Daily Olive Oil Consumption Linked to Lower Dementia Death Risk, Study Finds

A new study from Harvard University has found that con­sum­ing half a table­spoon of olive oil daily is asso­ci­ated with a lower risk of demen­tia-related death.

The researchers exam­ined data col­lected from 92,383 United States adults par­tic­i­pat­ing in the Nurses’ Health Study and Health Professionals Follow-Up Study over 28 years.

They found that daily con­sump­tion of at least seven grams of olive oil was asso­ci­ated with a 28 per­cent lower risk of demen­tia-related death com­pared with those who never or rarely con­sumed olive oil.

The asso­ci­a­tion between olive oil con­sump­tion and Alzheimer’s dis­ease, the most com­mon form of demen­tia, has been long estab­lished. However, it is increas­ingly of inter­est to researchers as the preva­lence of demen­tia con­tin­ues to rise.

World Health Organization data show that more than 55 mil­lion peo­ple had demen­tia world­wide in 2023. Separate research pub­lished in The Lancet pre­dicted that demen­tia rates are set to triple by 2050.

According to Scott Small, the direc­tor of Columbia University’s Alzheimer’s Disease Research Center, demen­tia impacts the deep­est part of the brain in its final stages, which can inhibit bod­ily func­tions, includ­ing heart rate and breath­ing.

While res­pi­ra­tory or uri­nary tract infec­tions are fre­quent causes of death in late-stage demen­tia patients, those receiv­ing the high­est qual­ity care essen­tially die from accu­mu­lated brain cell death.

The study also exam­ined the asso­ci­a­tion between total olive oil con­sump­tion and diet qual­ity, includ­ing adher­ence to the Mediterranean diet and the Alternative Healthy Eating Index.

The researchers found that par­tic­i­pants with the high­est olive oil intake had a lower risk of demen­tia-related death regard­less of their adher­ence to either diet. ​“This high­lights a poten­tially spe­cific role for olive oil,” the researchers wrote.

“Still, the group with both high Alternative Healthy Eating Index scores and high olive oil intake exhib­ited the low­est demen­tia mor­tal­ity risk, sug­gest­ing that com­bin­ing higher diet qual­ity with higher olive oil intake may con­fer enhanced ben­e­fit,” they added.

The study also inves­ti­gated the impact of replac­ing other dietary fats with olive oil.

The researchers found that replac­ing five grams of may­on­naise with the equiv­a­lent amount of olive oil was asso­ci­ated with a 14 per­cent lower risk of demen­tia-related death. Meanwhile, replac­ing five grams of mar­garine with olive oil was asso­ci­ated with an eight per­cent lower risk.

No sta­tis­ti­cally sig­nif­i­cant dif­fer­ence was observed when replac­ing but­ter or other veg­etable oils with olive oil.

“These find­ings pro­vide evi­dence to sup­port dietary rec­om­men­da­tions advo­cat­ing for the use of olive oil and other veg­etable oils as a poten­tial strat­egy to main­tain over­all health and pre­vent demen­tia,” the researchers wrote.

However, they acknowl­edged that at the time of the study, may­on­naise and mar­garine con­tained high lev­els of hydro­genated trans-fats, which are strongly asso­ci­ated with car­dio­vas­cu­lar dis­ease, type 2 dia­betes and demen­tia. In 2020, U.S. health author­i­ties banned man­u­fac­tur­ers from adding par­tially hydro­genated oils to foods.

Anne-Julie Tessier, the study’s lead author and a research asso­ciate in nutri­tion at Harvard’s T.H. Chan School of Public Health, told Olive Oil Times that the researchers believe antiox­i­dants found in olive oil may play a role in the asso­ci­a­tion between its con­sump­tion and lower risk of demen­tia-related death.

“We think that some com­pounds with antiox­i­dant activ­ity in olive oil can cross the blood-brain bar­rier, poten­tially hav­ing a direct effect on the brain,” she said. ​“It is also pos­si­ble that olive oil has an indi­rect effect on brain health by ben­e­fit­ing car­dio­vas­cu­lar health, although we accounted for such fac­tors in our mod­els, and the asso­ci­a­tions remained.”

The study pop­u­la­tion included 60,582 women from the Nurses’ Health Study and 31,801 men from the Health Professionals Follow-Up Study with an aver­age age of 56 and who were free of car­dio­vas­cu­lar dis­ease and can­cer at base­line. Olive oil con­sump­tion was assessed every four years using a food fre­quency ques­tion­naire.

“This involved ask­ing par­tic­i­pants a range of ques­tions about how often they con­sumed olive oil, whether it was for salad dress­ings, cook­ing pur­poses or added to other foods,” Tessier said.

“However, we did not have data allow­ing us to dif­fer­en­ti­ate the type of oil used,” she added. ​“Thus, we observed an asso­ci­a­tion regard­less of the type of olive oil used, whether it was vir­gin or not, and whether it was used for cook­ing, in salad dress­ings or added to other foods.”

One of the study’s main strengths was the analy­sis of sev­eral sub­groups, includ­ing indi­vid­u­als with the apolipopro­tein ε4 (APOE ε4) geno­type. Individuals with homo­ge­neous APOE ε4 alle­les are five to nine times more likely to die of demen­tia.

“Exploratory sub­group analy­ses showed asso­ci­a­tions between higher olive oil intake and lower risk of demen­tia-related mor­tal­ity across most sub­groups,” the researchers wrote. ​“No sta­tis­ti­cally sig­nif­i­cant asso­ci­a­tions were found in par­tic­i­pants with a fam­ily his­tory of demen­tia, liv­ing alone, using a mul­ti­vi­t­a­min and in non – APOE ε4 car­ri­ers.”

While the study’s other strengths included the long fol­low-up period, large sam­ple size and high num­ber of demen­tia death cases, the researchers acknowl­edged its lim­i­ta­tions.

“Our study can­not estab­lish a causal effect of olive oil because it is not an inter­ven­tion study,” Tessier said.

The researchers also wrote that the study pop­u­la­tion was not rep­re­sen­ta­tive of the wider pub­lic in the United States since it mostly com­prised health­care pro­fes­sion­als, the vast major­ity of whom were older and white.

Tessier said future stud­ies should pro­vide olive oil to par­tic­i­pants to assess its impact on cog­ni­tive func­tion and see if a direct effect can be observed.

“However, it is impor­tant to note that for most demen­tia types, the onset is grad­ual, and the pro­gres­sion of the dis­ease is slow,” she con­cluded. ​“Because of this, we must wait a long time for the cases to occur. Dementia and demen­tia mor­tal­ity can hardly be stud­ied in a design other than obser­va­tional.”

• Columbia University’s Alzheimer’s Disease Research Center
• World Health Organization