The easiest way to think of vitamins is to think about food.
Vitamins are concentrated food products.
So you get more Vitamin C in a 1000mg capsule than you do in a couple glasses of orange juice or from several oranges.
Different Vitamins and Minerals have different effects in the body. think of them as co-factors. They can often expedite biochemical functions.
The debate ranges between the people that claim that you do/can get all the nutrients you need from a reasonably standard American Cuisine, and the belief that extra supplementation will give an added bonus.
IS more better?
It would make sense that a serious athlete would need much more nutrients than a couch potato.
Or that someone recovering from an illness may have special needs.
And there have been some pretty compelling studies to show that at least at certain times and under certain conditions vitamins can make a big difference.
I take mine on faith
.