A large prospective cohort study found that older adults who consumed more virgin olive oil, a key component of the Mediterranean diet, had slower cognitive decline and more diverse gut microbiota over two years of follow-up. In contrast, we found that the higher the intake of common refined olive oil, the lower the microbial diversity and the faster it declines.

Virgin olive oil is a cornerstone of the Mediterranean diet and is rich in phenolic compounds with anti-inflammatory and antioxidant properties.

Although previous laboratory and animal studies have suggested neuroprotective effects, human evidence linking olive oil, gut microbiota, and cognition is limited.

This new finding is based on participants in the PREvención con DIeta MEDiterránea-Plus (PREDIMED-Plus) study, an ongoing large-scale trial designed to investigate how diet and lifestyle changes affect cardiovascular and metabolic health.

“This is the first prospective study in humans that specifically analyzes the role of olive oil in the interaction between the gut microbiota and cognitive function,” said Dr. Giaki Ni, a researcher at Rovira i Virgili University.

Researchers followed more than 650 adults aged 55 to 75 who were overweight or obese and at high risk for cognitive decline, but who were cognitively healthy at the start of the study.

Over a two-year period, they tracked participants’ olive oil intake, gut microbiome profiles, and performance on a comprehensive battery of cognitive tests.

Increased intake of virgin olive oil was associated with improved or maintained overall cognition, executive function, and language skills.

In contrast, high intakes of common, mainly refined olive oil were found to reduce microbial diversity in the gut and accelerate cognitive decline.

“At a time when cognitive decline and cases of dementia are on the rise, our findings drive home the importance of improving diet quality and, in particular, prioritizing extra virgin olive oil over other refined olive oils as an effective, simple and accessible strategy to protect brain health,” said researchers Nancy Babio and Stéphanie Nisi from Rovira i Virgili University.

To find out why virgin olive oil may have beneficial effects on cognitive function, scientists analyzed stool samples taken at baseline.

People who consumed more virgin olive oil had more diverse gut microbiota and a clearer microbial community structure than those who consumed less.

Further analysis suggested that specific gut bacteria may help explain the cognitive benefits.

Changes in the abundance of specific microbial species. adlerkreuziaappeared to statistically mediate the association between virgin olive oil intake and improved general cognitive performance, supporting the idea that diet can influence brain health through the gut-brain axis.

“This study supports the idea that the quality of the fats we consume is as important as the quantity,” said Dr. Jordi Salas Salvado, also from Rovira y Virgili University.

“Extra virgin olive oil not only protects your heart, but also helps protect your brain as you age.”

“The fact that microbial profiles are responsible for these benefits paves the way for new nutrition-based prevention strategies to preserve cognitive function.”

of study Published in a magazine microbiome.

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J.nee others. 2026. Changes in total and different types of olive oil intake, gut microbiota, and cognitive function in older adults. microbiome 14, 68; doi: 10.1186/s40168-025-02306-4