In a prospective study in the large UK Biobank cohort, participants with higher plasma linoleic acid (LA) concentrations had a lower risk of incident dementia, whereas higher levels of non-LA omega-6 fatty acids were associated with an increased dementia risk.

The findings, published online ahead of print in The American Journal of Clinical Nutrition, add a nuance to the longstanding debate about omega-6 fats and brain health.

The study involved 273,795 UK Biobank participants who didn’t have dementia at baseline, followed for a median of 15.06 years. In that time, 5,799 dementia cases were identified.

The highest quintile for LA had an 18% lower incident dementia rate compared to the lowest quintile. However, the highest quintile for non-LA omega-6 fatty acids experienced a 21% greater rate of dementia than the lowest quintile.

“These results reinforce a critical point: we shouldn’t treat omega-6 fatty acids as a single, interchangeable group,” said William S. Harris, PhD, senior author and president of the Fatty Acid Research Institute (FARI). “In this analysis, the largest of its kind, linoleic acid tracked with lower dementia risk, while other omega-6 fats tracked with higher risk, an important distinction for researchers and clinicians.”

The study authors adjusted for multiple factors related to dementia risk, and while the study is observational in nature, it provides evidence that different omega-6 fatty acids have meaningfully different associations with long-term cognitive health outcomes.

Among the participants, LA constituted 75% of the plasma omega-6 fatty acids on average, while the remaining 25% were made up of six other fatty acids. Of these remaining fatty acids, arachidonic acid made up 77%.

The five other omega-6s – gamma-linolenic, dihomo-gamma-linolenic, eicosadienoic, adrenic, and docosapentaenoic acid – made up 5.8% of plasma omega-6 fatty acids in the cohort.

“Nutrition debates often get oversimplified,” said Aleix Sala-Vila, PhD, lead author of the study. “Our findings support the growing view that ‘omega-6’ is not one thing, and they motivate future work to test whether dietary patterns that raise linoleic acid may help reduce dementia risk.”

The authors noted that it remains to be seen why LA may potentially offer cognitive benefits relative to other omega-6s.