Your body does need a multi-vitamin, and a anti-oxidant.
Most the vitamins that we eat from foods are passed directly through our bodies. Also with the increase in hormones, and pesticides on our vegtables, and fruits, the vitamins that were once filled in our foods are now non-existant and potentially hazardous to us as well.
That's why you need a vitamin, we definitely don't get enough no matter how much we eat.. unless you can shell out the $$ for mostly all organic foods. That's always the best.
Now as far as an anti-oxident. Our body is exposed to tons of nasty toxins in the air, and by the way we eat, drink etc. Pretend you have an apple, and you leave the apple out.. the air turns it brown right? That's how our skin is, and our bodies are.. in order to keep it from aging quickly and getting sick quickly, we need the anti-oxidants.. Red fruits, spinach & green leavy vegtables will help with that too.. but just take the pill or some juice that is high in it.