Methylmalonic acid and cognitive function in the Medical Research Council Cognitive Function and Aging Study
Many moons again, family docs use to give out B12 shots liberally. Inexpensive, safe and patient’s loved them. For some reason they dropped out of favor. Maybe because of the misguided notion that food fortification would give us all we need, much like Vit D? Unfortunately, as we age and with chronic stress, digestion suffers as well as absorption of Vit B12. Much higher dosages become needed to overcome the poor absorption.
Many studies put this level as >1,000 mcg/day. This study further confirms how important Vit B12 is needed for healthy brain aging.