Adding fish oil to your daily diet has been shown to have a variety of benefits on mood, brain health, and reducing the risk of developing brain lesions thought to be a visible marker of cognitive decline.
But what of older adults who already have damage to their brain's white matter? Could fish oil tablets put the brakes on damage and slow the progress of conditions like Alzheimer's disease?
A team from the Oregon Health & Science University (OHSU) investigated the effects of omega-3 fatty acids found in fish oil on a cohort of 102 volunteers who were aged 75 to 95, with few to no signs of cognitive impairment in spite of the beginnings of neurological damage known as white matter lesions.
While omega-3 fatty acids didn't make much of a difference in the group as a whole during the three years of study, it did make a significant improvement to the rate of damage accumulating in one sub-group: individuals carrying the APOE4 gene, which has been linked to a higher Alzheimer's risk.
While the treatment didn't seem to affect the white matter lesions' growth rates, for those with a genetic disposition to Alzheimer's there were "significant reductions" in the breakdowns of nerve cells – another key indicator of brain health.
"The fact that neuronal integrity breakdown was slowed in people randomized to omega-3 treatment who are also at high risk for Alzheimer's disease is remarkable, and warrants a larger clinical trial in more diverse populations in the future," says neurologist Gene Bowman, who was at OHSU when the research was carried out.
The findings suggest fish oil supplements won't prevent or slow the progress of dementia generally, but might benefit some individuals who are at risk.
"Our findings showed that over three years, there was not a statistically significant difference between placebo and the group that took fish oil," says neurologist Lynne Shinto, from OHSU. "I don't think it would be harmful, but I wouldn't say you need to take fish oil to prevent dementia."
The researchers want larger clinical trials to be carried out to analyze the link between APOE4 carriers, the progression of dementia, and omega-3 fatty acids, which should give us a better idea of the influence fish oil may potentially have.
Alzheimer's is a complex disease, but every study on it gets us closer to a full understanding of the condition and how to beat it – and research carried out as comprehensively as the study here is particularly helpful in identifying how adn why different people's brains age differently.
"This is the first dementia prevention trial to use modern prevention tools, such as a blood test and brain scan, to identify not only people at high risk for dementia, but also those well-suited to receive a specific nutritional intervention," says Bowman.
The research has been published in JAMA Network Open.