Studies have shown for at least twenty years that a combination of vigorous daily exercise plus vigorous exercise of the brain - learning a new skill, not simply playing games or doing something you can already do - can push back dementia by a decade or more. But no one wants to exert themselves. Everyone wants a magic pill to absolve them from responsibility. This is the great appeal of supplements. That said, studies also show that magnesium supplementation can have a modest benefit for long-term memory function, and as most people are in general deficient across a wide range of micro-nutrients, sensible supplementation can help at the margins. But most supplements are empty nonsense designed to part the gullible and indolent from their money. And frankly, if people can't be bothered to make an effort to protect their health, why should we care if they waste their money on imaginary magic pills?