It became famous as a brain protector, but a new study debunks the myth about Omega-3

Omega-3 supplements may not provide benefits for preventing Alzheimer’s

Evidence suggests that supplementation with the omega-3 fatty acid DHA does not appear to prevent memory loss or dementia. (Illustrative image: Domepitipat/GettyImages)

Docosahexaenoic acid (DHA) is an omega-3 fatty acid found in fish, but it can also be obtained through supplements that contain it.

Studies have produced mixed results regarding whether DHA helps cognitive function.

One study found that in adults without dementia and with low omega-3 intake, taking DHA supplements did not provide brain benefits, including in participants at high risk for Alzheimer’s disease.

People are constantly looking for ways to improve brain health and possibly prevent cognitive issues such as dementia.

One area of research interest is docosahexaenoic acid (DHA), an omega-3 fatty acid that can be obtained from fish or supplements.

A recent study published in *eBioMedicine* examined whether DHA supplementation provided cognitive benefits in people with low omega-3 intake.

Researchers found that although supplementation increased DHA levels, participants showed no improvement in brain changes or cognitive function. The findings suggest that DHA supplements alone may not help prevent dementia.

DHA and cognitive benefits

As highlighted in this study, people who carry the APOE ε4 have a higher genetic risk of developing Alzheimer’s disease. Individuals with this genetic status also tend to have lower DHA levels, while low DHA levels are also associated with late-onset Alzheimer’s disease.

The researchers of this study aimed to determine whether supplementation with high doses of DHA before the onset of dementia could be beneficial.

The study was a randomized, double-blind, single-center, phase 2 placebo-controlled clinical trial. Participants were aged 55 to 80 years and did not have dementia at baseline. They also had low dietary DHA intake and at least one risk factor for dementia or cardiovascular problems.

Participants received either a DHA supplement or a placebo for 2 years, with study visits every 6 months. Researchers assessed specific changes in the brain and also measured DHA levels in cerebrospinal fluid in some participants.

Exploratory outcomes included analyses of plasma biomarkers of Alzheimer’s disease and cognitive performance. Blood samples were also collected to measure fatty acid concentrations.

In total, 365 participants were randomly enrolled, and 225 completed the study. Researchers further divided participants into a group that underwent lumbar puncture to collect cerebrospinal fluid and a group that did not. Nearly half of the participants carried the APOE ε4 allele.

Compared to placebo, DHA supplementation appeared to increase DHA levels in cerebrospinal fluid after 6 months. This was true for both APOE ε4 carriers and non-carriers. In addition, DHA supplementation also increased DHA levels in the blood.

Although some brain changes were observed during the study, DHA supplementation did not show a significant overall effect.

Regarding cognitive function, DHA supplementation did not appear to improve outcomes, and this was consistent for both APOE ε4 carriers and non-carriers. Safety results were similar between the placebo and DHA groups.

So, although DHA reached the brain through supplementation, the results suggest it did not improve specific brain changes or cognitive function. The study’s author, Hussein N. Yassine, professor of Neurology, Medicine, and Physiology & Neuroscience at the Keck School of Medicine of USC, stated:

“The key finding of our research is that high-dose DHA, an omega-3 fatty acid, successfully reached the brain in older adults at risk for dementia… However, even though DHA reached the brain, we did not see improvements in memory, thinking ability, or brain structure over the 24-month study.”

Study limitations and further research

The study was detailed and included both placebo and intervention groups. However, it also had limitations. Mainly due to COVID-19, there was a 38% dropout rate, which may have influenced results, along with missing data that should be considered.

There are also limitations in generalizing the findings. For example, researchers note differences between participants who completed the study and those who did not, which may limit applicability to the broader population.

Misclassification is also possible. Some participants may have had cognitive issues that were not detected. Some data were also based on self-reports. One author also disclosed potential competing interests.

Researchers emphasize that their ability to detect true intervention effects may have been limited by factors such as the relatively young age of participants.

They also acknowledge that the study population “may not represent typical clinical prevention populations.” Focusing on a single nutrient also has inherent limitations.

Finally, the researchers note variability in measurements, as they used “lifestyle measures based on questionnaires, with broad criteria for cognitive inclusion.”

Long-term data and more detailed measurements may be useful going forward.

What can help prevent Alzheimer’s?

Overall, the results of this study suggest that taking DHA supplements does not benefit the brain. Yassine said:

“Our findings do not support the idea that people should take high-dose DHA supplements alone to prevent dementia.”

However, this does not mean omega-3 is unimportant. Yassine explained:

“Omega-3 remains an important part of a healthy diet. Foods rich in omega-3, such as fatty fish, support overall heart and brain health and should be encouraged as part of a balanced dietary pattern… In clinical practice, these results suggest we should focus less on single-supplement approaches and more on lifestyle strategies that support brain health.”

“This includes following a balanced diet that contains omega-3-rich foods, staying physically active, controlling blood pressure and cholesterol, getting good sleep, and managing other dementia risk factors.”

Dung Trinh, an internal medicine physician at MemorialCare Medical Group and medical director of the Healthy Brain Clinic in Irvine, California, who was not part of the study, also said:

“The supplement reached the brain, but did not improve brain outcomes. That distinction matters. The issue may not be brain penetration, but that Alzheimer’s risk is driven by multiple interacting mechanisms, including vascular disease, inflammation, insulin resistance, sleep disorders, lack of physical activity, hearing loss, depression, medication effects, and amyloid/tau biology.”

“The best strategy is a multi-domain approach to brain health, not a single supplement.”

Trinh added that this may include controlling vascular risk factors, physical activity, improving sleep, and early detection of cognitive problems.

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