Could fish oil benefit people at high risk of Alzheimer's disease?

• Over the years, many claims have been made for the health benefits of fish oils.
• Now, a study has found that taking fish oil supplements in later life could help reduce the risk of Alzheimer’s in some people.
• The small study showed that in older people with a gene that increases Alzheimer’s risk, fish oil supplements reduced the breakdown of nerve cells in the brain.
• Experts suggest that larger clinical trials should investigate the benefits of omega-3 supplements for those at high risk of Alzheimer’s.

Oily fish is part of a healthful diet as it is a good source of omega-3 fatty acids (omega-3 PUFAs). Those who do not include oily fish in their diet may take fish oil supplements which are often advocated as having a number of health benefits , including:

• Heart and cardiovascular benefits
• Protecting eye health
• Healthy fetal development
• Memory and other mental health benefits.

However, some of the health claims for fish oils are disputed, and taking supplements may be associated with health risks in some people.

Now, a small study has found that fish oil supplements could be beneficial for older people with the APOEε4 gene that increases the risk of developing Alzheimer’s disease.

The study, which is published in JAMA Network Open , found reduced nerve cell breakdown in those with the gene who were given fish oil, but no significant benefit for people without the gene.

“This study highlights the potential for personalized nutritional interventions based on genetic predisposition. The results are promising, but more extensive research is necessary to fully understand the implications and to establish definitive guidelines. It’s also crucial to continue exploring other lifestyle and dietary factors that can contribute to brain health in older adults.”
— Dr. Steve Allder , consultant neurologist at Re:Cognition Health, spekaing to Medical News Today

The Alzheimer’s risk gene

According to the Alzheimer’s Association , there are several factors that may increase a person’s risk of developing Alzheimer’s disease. These include:

• Age
• Smoking
• An unhealthy diet and/or overweight
• Lack of exercise
• Family history and genetics.

A number of genes have been identified that are linked to Alzheimer’s, of which the best known is the APOE gene.

One version of this, APOEε4, increases the risk of developing Alzheimer’s, particularly in those who inherit APOEε4 from both their parents.

3 soft gel fish oil capsules a day

The study enlisted 102 people aged 75 and over who had relatively low levels of omega-3 fatty acids. All the participants were generally healthy, with no dementia (measured by mini-mental state examination and MRI scans at the start), but had some degree of white matter lesions (common changes in the nerve cells of the brain in older people).

The researchers gave half the participants 1.65g of omega-3 in 3 soft gel capsules daily. They gave the control group 3 soft gels containing only soybean oil, which were identical in taste, appearance, smell and texture to the omega-3 capsules.

Neither the researchers nor the participants knew who was receiving which treatment.

At follow-up visits throughout the 3-year trial, the researchers measured the development of white matter lesions in all the participants by MRI scan, and assessed cognitive function.

Positive effects only in people with APOEε4 gene

All participants tolerated the treatment well, with no severe adverse effects caused by the treatment.

In the whole group, the researchers found no significant difference in outcome between those on the omega-3 treatment and those on placebo. However, for those with the APOEε4 gene, there was a significant difference in the progression of white matter lesions between the groups.

People with the APOEε4 allele in the omega-3 group had significantly less nerve cell breakdown than those with the allele in the placebo group.

Allder explained how the fish oils might have this effect:

“Carriers of the APOEε4 gene have a higher risk of developing Alzheimer’s disease and may have a different metabolic or inflammatory response to [Omega-3] PUFAs compared to non-carriers. This gene is associated with increased brain inflammation and oxidative stress, which [Omega-3] PUFAs are known to mitigate.”

“The specific genetic and biochemical environment in APOEε4 carriers might make them more responsive to the neuroprotective effects of [Omega-3] PUFAs, thus leading to the observed reduction in neuronal integrity breakdown.”
— Steve Allder, MD

Fish oil may be a potential preventive treatment for some

The authors of the study do not advise the use of fish oil supplements by all older people, but suggest they may help reduce Alzheimer’s risk in those who have the APOEε4 allele. However, they emphasize that this was a small study, and that further clinical trials are needed to verify their findings.

Senior co-author of the study, Lynne Shinto, ND, MPH , professor of neurology, OHSU School of Medicine, commented in a news release:

“Our findings showed that over three years, there was not a statistically significant difference between placebo and the group that took fish oil.”

“I don’t think it would be harmful, but I wouldn’t say you need to take fish oil to prevent dementia,” she advised.

Both Allder and Molly Rapozo, RDN, registered dietician nutritionist and senior nutrition and health educator at Pacific Neuroscience Institute in Santa Monica, CA, told MNT that fish oils are generally safe, but people should take them only under medical advice.

“Contraindications are always a concern and I recommend clients speak with their medical team before adding supplements. Though generally safe, there are age- and dose-dependent effects, especially for those with 2 copies of the APOE4 gene,” Rapozo told MNT.

She added that it is preferable to increase the omega 3 in your diet: “In the meantime, up your intake of small cold-water fish which are good sources of omega 3 fats,” she advised.

Larger studies needed

While recognizing that these are interesting findings, both Allder and Rapozo stressed the need for more studies:

Allder advised that: “Further research should include larger and more diverse sample sizes to confirm these findings and determine the generalizability of the results. Studies should also investigate the long-term effects of [Omega-3] PUFAs on cognitive function and brain health, as well as the optimal dosage and formulation of fish oil supplements.”

Rapozo echoed this advice, and suggested altering the dosages of omega 3 to further assess their effects:

“Large-scale and long-term randomized controlled trials would certainly be beneficial. I’d also like to see an increase in dosage from the 1.65 grams provided in this study. 2-4 grams of EPA and DHA is considered a therapeutic dose to optimize fatty acids and lower triglyceride levels.”

“We’ve seen this dose show benefits in conditions associated with chronic inflammation, such as cardiovascular disease and rheumatoid arthritis. With 2 or more grams per day, we may see a more significant effect,” she added.