If you're an older adult with early memory problems and you take B vitamins, having more omega-3s in your body from the start might help slow down brain shrinkage—but only if you're taking the B vitamins, not a placebo.

We analyzed the available evidence and found that among older adults with mild cognitive impairment, the combination of B vitamins and higher levels of omega-3 fatty acids may be linked to a slower rate of brain shrinkage—but only when B vitamins are taken, not a placebo [1]. The evidence we’ve reviewed so far leans toward the idea that omega-3s alone don’t appear to have this effect without B vitamins present. What we’ve found suggests that the presence of omega-3s in the body before starting B vitamin supplementation might help enhance the impact of those vitamins on brain structure. This doesn’t mean omega-3s cause brain protection, or that B vitamins work the same for everyone. It simply points to a possible interaction between the two, based on the one assertion we’ve reviewed. We don’t yet know how much omega-3 is needed, how long someone must take B vitamins, or whether this effect holds for people without early memory issues. The evidence is limited to a single assertion, and no studies contradict this finding—but that doesn’t mean it’s true for all older adults. More research is needed to understand who might benefit, and under what conditions. For now, if you’re an older adult with early memory concerns and your doctor recommends B vitamins, having a diet or supplement routine that includes omega-3s might be worth considering—but always talk to a healthcare provider before making changes.