The blood-brain barrier is a collection of membranes that separate the central nervous system from the peripheral circulation, facilitating the passage of nutrients and signaling compounds while excluding harmful substances. Loss of blood-brain barrier integrity increases the risk of many neurodegenerative diseases, including dementia and Alzheimer’s. A 2021 study found that having a higher omega-3 index preserves the blood-brain barrier and maintains cognitive function in older adults.

Researchers assessed the cognitive performance of 45 healthy older adults. They measured the participants' red blood cell omega-3 concentrations (“omega-3 index”) and evaluated their blood-brain barrier integrity using magnetic resonance imaging.

They found that participants with a higher omega-3 index had greater blood-brain barrier integrity than those with a lower index. They also performed better on tests of memory and language (functions most affected by Alzheimer’s disease) but not on executive function, speed, or motor control assessments.

These findings suggest that higher blood concentrations of omega-3 fatty acids (measured via the omega-3 index) preserve blood-brain barrier integrity, potentially protecting against cognitive losses. The omega-3 index measures the amount of the omega-3 fatty acids EPA and DHA as a percentage of total fatty acids in red blood cell membranes. Evidence suggests it is a reliable biomarker of sudden cardiac death risk and may provide a means of standardizing methodologies used in clinical trials, facilitating more accurate interpretation of clinical trial outcomes. Learn more about the omega-3 index in our overview article.