Some scientists think that taking omega-3 supplements might hurt memory or thinking in older people because these fats can break down in a way that damages the energy supply in brain cells.

When older adults with memory problems eat more omega-3 fats from fish or supplements, their bodies show less of a type of cell damage linked to aging and brain decline.

Taking omega-3 supplements might be linked to a faster drop in brain energy use in areas affected by Alzheimer’s, and this could explain up to 40% of why some older adults’ memories and thinking skills get worse over time.

For older adults with mild memory problems, having high levels of omega-3s in the blood might help slow brain shrinkage—but only if they’re also taking B vitamins. Alone, omega-3s don’t seem to help.

Omega-3s might help slow brain shrinkage in older people with memory problems, but only if they also have enough B vitamins—without enough B vitamins, omega-3s might not help at all.

For older people with early memory problems, taking omega-3 supplements might make their memory and thinking skills get worse faster over five years, which is the opposite of what most people think.