Do vitamins really work or are they a waste of money?

Mostly a waste: Most people get no benefit from a multivitamin. The supplement industry isn't under the same laws requiring truth-telling as real doctors. Vegetarians need to supplement, and vitamin d and iron deficiency are common depending on lifestyles. If you decide to take a supplement, choose a cheap drug-chain tablet; it should cost only a few dollars a year. The pricey ones are all scams.

Waste.: If you eat a regular healthy diet and have no identified vitamin deficiency then by and large vitamins are a big waste of both time and money. There is no evidence that supraphysiologic doses of vitamins is good for you either.