Popular brain supplement could have an unexpected downside, researchers warn

Fish oil supplements have become ubiquitous. People pop them thinking they're helping their brain health. But a new study suggests that one of the main omega-3 fatty acids in these supplements might actually interfere with the brain's ability to repair itself after injury.


Researchers at the Medical University of South Carolina published findings in Cell Reports showing that EPA (eicosapentaenoic acid), one of the key omega-3s in fish oil, could get in the way of blood vessel repair in the brain. The study, conducted on mice that experienced mild traumatic head injuries, found something counterintuitive: animals fed diets containing EPA performed worse on spatial memory and learning tasks after the injuries compared to controls.


This challenges the long-standing belief that omega-3s help the brain recover which is a reason why it is so popular among health enthusiasts.


Another omega-3 fatty acid called DHA (docosahexaenoic acid) didn't cause the same problems. When researchers tested DHA separately using human brain cell samples, it didn't interfere with repair processes. This means the problem is specific to EPA, not all omega-3s.


The researchers found that EPA accumulates more readily in the brain than DHA, and once it's there, it reprograms how cells use energy. In injured brains trying to repair themselves, this metabolic shift became problematic. The EPA seemed to divert resources away from the actual repair work happening.


What's particularly concerning is that the disruption led to a buildup of toxic tau proteins in the brains of mice fed EPA. Tau protein buildup is associated with brain degeneration and chronic traumatic encephalopathy (CTE), the degenerative condition linked to repeated head injuries like those sustained by athletes or military personnel.


To see if this mattered beyond mice, researchers examined human brain tissue from people with CTE. They found similar patterns—the same kind of metabolic disruption and blood vessel damage. This suggests the findings from the animal studies might have relevance for humans, though researchers stressed that much more testing is needed.