Many people take fish oil capsules because they have heard that omega-3 fatty acids are good for the brain.
Since Alzheimer’s disease has no cure, it is understandable that people hope a simple supplement might lower their risk.
A new study from Keck Medicine of USC, however, found that fish oil supplements did not provide the brain protection many people expected, even though the nutrients successfully entered the brain.
Omega-3 fatty acids, especially DHA, are essential nutrients that help build healthy brain cell membranes and support communication between nerve cells. Because fish naturally contains high levels of DHA, scientists have long wondered whether taking fish oil supplements could slow brain aging or prevent Alzheimer’s disease.
To investigate, researchers enrolled 365 adults aged 55 to 80 who ate very little fish. These volunteers were considered to have a higher risk of Alzheimer’s disease, and almost half carried the APOE4 gene, which greatly increases the likelihood of developing the condition later in life.
For two years, participants took either a high-dose DHA supplement or an inactive placebo tablet. Throughout the study, researchers measured memory, thinking ability, and changes inside the brain. They also measured DHA in the fluid surrounding the brain to confirm that the supplement reached its target.
The results answered one important question. DHA clearly entered the brain, with levels rising by an average of 17 percent after six months. Unfortunately, that increase did not produce measurable improvements. People taking fish oil scored similarly to those taking placebo on cognitive tests, and brain scans showed no difference in shrinkage of the hippocampus.
These findings suggest that preventing Alzheimer’s disease is much more complicated than increasing a single nutrient.
The researchers believe that the body may use omega-3 fatty acids more effectively when they come from an overall healthy eating pattern, such as the Mediterranean diet, instead of from supplements alone. Other factors, including age, genetics, overall health, and diet, may also influence how the brain responds to omega-3s.
Although the results may disappoint people hoping for a simple solution, they also provide valuable scientific evidence. Knowing what does not work helps researchers focus on more promising strategies.
The study reinforces current medical advice that maintaining overall health through exercise, nutritious eating, good sleep, controlling chronic diseases, and avoiding smoking remains the most reliable way to support brain health as people age.
The study was published in the journal eBioMedicine. This was a well-designed randomized, double-blind, placebo-controlled clinical trial involving 365 older adults at increased risk of Alzheimer’s disease.
The researchers confirmed that DHA from fish oil reached the brain, making the findings particularly important because the lack of benefit was not due to poor absorption. However, the study focused on older adults who rarely ate fish and were already at higher risk of Alzheimer’s, so the results may not apply to younger or healthier people.
The study also tested a fish oil supplement rather than a diet naturally rich in omega-3 foods. Overall, the findings suggest that fish oil supplements alone are unlikely to prevent Alzheimer’s disease, while a healthy lifestyle and balanced diet remain the strongest evidence-based approaches for supporting brain health.
If you care about Alzheimer’s disease, please read studies about the protective power of dietary antioxidants against Alzheimer’s, and eating habits linked to higher Alzheimer’s risk.
For more health information, please see recent studies that oral cannabis extract may help reduce Alzheimer’s symptoms, and Vitamin E may help prevent Parkinson’s disease.
