Fish oil supplements may harm brain repair, new research suggests, challenging long-held assumptions about their universal benefits for cognitive health. While the compound has been widely promoted for its anti-inflammatory effects and role in fighting cardiovascular disease, a study published in Cell Reports indicates that a key omega-3 fatty acid can interfere with the brain’s ability to heal itself after injury.
The research, led by Onder Albayram, PhD, a neuroscientist and associate professor at the Medical University of South Carolina (MUSC) and a member of the National Trauma Society Committee, focused on eicosapentaenoic acid (EPA), a primary component of fish oil. The study found that EPA may disrupt the brain’s healing process following repeated mild traumatic brain injuries. Specifically, the compound appeared to weaken the stability of the walls of the brain’s blood vessels, making it harder for blood vessels to repair themselves after physical trauma. “Fish oil supplements are everywhere, and people take them for a range of reasons, often without a clear understanding of their long-term effects,” Albayram said. “We still don’t know whether the brain has resilience or resistance to this supplement.”
How EPA disrupts the brain’s blood vessel repair process
The study, which used both mouse models and human brain microvascular endothelial cells, demonstrated that EPA interferes with the repair signals the brain sends out after injury. By making the blood vessel walls less stable, the compound slows down the recovery process rather than aiding it. The researchers also discovered a link between long-term fish oil supplementation and the accumulation of tau protein in the brain’s cortex — a hallmark of neurodegenerative diseases such as Alzheimer’s and chronic traumatic encephalopathy (CTE). This build-up was particularly pronounced in cases involving repeated head injuries. Notably, the other major omega-3 fatty acid found in fish oil, docosahexaenoic acid (DHA), did not show the same negative effects in the study.
Albayram stressed that the findings do not amount to a blanket condemnation of fish oil. “I am not saying fish oil is good or bad in some universal way,” he said. “What our data highlight is that biology is context-dependent. We need to understand how these supplements behave in the body over time, rather than assuming the same effect applies to everyone.” The research focused on scenarios of repeated mild head injuries, meaning the results may not apply to individuals who have not suffered such trauma.
Broader context and the need for more research
The study adds a cautionary note to a body of evidence that has long been mixed. Previous research, including a large UK Biobank cohort study, has suggested that regular fish oil supplementation is associated with a lower risk of all-cause dementia, vascular dementia, and frontotemporal dementia — though not Alzheimer’s disease. Other studies have indicated that higher omega-3 levels in midlife are linked to better cognitive skills and brain structure, and that fish oil may reduce nerve cell breakdown in older adults at high risk for Alzheimer’s who carry the APOE-E4 gene variant. Some trials have also suggested that omega-3 supplements might improve symptoms in the early stages of dementia.
The public health stakes are high. In the UK, an estimated 982,000 people were living with dementia as of May 2024, a figure projected to rise to 1.4 million by 2040. Dementia was the leading cause of death across the UK in 2024, accounting for over 76,000 deaths. Current official guidance reflects the uncertainty. The NHS recommends eating at least two portions of fish per week, including one portion of oily fish, for general health benefits. However, the National Institute for Health and Care Excellence (NICE) does not recommend omega-3 supplements for treating depression, ADHD, or dementia, and advises against prescribing them for the primary or secondary prevention of cardiovascular disease.
Dr. Dung Trinh, an internist, has advised caution in interpreting the new findings, noting that brain health outcomes vary based on individual factors such as trauma history, vascular health, and metabolic status. The MUSC study’s authors emphasise that further research is needed to establish the full impact on humans, given that the principal effects were observed in mice and cell models.