Fish oil supplements are among the most popular health products in the world. Every year, people spend billions of dollars hoping these capsules will protect their hearts, joints, and especially their brains.
Much of this interest comes from omega-3 fatty acids, important nutrients found in oily fish such as salmon, sardines, and mackerel. These healthy fats help build brain cells and support communication between nerve cells, leading many people to believe that taking fish oil every day can prevent memory loss and Alzheimer’s disease.
A new study from Keck Medicine of USC suggests the answer may not be so simple. Researchers found that although omega-3 supplements successfully reached the brain, they did not improve memory, thinking ability, or signs of brain aging in older adults who were at increased risk of Alzheimer’s disease.
The scientists followed 365 adults between 55 and 80 years of age in a carefully designed clinical trial that lasted two years. All participants rarely ate fish, making them good candidates for studying omega-3 supplements. Nearly half also carried the APOE4 gene, the strongest known genetic risk factor for late-onset Alzheimer’s disease.
Participants were randomly assigned to receive either a daily fish oil supplement containing 2,000 milligrams of DHA or a placebo. Neither the participants nor the researchers knew who received the real supplement until the study ended.
One important question was whether DHA from supplements could actually enter the brain. To answer this, researchers measured DHA levels in cerebrospinal fluid, the liquid surrounding the brain and spinal cord. After six months, DHA levels had increased by about 17 percent, proving the nutrient had reached the brain.
However, this did not translate into better brain health. After two years, people taking fish oil performed no better than the placebo group on tests of memory and thinking. Brain scans also showed no slowing of shrinkage in the hippocampus, an area important for learning and memory that is often affected early in Alzheimer’s disease.
The findings suggest that simply increasing omega-3 levels in the brain may not be enough to prevent Alzheimer’s disease. Researchers think the brain may need other healthy lifestyle factors to use these nutrients effectively.
Previous research has suggested that Mediterranean-style eating patterns, which naturally include fish, vegetables, fruit, whole grains, nuts, and olive oil, may offer greater protection than supplements alone.
The researchers emphasize that people should continue focusing on habits already known to support brain health, including regular exercise, quality sleep, controlling blood pressure and diabetes, eating a balanced diet, and staying mentally and socially active.
These lifestyle choices remain the strongest evidence-based ways to reduce the risk of dementia while scientists continue searching for new treatments.
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 nutrition, please read studies that whole grain foods could help increase longevity, and vitamin D supplements strongly reduce cancer death.
For more information about nutrition, please see recent studies about natural coconut sugar that could help reduce blood pressure and artery stiffness, and whey and soy protein may reduce inflammation in older people.
Source: Keck Medicine of USC.
