On the whole, western diets provide all the vitamins you need. Vitamin D can be an exception, as its good food sources aren't that numerous and many of which are frequently avoided by veggies and vegans. Get thee almost naked into the summer sun is a partial solution. It's much more fun if you don't do it alone. Down, girls... Hardly anyone needs extra vitamin C. It's in most fresh plant foods. Onions contain even more than oranges and it's there in all your greens. Folic acid can be an issue for people who live on junk food. Otherwise, the supplement industry should be right there on the shelf with snake oil.