REVIEW OF: Tessier AJ et al, JAMA Netw Open 2024;7(5):e2410021

STUDY TYPE: Prospective observational cohort study

Dementia deaths are increasing in the US, even as rates from other chronic diseases decline. Could olive oil, a cornerstone of the Mediterranean diet, offer some protection? Researchers examined long-term diet data from nearly 92,000 US participants in the Nurses’ Health Study and Health Professionals Follow-Up Study, all of whom were free of heart disease and cancer at baseline. Starting in 1990, participants completed food questionnaires every four years and were followed for 28 years for dementia-related deaths.

People who consumed more than 7 g/day of olive oil (about half a tablespoon) had a 28% lower risk of dementia death compared to those who rarely or never consumed it. The benefit held regardless of genetic risk (APOE ε4 status) or overall diet quality.

To go further, the researchers used statistical “substitution models” to ask what would happen if people replaced other fats with olive oil. These analyses suggested that replacing 5 g/day of margarine or mayonnaise with olive oil was linked to an 8%–14% lower dementia death risk. Replacing butter or other vegetable oils showed no difference. The protective effect appeared stronger in women than men.

Carlat Take
This study shows an association between higher olive oil use and lower dementia-related mortality, meaning fewer deaths with dementia listed as a cause, not evidence that olive oil prevents dementia. Still, the findings add to the case for olive oil as a safe, heart-healthy fat that may also reduce the risk of dying from dementia-related complications. For patients looking for diet changes that could support long-term brain health, suggesting olive oil as a substitute for margarine or mayonnaise is a reasonable, low-risk step—especially as part of a broader healthy eating pattern.