A major prospective study in the UK Biobank reported higher plasma linoleic acid (LA)—the most common omega-6 fatty acid in the diet—was associated with a lower risk of incident dementia. Higher levels of non-LA omega-6 polyunsaturated fatty acids (n-6 PUFAs) were associated with a higher risk.
The findings were published in the American Journal of Clinical Nutrition and add important nuance to longstanding debate about omega-6 fats and brain health. LA was associated with an 18 percent lower dementia risk and non-LA n-6 PUFAs were associated with a 21 percent higher dementia risk.
The authors used objective blood biomarkers (plasma fatty acids) and adjusted for multiple factors reported to relate to dementia risk. The study is observational and cannot prove cause-and-effect, but provides strong evidence that different omega-6 fatty acids may have meaningfully different associations with long-term brain outcomes.
The “why” question still remains, “why would high levels of the major omega-6 (LA) be associated with lower dementia risk while high levels of other omega-6s are associated with higher risk?”
According to researchers, LA constitutes 75 percent of the plasma omega-6 fatty acids and six other omega-6s together make up the other 25 percent, and of this, arachidonic acid (AA) is the major player at 77 percent.
The five other omega-6s only make up 5.8 percent of the plasma omega-6 fatty acids. Researchers believe that “non-LA n6” would essentially be AA, but this needs further study since the analytical method used in this study is not strongly correlated with plasma AA levels.
“Nutrition debates often get oversimplified. 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 plasma linoleic acid may help reduce dementia risk,” said Aleix Sala-Vila, PhD, lead author of the study.
“These results reinforce a critical point: we shouldn’t treat omega-6 fatty acids as a single, interchangeable group. 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,” added William S. Harris, PhD, senior author and president of the Fatty Acid Research Institute (FARI).
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