Although vitamin and mineral supplements are good to take in many instances, you cannot depend on pills alone to provide your body with the nutrients it needs. Approximately 150 phytochemicals are found in foods along with the vitamins and minerals the body needs. Phytochemicals play a very important role in helping the body defend itself against cancer and cancer-causing agents, and probably many other things as well. An example of a known phytochemical is beta-carotene, a carotenoid. It is found in deeply pigmented fruits and vegetables, such as carrots, sweet potatoes, tomatoes, spinach, broccoli, cantaloupe, pumpkin, and apricots.
Carotenoids act as antioxidants, reducing the risk of cancer.
Read Antioxidants for more info. Five servings a day is a great start. And if you supplement, don't megadose. More is not necessarily good for you. Besides being expensive, over-supplementing can be harmful to you, too.