A Spanish study tracked more than 600 older adults for two years and found that extra virgin olive oil was linked with better cognitive performance and a richer gut microbiome compared with refined olive oil; the research highlights differences in processing, possible microbiome-driven mechanisms, and important study limitations that stop short of proving direct cause and effect.
The study followed participants aged 55 to 75 who were overweight or obese and carried metabolic risk factors. Researchers recorded which type of olive oil people used and sampled their gut microbiota over the study period. The results targeted cognitive tests alongside microbial diversity measures to draw a connection between diet and brain function.
People who relied on virgin olive oil showed improved cognitive scores and a more diverse gut biome, which researchers treated as “an important marker of intestinal and metabolic health.” “This is the first prospective study in humans to specifically analyze the role of olive oil in the interaction between gut microbiota and cognitive function,” the team wrote, tying the two outcomes together as linked observations. The contrast with refined oil was clear: those using refined oil tended to show stagnation or loss of microbial variety over time.
The investigators point to the processing gap between oil types as a likely reason for the difference. Refined olive oil is subjected to industrial treatments that remove impurities but also strip away many of the natural antioxidants and vitamins that extra virgin varieties retain. Those bioactive compounds can influence gut ecology and systemic inflammation, which makes the microbiome a plausible mediator between diet and cognition.
On cognitive measures, the group consuming extra virgin olive oil scored better in memory, attention, and executive function tests across the two years of follow-up. Refined oil did not produce these same gains, prompting researchers to warn that “Not all olive oils have benefits for cognitive function,” and suggesting shoppers should consider quality, not just quantity. The pattern suggests that beyond calories and fat totals, the type of fat and its micronutrient content matter for aging brains.
Readers should note important caveats: the trial was observational and focused on older Mediterranean adults with metabolic syndrome, so the findings may not generalize to everyone and do not establish direct causation. The authors acknowledged that lifestyle differences—such as smoking or education level—were more common among refined oil users and could influence outcomes, even after statistical adjustments. Diet data were self-reported, which always introduces some uncertainty into nutritional studies.
Investigators and commentators framed the takeaway around food quality and long-term health strategy. Jordi Salas-Salvadó emphasized that “Extra virgin olive oil not only protects the heart but can also help preserve the brain during aging,” calling attention to overlapping benefits for cardiovascular and cognitive health. The study appears in the journal Microbiome and adds to a growing body of research that links dietary patterns, microbial ecosystems, and mental sharpness as people age.
