Whole food vitamins work better because they are accompanied by other co-vitamin helpers and synergistic components. Below is an excerpt about the effects of natural and synthetic vitamins from drheise.com that may help you.

The marketing of fractionated crystalline synthetic vitamins has been so successful that most nutritionists and doctors are unaware that there is something missing from these “vitamins.” Vitamin manufacturers compete for customers with identical products – they all bought their synthetic vitamins from the same couple of drug companies. To differentiate their product, each makes claims of “high potency.” Our vitamins are higher potency than theirs, etc. The point is, the higher the potency, the more the druglike effects are present.

Natural whole food vitamins are very low potency. Remember the 20mg of vitamin C in a potato that was able to cure a patient of scurvy? That was low potency. Low potency is all we need. Low potency is enough to bring about vitamin activity. High potency overshoots the mark – the chemical is very pure and refined, like the difference between white sugar and the type of sugar that’s in an apple.