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A large cohort study suggests that not all olive oils are the same, with virgin olive oil showing positive links to cognitive ageing and gut microbiome profiles over two years.
In a recent study published in the journal Microbiome, researchers examined the associations between olive oil intake, the gut microbiome, and cognitive function in older adults.
Cognitive decline is a major public health concern with a significant impact on healthcare costs. Dietary patterns have emerged as preventive strategies to reduce age-related neurodegeneration and cognitive decline.
Virgin olive oil (VOO), a key component of the Mediterranean diet, is known for its high content of phenolic compounds and monounsaturated fats. In contrast, common olive oil (COO) contains a higher proportion of pomace oil or refined olive oil and only a small amount of virgin olive oil, resulting in lower levels of secondary bioactive compounds despite a broadly similar fatty acid profile.
Emerging evidence suggests that olive oil intake may benefit gut and microbiome health. However, despite preclinical insights into the relationship between virgin olive oil intake, the gut microbiome, and cognitive function, human research remains limited.
The researchers assessed associations between olive oil intake, the gut microbiome, and cognitive function in older adults. The study included people aged 55 to 75 years with overweight or obesity and metabolic syndrome, as part of the ongoing randomized controlled PREDIMED-Plus trial.
Participants completed a validated food-frequency questionnaire, administered repeatedly during follow-up, with energy-adjusted baseline intake used for primary analyses. A battery of neuropsychological tests was performed at baseline and after two years of follow-up.
Three questionnaire items focused on the consumption of different olive oil types: virgin olive oil, refined olive oil, and pomace olive oil.
Cognitive function was assessed using several tests, including the clock drawing test, the Mini-Mental State Examination (MMSE), verbal fluency, digit span, and the trail-making test.
A standardized Z-score was calculated for each cognitive test at baseline and follow-up. These scores were combined to generate composite scores for neurocognitive domains such as executive function and attention.
The clock drawing test and MMSE scores were combined into a general cognitive function score. An overall cognitive function score was also calculated by adding or subtracting individual standardized scores depending on whether higher scores reflected better or worse performance.
The primary outcome was the change in composite cognitive scores from baseline to follow-up.
Stool samples collected at baseline were used for taxonomic profiling of the gut microbiome. The analyses assessed associations between olive oil intake and changes in cognitive function, olive oil intake and gut microbiome composition and diversity at baseline, and microbial signatures associated with olive oil intake and their relationship with cognitive changes.
These analyses are observational within a randomized lifestyle trial, as participants were not randomly assigned to a specific type of olive oil intake.
The study included 656 adults with an average age of 65 years. Median total olive oil intake was 30 grams, 50 grams, and 58 grams per day in the lower, middle, and upper intake tertiles, respectively.
People in the middle tertile showed better cognitive performance at baseline and lower prevalence of depression, hypercholesterolemia, and type 2 diabetes. Participants in the highest tertile had a higher prevalence of smoking and lower education levels.
Participants in the highest tertile of total olive oil intake showed modest but statistically significant improvements in general cognitive function, attention, and overall cognitive function compared with those in the lowest tertile.
Statistically significant differences in alpha-diversity indices were observed across intake tertiles of common and virgin olive oil. Higher virgin olive oil intake was linked to higher diversity indices, including inverse Simpson and Chao1, while higher common olive oil intake was associated with lower alpha diversity.
No statistically significant differences in alpha diversity were observed across total olive oil intake tertiles.
Nineteen bacterial genera were associated with olive oil intake. Nine taxa were associated with total olive oil intake, 16 with virgin olive oil, and five with common olive oil. Streptococcus, Adlercreutzia, and the Eubacterium hallii group were associated with all three oil categories.
No statistically significant associations were observed between alpha-diversity indices and changes in cognitive function.
Six microbial taxa were associated with changes in cognitive function.
Mediation analyses suggested that the gut microbiome may partly mediate the relationship between olive oil intake and changes in cognitive function. Adlercreutzia was identified as an important mediator of the association between virgin olive oil intake and improvements in general cognitive function, accounting for a small share of the overall effect.
The indirect effects were modest and should be interpreted cautiously.
Overall, higher 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 the gut microbiome, particularly Adlercreutzia, may contribute to the link between olive oil intake and cognitive function, alongside metabolic, vascular, and anti-inflammatory mechanisms.
More high-quality clinical studies are needed to clarify the effectiveness of microbiome-targeted dietary strategies for healthy ageing and brain health.
Source: News Medical