, a new study suggested.
Data from a prospective study of more than 92,000 people showed consuming at least 7 g of olive oil a day — about half a tablespoon — was associated with a 28% lower risk for dementia-related death.
Replacing one teaspoon of margarine and mayonnaise with the equivalent amount of olive oil was associated with an 8%-14% lower risk for dementia-related mortality.
“Opting for olive oil, a natural product, instead of more processed fats such as margarine and mayonnaise, is a safe choice and may reduce risk of fatal dementia,” said lead investigator Anne-Julie Tessier, RD, PhD, research associate, Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston.
However, “intervention studies are needed to confirm causal effect and optimal quantity of olive oil intake,” she added.
The study was published online in JAMA Network Open.
A Spoonful of Olive Oil
A growing body of evidence has shown a link between the Mediterranean diet and preserved cognitive function and lower risk for cardiovascular disease (CVD). But its association with dementia mortality was unknown.
Investigators analyzed data on over 92,000 participants (66% women; mean age, 56 years) in the Nurses’ Health Study (NHS) and Health Professionals Follow-Up Study (HPFS) who were free of CVD and cancer at baseline.
Both studies were conducted between 1990 and 2018, with olive oil intake assessed every 4 years using a food frequency questionnaire. Dementia-related mortality was ascertained from death records.
The researchers also evaluated the joint association of diet quality (particularly adherence to the Mediterranean diet and Alternative Healthy Eating Index score) and olive oil consumption with the risk for dementia-related mortality. And they estimated the difference in the risk for dementia-related mortality when other dietary fats were substituted with an equivalent amount of olive oil.
There were 4751 dementia-related deaths during the 28-year follow-up period. People with two copies of the apolipoprotein epsilon-4 (APOE epsilon-4) allele — a known risk factor for Alzheimer’s disease — had a fivefold to ninefold greater likelihood of dementia-related death.
Compared with no or rare olive oil intake, consumption of 7 g of olive oil or more per day was associated with a 28% lower risk for dementia-related mortality (adjusted hazard ratio [HR], 0.72; P < .001), after adjusting for lifestyle and socioeconomic factors. The finding remained consistent even with further adjustment for the APOE epsilon-4 allele.
Each 5-g increment in olive oil consumption had an inverse association with dementia-related death in women (HR, 0.88; 95% CI, 0.84-0.93) but not in men (HR, 0.96; 95% CI, 0.88-1.04).
No interaction by diet quality scores was found.
No Link With Diet Quality
“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 between more olive oil and reduced risk of dementia-related death to be regardless of this factor,” Dr. Tessier said.
Replacing 5 g per day of margarine and mayonnaise with the equivalent amount of olive oil was associated with an 8%-14% lower risk for dementia mortality. Substitutions for other vegetable oils or butter were not significant.
“Some antioxidant compounds in olive oil can cross the blood-brain barrier, potentially having a direct effect on the brain,” Dr. Tessier said. “It is also possible that olive oil has an indirect effect on brain health by benefiting cardiovascular health.”
The authors noted several study limitations, including the possibility of reverse causation, due to the observational nature of the study.
It is also plausible that higher olive oil intake could be indicative of a healthier diet and higher socioeconomic status, although the results remained consistent after accounting these factors, the authors noted.
The study population included only healthcare professionals and was primarily non-Hispanic White people, which could limit generalizability.