Having higher blood concentrations of the omega-3 fatty acids DHA and ALA was linked to better cognitive performance over time in middle aged adults at high risk of developing Alzheimer’s disease (AD), a new study found.

The findings, which relied on data from the ALFA (Alzheimer and Families) study, followed 323 cognitively unimpaired participants over three years. The authors analyzed red blood cell counts of the omega-3 fatty acids EPA, DHA, and ALA. Participants underwent a battery of cognitive tests at baseline and again after three years, assessing domains such as memory, attention, executive function, language, and visual processing.

Participants who had a higher amount of DHA showed slower measures of cognitive decline over the study period, as measured using the Preclinical Alzheimer Cognitive Composite (PACC). Higher ALA levels were linked to stronger visual processing performance measures, the researchers found, as measured by multiple visual processing tasks.

There were no significant associations observed between EPA and cognitive performance.

The subgroup analysis revealed that DHA’s and ALA’s protective effects were consistent across several variables, including age, sex, education, physical activity, Mediterranean diet adherence, and APOE-ε4 status.

“Our findings reinforce the idea that diet-linked omega-3 fatty acids are important for long-term brain health,” said Aleix Sala-Vila, PhD, research scientist at the Fatty Acid Research Institute (FARI), principal investigator at Hospital del Mar Research Institute, 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, which may be particularly relevant for people with low fish consumption.”

Alzheimer’s disease remains the leading cause of dementia worldwide, with limited options for treatments once symptoms appear, noted FARI. Lifestyle and nutritional factors that can delay or prevent disease onset has become a major priority as a result. ALFA, in focusing on the preclinical phase of Alzheimer’s in which people show no symptoms but carry biological or genetic risk markers, offers important insight into preventive strategies, the organization reported.

“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 Bill Haris, PhD, founder of OmegaQuant and president of FARI. “Longer and larger studies, including randomized clinical trials, are needed to confirm causality.”