A large cohort study suggests that not all olive oils are equal, with virgin olive oil showing favorable links to cognitive aging and gut microbiota profiles over two years.
Study: Total and different types of olive oil consumption, gut microbiota, and cognitive function changes in older adults. Image Credit: Mehes Daniel / Shutterstock
In a recent study published in the journal Microbiome, researchers examined the associations between olive oil intake, gut microbiota, and cognitive function in older adults.
Cognitive decline is a significant public health concern with a substantial impact on healthcare costs. Dietary patterns have emerged as preventive strategies to alleviate age-associated neurodegeneration and cognitive decline. Virgin olive oil (VOO), a major component of the Mediterranean diet, is well known for its high content of phenolic compounds and monounsaturated fats.
In contrast, common olive oil (COO) contains a greater proportion of olive-pomace oil or refined olive oil, with minimal VOO, resulting in lower levels of minor bioactive compounds despite a broadly similar fatty acid profile. Emerging evidence suggests that olive oil intake may benefit intestinal health and the gut microbiota. Despite preclinical insights into the relationship between VOO intake, gut microbiota, and cognitive function, human research remains limited.
Study Population and Design
Researchers evaluated the associations between olive oil intake, gut microbiota, and cognitive function in older adults. Individuals aged 55 to 75 years with overweight or obesity and metabolic syndrome were included from an ongoing randomized controlled trial, PREDIMED-Plus.
Participants completed a validated food frequency questionnaire administered repeatedly during follow-up, with baseline energy-adjusted intake used for the primary analyses. A neuropsychological test battery was administered at baseline and at the two-year follow-up.
Classification of Olive Oil Intake
Three questionnaire items focused on the consumption of different types of olive oils: virgin olive oil, refined olive oil, and olive-pomace oil.
Common olive oil intake was defined as the combined intake of olive-pomace and refined olive oils, while total olive oil (TOO) intake was defined as the consumption of all three types.
Cognitive Function Assessment and Scoring
Cognitive function was assessed using the clock drawing test, mini-mental state examination (MMSE), verbal fluency test, digit span test, and trail making test.
A z-score was calculated for each cognitive test at baseline and follow-up. These scores were aggregated to generate composite scores for neurocognitive domains such as executive function and attention.
Clock drawing test and MMSE scores were combined into a general cognitive function score. A global cognitive function score was computed by adding or subtracting individual z-scores based on whether higher scores indicated better or worse performance.
The primary outcome was the change in composite cognitive scores from baseline to follow-up.
Gut Microbiota Profiling and Analytical Approach
Stool samples collected at baseline were used for taxonomic profiling of the gut microbiota.
The analyses evaluated associations between olive oil intake and changes in cognitive function over follow-up, olive oil intake and gut microbiota composition and diversity at baseline, and olive oil–related microbial signatures and changes in cognitive function.
These analyses were observational within a randomized lifestyle trial cohort, as olive oil type intake was not randomized.
Participant Characteristics and Olive Oil Intake
The study included 656 adults with a mean age of 65 years.
The mean total olive oil intake was 30 g, 50 g, and 58 g per day in the lowest, intermediate, and highest tertiles, respectively.
Individuals in the intermediate tertile showed better baseline cognitive performance and a lower prevalence of depression, hypercholesterolemia, and type 2 diabetes. Participants in the highest tertile had higher smoking prevalence and lower educational levels.
Olive Oil Intake and Cognitive Changes
Participants in the highest tertile of total olive oil intake showed modest but statistically significant improvements in general cognitive function, attention, and global cognitive function compared with those in the lowest tertile.
Each 10 g per day increase in total olive oil intake was positively associated with changes in executive function, attention, and global and general cognitive function. Similar associations were observed for virgin olive oil intake, which appeared to drive most of the beneficial relationships.
In contrast, each 10 g per day increase in common olive oil intake was associated with worse changes in executive function, language, and global and general cognitive function.
Gut Microbiota Diversity and Olive Oil Type
Significant differences in alpha diversity indices were observed across common and virgin olive oil intake tertiles.
Higher virgin olive oil intake was associated with higher inverse Simpson and Chao1 diversity indices, while higher common olive oil intake was associated with lower alpha diversity.
No significant differences in alpha diversity were observed across total olive oil intake tertiles.
Taxonomic Associations With Olive Oil Intake
Nineteen bacterial genera were associated with olive oil intake after false-discovery rate correction.
Nine taxa were linked to total olive oil intake, 16 to virgin olive oil intake, and five to common olive oil intake, with Streptococcus, Adlercreutzia, and Eubacterium hallii group associated with all three exposures.
No significant associations were observed between alpha diversity indices and changes in cognitive function.
Microbial Taxa Linked to Cognitive Changes
Six microbial taxa were associated with changes in cognitive function, with only two remaining significant after correction.
Higher intakes of virgin and total olive oil were associated with reduced abundance of Adlercreutzia, which was negatively associated with changes in general cognitive function. Akkermansia was negatively associated with changes in attention.
Mediation by the Gut Microbiota
Mediation analyses suggested that gut microbiota may partially mediate the relationship between olive oil intake and changes in cognitive function.
Adlercreutzia was identified as a significant mediator of the association between virgin olive oil intake and improvements in general cognitive function, accounting for a small proportion of the total effect.
The indirect effects were modest and should be interpreted cautiously.
Implications for Cognitive Health and Aging
Overall, greater total and virgin olive oil intake was associated with more favorable cognitive changes over two years, while higher common olive oil intake was associated with less favorable cognitive trajectories.
The findings suggest that gut microbiota, particularly Adlercreutzia, may contribute to the association between olive oil intake and cognitive function, alongside metabolic, vascular, and anti-inflammatory mechanisms.
Further high-quality clinical studies are needed to clarify the efficacy of microbiota-targeted dietary strategies for promoting healthy aging and brain health.