Multivitamins cause an increase in blood concentrations of the vitamins and metals contained theirin. Their absorption has been shown to be lesser than that of the same amount of the compounds contained in actual food. That said, you have to be cognisent in your choices of specific fruits and vegetables to ensure you are obtaining the complete set of essential vitamins and metals. Multivitamin supplementation does not improve the health of those with a complete diet, it does however have positive effects when a diet is lacking in one thing or another. Why do you think people with osteopenia or osteoporosis are encouraged to supplement with vitamin D by their physicians? It's because vitamin supplements do in fact have an effect, it's just not the same as it would be with a food based source.