Kitchen & Garden, Uncategorized

Is the Mediterranean Diet protective for the ageing brain?

The Mediterranean diet has been widely investigated in relation to its benefits on multiple conditions. It has been shown to lower inflammation and reduce the risk of mortality from cardiovascular disease and cancer.[1]

It emphasises eating primarily a plant-based diet, with high consumption of fruit, vegetables, legumes, cereals, olive oil (as the primary source of fat), moderate consumption of fish, low to moderate intake of dairy and wine, and a low intake of red meat and poultry.

More recently, the scientific community has investigated the Mediterranean diet (MeDi) and its role in protecting the ageing brain. A study, comprising more than 400 individuals aged 73-76 from Scotland, found that those who were low consumers of the MeDi had significantly lower total brain volume over a 3-year period than those who regularly adhered to this type of diet.[2]

The longitudinal study focused on measurements of brain volumes (total and grey matter) and cortical thickness. Dietary data was collected at baseline and willing participants underwent MRI brain scans at ages 73 and 76. Individuals lived independently and were free from dementia at baseline.

Based on the data they provided, each patient was given an MeDi score between 0 and 9. Beneficial food components (fruit, vegetables, legumes, fish and cereal) were valued with 1 point each, while detrimental components (dairy and meat) were scored as 0. Higher scores (5-9) indicated greater MeDi adherence.

The results of the trial showed that greater adherence to the MeDi was more protective against total brain atrophy. This group showed greater grey matter volume (GMV) and total brain volume (TBV) at age 73 and greater GMV and mean cortical thickness at age 76.

Interestingly, the beneficial effects of MeDi were significant even when controlling for education and IQ. This suggests that the effects of the diet are not simply a result of healthier lifestyle choices in more educated or intelligent individuals (who tend to have larger brain volumes).[2]

In opposition to what has been demonstrated in previous studies, fish and meat consumption were not found to drive the changes in this study. Hence, it could be assumed that other components of the diet, or a combination of components within the diet, are responsible for the improvements seen.

However, results from the Women’s Health Study found that higher monosaturated-to-saturated fat ratios have been associated with favourable cognitive function trends over time. In this same study, the authors discovered a modest association between a higher wholegrain intake and better average cognition scores.[3]

Previous studies conducted on cognitive function in elderly people suggest that measurements of brain injury and atrophy contribute to cognitive decline.[4] An increase in cerebral amyloid-beta (Aβ) levels is also associated with brain volume loss and longitudinal cognitive decline, including reduction in episodic memory, working memory and visuospatial ability.[5]In comparison to this, the larger the total brain volume, the larger the amount of grey matter.[6]

The MeDi has been extensively studied in relation to a number of morbidities. Interestingly, it is suspected to play a role in mood support as a loss of brain volume and grey matter reduction has been correlated to more severe symptoms in elderly individuals with depressive disorders.[7]

An Australian study, known as the SMILES trial, displays preliminary randomised, controlled trial evidence that MeDi-style dietary improvement may be an efficacious treatment strategy for treating major depressive episodes, resulting in significant reductions in depression symptoms.[8]

These results are in agreement with previous investigations, demonstrating associations between subthreshold depressive symptoms and smaller prefrontal brain volumes. It also parallels evidence that shows the impact of depression on cognitive function worsens with age.[9]

Protection of total brain volume and grey matter volume is key to protecting the ageing brain, preventing cognitive decline and reducing the risk of severe depressive symptoms. Evidence is showing that following the Mediterranean diet is a strategy that can be employed to do this. The far-reaching effects of the diet to reduce the risk of cardiovascular disease, reduce inflammation and protect the ageing brain reinforces that clinicians should strongly consider implementing this diet in an elderly population.

This article first appeared on FX Medicine.

References:

  1. Aridi YS, Walker JL, Wright OR. The association between the Mediterranean dietary pattern and cognitive health: a systematic review. Nutrients 2017;9(7):674 [Full Text]
  2. Luciano M, Corley J, Cox SR, et al. Mediterranean-type diet and brain structural change from 73 to 76 years in a Scottish cohort. Neurology 2017;88(5):449-455. [Full Text]
  3. Samieri C, Grodstein F, Rosner BA, et al. Mediterranean diet and cognitive function in older age: results from the Women’s Health Study. Epidemiology 2013;24(4):490-499. [Full Text]
  4. Farias S, Mungas D, Reed BR, et al. Maximal brain size remains an important predictor of cognition in old age, independent of current brain pathology. Neurobiol Aging 2012;33(8):1758–1768. [Full Text]
  5. Storandt M, Mintun MA, Head D, et al. Cognitive decline and brain volume loss are signatures of cerebral Aβ deposition identified with PIB. Arch Neurol 2009;66(12):1476-1481. [Full Text]
  6. Hofman MA. Evolution of the human brain: when bigger is better. Front Neuroanat 2014;8:15. [Full Text]
  7. Geerlings MI, Brickman AM, Schupf N, et al. Depressive symptoms, antidepressant use, and brain volumes on MRI in a population-based cohort of old persons without dementia. Alzheimers Dis 2012;30(1):75-82. [Full Text]
  8. Dotson VM, Davatzikos C, Kraut MA, et al. Depressive symptoms and brain volumes in older adults: a longitudinal magnetic resonance imaging study. J Psychiatry Neurosci 2009;34(5):367-375. [Full Text]
  9. Jacka FN, O’Neil A, Opie R, et al. A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial). BMC Med 2017;15:23. [Full Text]

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