Severe vitamin B-12 deficiency can cause irreversible neurological damage. In some people it can mimic dementia. But taking the vitamin doesn’t seem to prevent those problems who are only moderately deficient.

Brain scientists randomly assigned roughly 200 people aged 75 o older who had moderate vitamin B-12 deficiency to take either B-12 (1,000 micrograms a day) or a placebo. None of the people had anemia or symptoms of severe B-12 deficiency like tingling, numbness, difficulty walking, or memory loss.

After one year, those who got the B-12 do no better on memory or other cognitive tests and had no better nerve function than those who got the placebo.

What to do:    Anyone aged 50 or older should get B-12 (at least 2.4 mcg a day) from a multivitamin or fortified food (like cereal), in case a lack of stomach acid makes them unable to absorb the B-12 in foods (dairy, meat, poultry, and fish).

If you have symptoms of B-12 deficiency, get your blood levels tested.

Source: Nutrition Action Health Letter September 2015