A study published on March 14, 2023 found that consumption of a Mediterranean Diet reduces a person's risk of developing dementia, independent of genetic risk.
Over 60,000 participants between the ages of 40 and 69 in the UK were followed for an average of 9.1 years. It was found that people who eat a Mediterranean diet are an estimated 23% less likely to develop dementia, including Alzheimer's disease.
“The main take home message from this study is that, even for individuals with a higher genetic risk, consuming a more Mediterranean-like diet could reduce the likelihood of developing dementia,” said the study’s lead author, Oliver Shannon, a lecturer in human nutrition and aging at Newcastle University. 
Participants were scored for adherence to the Mediterranean diet. According to Newcastle's Shannon, to have the perfect Mediterranean diet score, weekly consumption should include:
- Olive oil as the main cooking fat.
- 2 or more servings of vegetables per day.
- 3 or more servings of fruit per day.
- Less than 1 serving of red/processed meat per day.
- Less than 1 serving of butter, margarine or cream per day.
- Less than 1 sugar-sweetened drink per day.
- 3 or more servings of legumes, such as beans, lentils or peanuts, per week.
- 3 or more servings of fish per week.
- Less than 2 servings of sweets or pastries per week.
- 3 or more servings of nuts per week.
- More white meat than red meat in the diet.
- 2 or more servings of a tomato-based sauce per week.
The new research adds to the mounting evidence that the Mediterranean diet can impact the risk of dementia even in people who are at a higher risk because of their genes, said Dr. Thomas Wisniewski, a professor of neurology, pathology and psychiatry and director of the Alzheimer’s Disease Research Center and the Center for Cognitive Neurology at NYU Langone. “This study with really good numbers and a fairly substantial effect size is showing that, indeed, it is brain protective to follow a Mediterranean diet," Wisniewski said (emphasis added). “It’s positive news and certainly something that everyone can do relatively easily. So it’s good news.”
Olive Oil Is Not Just for Prevention
Earlier this month, Auburn University’s Harrison College of Pharmacy published a study in the journal “Nutrients,” showing that both regular olive oil and extra virgin olive oil may have positive effects on individuals who already suffer from dementia. The team studied 25 participants experiencing mild cognitive impairment for 6 months. Half of the participants consumed three tablespoons of olive oil per day for six months, the other half consumed the same amount of extra virgin olive oil.
Cognitive tests, blood tests, and MRI scans were used to find that both olive oil and extra virgin olive oil improved cognitive function. The blood tests show that both olive oil and extra virgin olive oil positively impact the processing and clearance of beta-amyloid, which is implicated in Alzheimer's disease.
Interestingly, the findings suggest that at least part of the cognitive benefits from consuming olive oil can be attributed to oleic acid, which is prevalent in both grades of olive oil.
MRI scans shows that extra virgin olive oil had the added benefit of enhancing the blood-brain barrier function and the functional connectivity between different brain areas.“These results are exciting because they support the health benefits of olive oil against Alzheimer’s disease,” said lead researcher Amal Kaddoumi. “Based on the findings of this study and previous pre-clinical studies by us and others, we can conclude that adding olive oil to our diet could maintain a healthy brain and improve memory function.”  Mediterranean diet adherence is associated with lower dementia risk, independent of genetic predisposition: findings from the UK Biobank prospective cohort study Mediterranean diet may reduce risk of dementia or Alzheimer's, research shows A diet rich in vegetables, nuts, whole grains and fish reduced the likelihood of developing  Extra-Virgin Olive Oil Enhances the Blood–Brain Barrier Function in Mild Cognitive Impairment: A Randomized Controlled Trial  Auburn researcher finds olive oil to improve brain health, memory in mild cognitive impairment individuals