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

Katharine Lang

• 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, speaking 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