Getting enough vitamin B-12 is always important, but especially so if you think you may be at risk for Alzheimer’s disease.

When 187 adults who carried the gene were recently tested, those with low B-12 levels performed significantly worse on memory tests than those with healthy levels. None of the subjects actually had Alzheimer’s disease, but the results suggest that a diet high in B-12 may help ward it off.

Though most people will never know for sure if they carry the gene, family history is a strong indicator. And while most Americans do get enough B-12 from their diets, many develop a deficiency around age 50 because of problems absorbing the vitamin from foods. Vegans are also at risk since B-12 is found mainly in animal products like fish, meat, and dairy.

The best way to stock up? Supplements or fortified foods like breakfast cereal and soy foods.