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Mediterranean Diet Linked to Reduced Signs of Alzheimer’s Disease

An anatomical model of a brain in cross-section.
Credit: Robina Weermeijer on Unsplash
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A new study has found that people who followed the MIND and Mediterranean diets – rich in foods such as vegetables, whole grains, olive oil and fish – had reduced signs of Alzheimer’s in their brains after death. The research is published in Neurology.

Diet’s effect on cognitive decline

Traditional to many countries along the Mediterranean sea, the Mediterranean diet consists largely of fruits and vegetables, beans, nuts, whole grains, olive oil and fish – in addition to a small amount of red wine.

It has been linked to numerous health benefits, such as reduced risks of developing cardiovascular disease and reductions in overall mortality, in addition to influencing the effects of aging and cognitive function.

Similarly, the MIND diet – which has a lot of features in common with the Mediterranean diet – also shows benefits for cognition. Rich in green leafy vegetables, berries and nuts while avoiding butter, cheese and red meat, the MIND diet was designed to prevent dementia and slow age-related cognitive decline.

Alzheimer’s disease is characterized by the presence of abnormal proteins in the brain, such as plaques of amyloid-beta and tau tangles. To explore the benefits of these diets on Alzheimer’s disease and dementia, researchers from the current study investigated whether following the MIND and Mediterranean diets was associated with a reduction in the presence of plaques and tangles in the brain.

Measuring the biological signs of Alzheimer’s disease

The researchers examined the brain tissue of almost 600 people who participated in the Rush Memory and Aging project and agreed to donate their brains for Alzheimer’s research after their death. On average, the participants passed away seven years after the start of the study, and the researchers examined the brain tissue at autopsy for the presence of amyloid plaques and tau tangles. While typically found in the brains of people with Alzheimer’s disease, they can also be present in the brains of older people with normal cognition. In the study cohort, 39% of participants had been formally diagnosed with dementia prior to their death, while 66% met the criteria for Alzheimer’s disease upon examination after their death.

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The participants also completed yearly questionnaires concerning the different categories of food they consumed and how much. The researchers used this data to rank the participants based on how much they adhered to either the MIND or Mediterranean diet. For example, for the Mediterranean diet, higher scores were given for consumption of cereals, legumes, olive oil and fish, while lower scores were given if they ate red meat or full-fat dairy products. More points for the MIND diet were given for consuming food groups such as nuts, berries and beans while points were lost if they ate foods such as butter, pastries and fried foods more than was recommended.

Those with the highest adherence to the Mediterranean diet were found to have average amyloid plaque and tau tangle levels similar to those 18 years younger than participants with the lowest adherence, even after adjusting for factors such as age, sex, education and the presence of genes associated with Alzheimer’s. Similarly, participants with the highest adherence to the MIND diet had plaque and tangle levels similar to being 12 years younger than the lowest scorers.

The researchers also found that consumption of green leafy vegetables was one of the most important single diet components – those who ate at least seven servings a week had plaque levels similar to being 19 years younger than those who ate one or fewer servings.

“These results are exciting – improvement in people’s diets in just one area – such as eating more than six servings of green leafy vegetables per week, or not eating fried foods – was associated with fewer amyloid plaques in the brain similar to being about four years younger,” said Dr. Puja Agarwal, lead author of the study. “While our research doesn’t prove that a healthy diet resulted in fewer brain deposits of amyloid plaques, also known as an indicator of Alzheimer’s disease, we know there is a relationship and following the MIND and Mediterranean diets may be one way that people can improve their brain health and protect cognition as they age.”

Encouraging findings

Although the findings did reveal an association between adhering to these diets and lower levels of AD pathologies in the brain, further research is required to establish whether this is indeed causation and not correlation. Additionally, these findings cannot be generalized to all populations as the majority of participants were white, non-Hispanic and of an older age.

“Our finding that eating more green leafy vegetables is in itself associated with fewer signs of Alzheimer’s disease in the brain is intriguing enough for people to consider adding more of these vegetables to their diet,” said Agarwal. “Future studies are needed to establish our findings further.”

Reference: Agarwal P, Leurgans SE, Agrawal S, et al. Association of Mediterranean-DASH intervention for neurodegenerative delay and Mediterranean diets with Alzheimer disease pathology. Neurology. 2023. doi: 10.1212/WNL.0000000000207176

This article is a rework of a press release issued by the American Academy of Neurology. Material has been edited for length and content.