Indeed. I had heard that as well, though I don't know the validity of it. What I have seen, however, is dangerously low/high amounts of whatever is said to be in the vitamins.
In any event, just be careful about the amount of any particular vitamin you get. Excess vitamin A is a lot different than excess vitamin C (In the harmful dosages, and its effects of course)
LD50 for Vitamin C is 11900mg/kg
LD50 for Vitamin A is 1510mg/kg