If you're an older adult with mild memory problems, having more DHA (a type of omega-3 found in fish) in your blood might make B vitamins work better to help your brain, and DHA seems to help more than another omega-3 called EPA.

We analyzed the available evidence and found that higher levels of DHA in the blood may help B vitamins work more effectively for cognitive support in older adults with mild memory problems. The evidence we’ve reviewed so far leans toward this idea, with all 60.0 assertions supporting it and none contradicting it [1]. DHA, an omega-3 fatty acid found in fatty fish and algae, appears to play a stronger role than EPA, another omega-3, in this interaction. This doesn’t mean B vitamins alone don’t help, or that DHA alone is enough. Instead, the pattern we see suggests that when both are present — higher DHA levels along with B vitamin intake — there may be a combined effect on brain function in people experiencing early memory changes. We don’t know exactly how this works, but it could involve DHA helping brain cells respond better to the metabolic support B vitamins provide. It’s important to note that this is based on observations of blood levels and outcomes in studies, not on controlled experiments that prove cause and effect. We also don’t know the ideal amount of DHA needed, or whether taking supplements makes a difference compared to getting it from food. What we’ve found so far doesn’t tell us whether everyone with mild cognitive issues should increase DHA or take B vitamins. But if you’re an older adult with early memory concerns, and you’re already taking B vitamins, having enough DHA in your diet — through fish, algae, or supplements — might help those vitamins work better for your brain. Talk to your doctor before making changes to your routine.