Eating about 7 grams of olive oil a day — roughly one teaspoon — was linked with a 28 percent lower risk of dying from dementia, a Harvard research team found.
The long-term study found that people who regularly used olive oil were better protected against cognitive decline and tended to live longer.
Lead author Anne-Julie Tessier, a nutrition researcher at Harvard, said swapping fats like margarine and commercial mayonnaise for olive oil may lower the risk of fatal dementia.
How the Study Was Conducted
Over 28 years, the researchers followed more than 92,000 adults.
At the start, the average participant was 56. The pool included about 60,600 women and nearly 32,000 men from the Health Professionals Follow-Up Study.
Every four years, participants completed diet questionnaires and the Alternate Healthy Eating Index, which ranks foods and nutrients by their links to chronic disease risk. A higher score indicates a healthier diet, CNN reported.
Participants who consumed about a teaspoon of olive oil daily had a 28 percent lower risk of dying from dementia than those who rarely or never used it.
The team also found that replacing just one teaspoon of margarine or mayonnaise with olive oil was associated with an 8–14 percent lower risk of dementia death. Replacing margarine or mayonnaise with other oils or butter did not show the same benefit.
Some participants carried the APOE e4 gene, the strongest known genetic risk factor for Alzheimer’s disease. Carriers were five to nine times more likely to die from dementia than noncarriers, yet the apparent benefits of olive oil held true for them, too.
The findings were published in JAMA Network Open.
What Scientists Are Saying
Although overall diet quality didn’t change the main finding, people who used olive oil probably had healthier lifestyles overall.
Tessier said the benefits may come from antioxidant compounds in olive oil that can cross the blood-brain barrier and act directly on the brain.
It’s also possible that olive oil has an indirect effect on brain health by improving cardiovascular health, she said.
David Curtis, an honorary professor at University College London, added that roughly half of dementia cases are caused by vascular disease, and anything that improves cardiovascular health — like quitting smoking — can lower dementia risk.
Earlier studies have shown olive oil benefits heart, brain, and bone health. Use it to make salad dressings, mayonnaise, pesto, or dipping sauces for bread.
Dwayne Mellor, a nutrition expert at Aston University in the U.K., pointed out that food’s impact on brain function depends not just on what we eat but also on how we eat.
He added that eating with good company can benefit mental health in the short term and help preserve cognitive function as we age.
