Silicon Valley has turned vitamins and supplements into a form of longevity theater, but the evidence for daily multivitamins in healthy adults is far weaker than the hype suggests. The strongest case for supplements is targeted use of B12 for vegans and some vegetarians, vitamin D for people at higher risk of low levels, and fish oil for filling meaningful omega-3 gaps. Vitamin supplements are most useful when they address a real nutritional shortfall rather than a vague hope of longer life.