A prospective study involving 90,000 healthcare professionals found that higher olive oil intake is linked to a reduced risk of dementia-related mortality.
Consuming at least 7 grams of olive oil daily—about half a tablespoon—was associated with a 28% lower risk of death due to dementia (pooled hazard ratio [HR] 0.72, 95% CI 0.64-0.81) compared to those who rarely or never consumed olive oil (P for trend <0.001) over a 28-year follow-up period, reported Anne-Julie Tessier, RD, PhD, from Harvard T.H. Chan School of Public Health, and her co-authors.
Small Changes to Diet
This relationship remained significant even after adjusting for diet quality, including adherence to a Mediterranean diet, and the presence of the APOE4 gene, according to the researchers in JAMA Network Open.
Replacing 5 grams (about 1 teaspoon) of margarine or mayonnaise with an equivalent amount of olive oil daily was associated with an 8-14% lower risk of dementia mortality.
Difficult to Study
However, substituting other vegetable oils or butter was not significant.
Dementia onset is gradual and progression is slow, making dementia-related mortality challenging to study, noted Tessier. “To our knowledge, this is the first study to examine diet, specifically olive oil, in relation to dementia death,” she told MedPage Today.
Healthier Alternative
“Typically, people who use olive oil for cooking or as a dressing have an overall better quality of their diet, but interestingly, we found the association to be regardless of this factor,” Tessier highlighted.
“Current dietary guidelines regarding fats are mainly based on evidence related to cardiovascular health,” she added.
Linked to Brain Health
Tessier states “Our study contributes to supporting current dietary guidelines recommending choosing vegetable oils such as olive oil, but extends these recommendations to brain-related health.”
Several observational studies have found links between brain health and plant-based diets, such as the Mediterranean or MIND diet, which include olive oil.
Possibly Unrelated
However, some research has suggested that diet and dementia may not be related.
“As part of the Mediterranean diet, olive oil may exert anti-inflammatory and neuroprotective effects due to its high content of monounsaturated fatty acids and other compounds with antioxidant properties such as vitamin E and polyphenols,” Tessier and her colleagues noted.
28 Years of Study
The researchers tracked 60,582 women from the Nurses’ Health Study and 31,801 men from the Health Professionals Follow-up Study from 1990 to 2018.
Previous research from these cohorts indicated that higher olive oil consumption was associated with lower risks of cardiovascular disease and neurodegenerative disease mortality.
Assessing Health Effects
The mean baseline age was about 54, and participants were initially free of cardiovascular disease and cancer. Dementia death was determined from death records.
Every four years, participants reported their olive oil intake through food frequency questionnaires. Overall diet quality was assessed using scores from the Alternative Healthy Eating Index and the alternative Mediterranean diet scale.
Olive Oil Intake May Reduce Risk of Dementia
The mean olive oil intake at baseline was 1.3 grams per day, which increased over time. During the 28-year follow-up, 4,751 dementia-related deaths occurred.
The significant association between olive oil intake and reduced dementia-related death was observed in women (adjusted HR 0.67, 95% CI 0.59-0.77), but not in men (HR 0.87, 95% CI 0.69-1.09). Joint analyses indicated that participants with high olive oil intake had a low risk for dementia-related mortality, regardless of their diet quality scores.
Promising Results
In a subset of approximately 27,000 participants who were genotyped, the results were similar after adjusting for the presence of an APOE4 allele (adjusted HR comparing high vs. low olive oil intake of 0.66, 95% CI 0.54-0.81, P for trend <0.001).
Olive oil consumption may reduce dementia mortality by improving vascular health, Tessier and colleagues suggested.
Limitations of the Study
However, incident cardiovascular disease, hypercholesterolemia, hypertension, and diabetes were not significant mediators of the relationship between olive oil and dementia-related death in this study.
The study had several limitations, including the potential for reverse causation, the researchers acknowledged.
Potential Areas of Improvement
Despite consistent results after accounting for socioeconomic status and other important covariates, residual confounding may have occurred. The study population was predominantly white, so the findings may not be generalizable to other groups.
Additionally, during the study period, some margarine and mayonnaise contained significant levels of partially hydrogenated oils, which the FDA warned about in 2013 and subsequently banned.
