A new study published in The Journal of Nutrition reveals that higher levels of certain omega-3 fatty acids in the blood — particularly DHA and ALA — are associated with better cognitive performance over time in middle-aged adults at high risk of developing Alzheimer’s disease (AD).
The research, conducted within the ALFA (Alzheimer and Families) Study, followed 323 cognitively unimpaired participants during a three-year period.
The scientists analysed red blood cell (RBC) concentrations of three omega-3 fatty acids: docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and alpha-linolenic acid (ALA).
They found that participants with higher DHA levels showed slower cognitive decline, while higher ALA levels were linked to stronger visual processing abilities.
Key Findings
The researchers uncovered the following findings:
- DHA and global cognition: participants with higher DHA levels demonstrated a more favourable rate of change in overall cognitive performance, measured using the Preclinical Alzheimer Cognitive Composite (PACC)
- ALA and visual processing: higher blood levels of plant-derived ALA were linked to improved performance in visual processing tasks
- EPA not significantly associated: no statistically significant associations were observed between EPA and cognitive performance
- Consistency across risk groups: the associations between omega-3 status and cognition were similar regardless of sex, APOE-ε4 genotype, or underlying Alzheimer’s pathology detected through cerebrospinal fluid (CSF) biomarkers.
The study’s statistical models controlled for several variables, including age, sex, education, physical activity, Mediterranean diet adherence and APOE-ε4 status.
Even after accounting for these factors, DHA emerged as a significant predictor of better cognitive trajectories.
“Our findings reinforce the idea that diet-linked omega-3 fatty acids are important for long-term brain health,” said Dr Aleix Sala-Vila, Research Scientist at the Fatty Acid Research Institute (FARI) and senior researcher in the ALFA project.
“While DHA from fish has long been associated with brain structure and function, our results also point to potential benefits from ALA, a plant-based omega-3 fatty acid."
"ALA may be particularly relevant for people with low fish consumption.”
Alzheimer’s disease remains the leading cause of dementia worldwide, with limited options for treatment once symptoms appear.
Identifying modifiable lifestyle and nutritional factors that can delay or prevent disease onset has become a major global health priority.
The ALFA study’s focus on individuals in the preclinical phase of Alzheimer’s — those who show no symptoms but carry biological or genetic risk markers — offers critical insight into early preventive strategies.
“These results suggest that maintaining adequate omega-3 fatty acid levels through diet or supplementation may help preserve cognitive function before the onset of Alzheimer’s symptoms,” said Dr Bill Harris, founder of OmegaQuant and President of the Fatty Acid Research Institute (FARI).
“Longer and larger studies, including randomised clinical trials, are needed to confirm causality.”