My mother is 73 years old and does not know whether to consume EPA or DHA to try and retain her mental capacity?

While few studies have been conducted,there is population data to suggest that a few servings of fish per week (having more DHA than EPA) may hep to slow down the deterioration in cognitive performance with aging. A very recent study in aging seniors found some apparent benefit in their maintaining better mental performance with supplementation at 900 mg DHA/day on top of their regular diet.