mediterranean diet supplemented with either EVOO or nuts is associated with improved global cognition, as compared to a control low-fat diet, independently of potential confounders. Although no baseline cognitive assessment was performed, these findings support the protective effect of a Mediterranean diet on cognitive function.

References

1. Coley N, Andrieu S, Gardette V, et al. Dementia prevention: methodological explanations for inconsistent results. Epidemiol Rev 2008;30:35–66.
2.  Willett WC, Sacks F, Trichopoulou A, et al. Mediterranean diet pyramid: a cultural model for healthy eating. Am J Clin Nutr 1995;61:1402S–06S.
3. Martínez-González MÁ, Corella D, Salas-Salvadó J, et al. Cohort profile: design and methods of the PREDIMED study. Int J Epidemiol 2012;41:377–85.
4. Estruch R, Ros E, Salas-Salvadó J, et al. Primary prevention of cardiovascular disease with a mediterranean diet. N Engl J Med 2013;368:1279–90.

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