Fish oil may be beneficial for older adults who have a genetic predisposition to Alzheimer's disease, a new study has revealed.
The research, published in JAMA Network Open, found that fish oil supplements caused a "remarkable" reduction in the breakdown of brain nerve cells in individuals with a gene linked to Alzheimer's disease.
Lynne Shinto, a study co-author and professor of neurology at the Oregon Health & Science University (OHSU) School of Medicine, said that fish oil could be particularly valuable for those who carry the APOE4 gene, which is associated with a higher risk of developing Alzheimer's.
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In APOE4 carriers, the study observed a "dramatic reduction" in the loss of brain cell integrity within just one year of fish oil treatment, compared to those taking soybean oil.
"This is an exciting study with valuable new findings to guide future research into ways to prevent or slow cognitive decline and onset of Alzheimer's Disease," Philip Calder, professor of nutritional immunology at the U.K.'s University of Southampton, told Newsweek.
"It is important to note that the findings of this new trial are consistent with earlier observational studies suggesting a link between higher omega-3 intake, or higher omega-3s in the blood, and slower cognitive decline."
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He added that omega-3 fatty acids, particularly EPA and DHA, are well-known for their role in reducing inflammation in blood vessel walls. This reduction in inflammation is beneficial for lowering the risk of heart disease. Consequently, dietary guidelines suggest regularly consuming omega-3s, preferably through fish, to leverage these health benefits.
Calder also emphasized the need for this trial to be replicated with a larger cohort, especially targeting individuals who are genetically at risk.
"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," Gene Bowman, director of clinical trials and instructor of neurology at Massachusetts General Hospital and Harvard Medical School, said in a statement.
"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."
The study enlisted 102 participants who were 75 years old or older and had relatively low blood levels of omega-3 fatty acids, which are found in fish oil.
Participants underwent brain MRIs at the start and again at the end of the three-year study to assess changes in white matter lesions.
These lesions can impair nutrient delivery through blood vessels to the brain, increasing the risk of developing dementia later in life. The participants, who had relatively high levels of white matter lesions but no dementia, were otherwise healthy.
Half of the patients took omega-3-enriched fish oil supplements daily, while the other half received a soybean-based placebo.
MRIs conducted at the beginning and end of the study showed a slight reduction in the progression of white matter lesions in the fish oil group. However, this difference was not statistically significant when compared to the placebo group.
As a result, the study did not find a clear benefit for all older adults, and fish oil may not be effective for everyone in this age group, according to Lynne Shinto, professor of neurology at the OHSU School of Medicine.
"I don't think it would be harmful, but I wouldn't say you need to take fish oil to prevent dementia," she said in a statement.
Calder, who acknowledges that the length of the trial was necessary since changes in the brain occur very slowly, said that the lack of statistical significance likely occurred because the number of people being studied was too low.
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