Fish oil supplements have a slippery reputation when it comes to preventing cognitive decline, the hallmark symptom of Alzheimer’s disease. Studies have provided ambiguous results, promoting recommendations founded more on faith than evidence. But new research published in the journal Alzheimer’s & Dementia shows promise that regularly taking fish oil supplements may in fact reduce cognitive decline, if your genetic makeup doesn’t stand in the way.
The research, led by Lori Daiello, a scientist at the Alzheimer’s Disease and Memory Disorders Center at Rhode Island Hospital, looked at cognitive performance and brain atrophy in 819 older adults enrolled in the large multi-center Alzheimer’s Disease Neuroimaging Initative started in 2004. Of those who did not have dementia at the start of the study, regularly taking fish oil supplements was linked to a reduction in rates of cognitive decline as well as brain shrinkage. The findings are the first to measure both cognitive and brain volume changes in an aging population that regularly takes fish oil supplements.
The results seem to suggest that regularly taking fish oil before potential cognitive decline kicks in is a good idea. But there’s an important caveat: The positive results were only found in participants without the best-studied genetic risk factor for Alzheimer’s—the APOE ε4 gene. Individuals with the genetic marker were unaffected by the supplement. This could be due in part to their inability to properly metabolize DHA, the essential fatty acid present in fish oil supplements, the authors note.
Still, there is not enough evidence to declare that fish oil pills are entirely unproductive for those with a genetic risk for Alzheimer’s. It is possible, the authors write, that “adequate levels of long-chain fatty acids before or during middle age might mitigate early neurodegenerative processes in at-risk individuals.”
Certainly researchers should account for those with risky DNA in future studies. With Alzheimer’s estimated to affect more than 44 million people worldwide—diagnosed in at least one person every four seconds—and still without a cure, it’s clear that investigating means for prevention and early detection are essential.