Researchers at Keck Medicine of the University of Southern California tested whether daily fish oil supplements could protect brain health. Their two-year trial involved 365 adults aged 55 to 80 who rarely ate fish and had an increased risk of Alzheimer's disease. Participants were randomly assigned either fish oil containing 2,000 milligrams of DHA each day or a placebo, a treatment with no active ingredient. Neither the participants nor the researchers knew which treatment each person received.
DHA is an omega-3 fat that supports the structure of brain cells and communication between them. After six months, its level in the fluid surrounding the brain and spinal cord had risen by an average of 17% in the supplement group. However, after two years, people taking fish oil performed no better on memory and thinking tests than those taking the placebo. The supplements also failed to prevent shrinkage of the hippocampus, a brain region important for memory.
The findings do not mean that omega-3 fats are unnecessary or that eating fish has no health benefits. Rather, high-dose DHA supplements alone offered no measurable brain protection in this group. The researchers are investigating how the brain processes these nutrients. They recommend regular exercise, good-quality sleep and a balanced diet, rather than depending on a single supplement.
