Published in Epidemiology, the review is the first systematic analysis research relating to the Mediterranean diet and cognitive functions, and reveals a positive impact on cognitive function, but an inconsistent effect on mild cognitive impairment.
Led by Iliana Lourida from the University of Exeter in the UK, the team analysed 12 eligible pieces of research, 11 observational studies and one randomised control trial. In nine out of the 12 studies, a higher adherence to a Mediterranean diet was associated with better cognitive function, lower rates of cognitive decline and a reduced risk of Alzheimer's disease.
However, results for mild cognitive impairment were inconsistent, said the team.
"Mediterranean food is both delicious and nutritious, and our systematic review shows it may help to protect the ageing brain by reducing the risk of dementia. While the link between adherence to a Mediterranean diet and dementia risk is not new, ours is the first study to systematically analyse all existing evidence," said Lourida.
The review also highlights 'inconsistencies' in the literature and the need for further research, she said - noting, in particular, that "research is needed to clarify the association with mild cognitive impairment and vascular dementia."
"It is also important to note that while observational studies provide suggestive evidence we now need randomised controlled trials to confirm whether or not adherence to a Mediterranean diet protects against dementia," said Lourida.
The research team identified 12 studies (11 observational studies and one randomized controlled trial) that met their inclusion criteria.
"Despite methodological heterogeneity and limited statistical power in some studies, there was a reasonably consistent pattern of associations," said Lourida and her colleagues - noting that a higher adherence to Mediterranean diet was associated with better cognitive function, lower rates of cognitive decline, and reduced risk of Alzheimer disease in nine out of the 12 studies.
"Long-term randomised controlled trials promoting a Mediterranean diet may help establish whether improved adherence helps to prevent or delay the onset of Alzheimer disease and dementia," said the research team.
The research was supported by the National Institute for Health Research Collaboration for Leadership in Applied Health Research and Care in the South West Peninsula (NIHR PenCLAHRC).
Volume 24 - Issue 4 - p 479-489, doi: 10.1097/EDE.0b013e3182944410
"Mediterranean Diet, Cognitive Function, and Dementia: A Systematic Review"
Authors: Lourida, Ilianna; Soni, Maya; Thompson-Coon, Joanna