Mediterranean staple may lower your risk of death from dementia, study finds

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A daily spoonful of olive oil could lower your risk of dying from dementia, according to a new study by Harvard scientists.

For more than 92,000 adults observed over 28 years, consuming at least 7 grams — a bit over half a tablespoon — of olive oil daily was linked with a 28% lower risk of dementia-related death, compared with those who never or rarely ate olive oil, found the study published Monday in the journal JAMA Network Open.

Olive oil can be a healthy, tasty addition to foods such as sandwiches and salads. – knape/E+/Getty Images/File

The study is the peer-reviewed and finalized version of an abstract — early research the authors presented in July 2023 at the American Society for Nutrition’s annual meeting. To the authors’ knowledge, it was also the first to investigate whether the Mediterranean diet staple is linked with risk of death from the disease.

“Our study reinforces dietary guidelines recommending vegetable oils such as olive oil and suggests that these recommendations not only support heart health but potentially brain health, as well,” study coauthor Anne-Julie Tessier, a research associate in nutrition at Harvard University’s T.H. Chan School of Public Health, in a news release for the abstract last year. “Opting for olive oil, a natural product, instead of fats such as margarine and commercial mayonnaise, is a safe choice and may reduce the risk of fatal dementia.”

At the beginning of the study, research participants were age 56 on average. The pool included nearly 60,600 women who had participated in the Nurses’ Health Study from 1990 to 2018, and nearly 32,000 men who had been in the Health Professionals’ Follow-Up Study during the same period. The former study investigated risk factors for major chronic diseases among women in North America, while the latter is looking into the same topics but for men.

The authors of the latest study assessed participants’ diets every four years via a questionnaire and the Alternative Healthy Eating Index, which assigns ratings to foods and nutrients predictive of chronic disease. The higher someone scores on this index, the better.

Replacing 5 grams — around 1.2 teaspoons — of margarine or mayonnaise consumed daily with olive oil was associated with an 8% to 14% lower risk of death from dementia. The results of substituting with other vegetable oils or butter weren’t significant, the authors found.

Participants with the APOE e4 gene — the strongest known genetic risk factor for Alzheimer’s disease — were five to nine times more likely than noncarriers to die from dementia, but the findings regarding olive oil still stood after the authors took this factor into account.

Duane Mellor, a registered dietitian who wasn’t involved in the study, noted in July that the research doesn’t prove a causal relationship, but rather an association.

“More research is needed,” Mellor, the Aston Medical School lead for nutrition and evidence-based medicine at Aston University in the United Kingdom, said in a news release.

Lowering dementia risk

The potential benefits of olive oil for brain health could be due to antioxidant compounds that can cross the blood-brain barrier, directly affecting the brain, Tessier said.

“It is also possible that olive oil has an indirect effect on brain health by benefiting cardiovascular health,” she added.

Though participants’ overall diet quality didn’t make a difference in the findings, those who consume olive oil may have overall healthier lifestyles.

“There are many, many differences between people who consume olive oil and those who do not, and it is never possible to fully account for all possible confounding factors,” said David Curtis, an honorary professor of genetics, evolution and environment at University College London, said in a July news release.

Additionally, the way the Mediterranean diet was scored — as part of the dietary quality assessment — had “only” nine points and is based on the average intake of the population, Mellor told CNN in a May interview.

“It might be more accurate to use an assessment of diet which looks at a wider number of foods, as more than (nine) things make up a healthy diet,” Mellor added.

Another important point to keep in mind is that about half of dementia cases are caused by vascular disease, Curtis added.

“Anything which improved cardiovascular health, such as not smoking, would be expected to reduce dementia risk,” he said. “It has been shown that olive oil consumption is associated with better cardiovascular health, so one would expect that it would also be associated with lower dementia risk.”

Olive oil has been found to be helpful for health of the heart, brain, bones and more. Besides cooking with olive oil, you can also use it to make salad dressings or vinaigrettes, mayonnaise, pesto or bread dip. People should also remember that when it comes to food and brain function, it’s not just about what we eat, but how we eat, Mellor said.

“Remaining sociable around mealtimes and eating with others can benefit our mental health in the short term and cognitive function as we age,” Mellor added.

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