Anyone with kidney problems must not exceed 200 mg vitamin C intake daily because of hyperoxalemia risks. Vitamin C is the most widely known vitamin. It plays an essential role in the maintenance of the immune system, even during and after strenuous physical exercise. It is required for the production of collagen which reinforces connective tissue, muscles, blood vessels, teeth, bones and cartilage. Vitamin C also intervenes in the energy metabolism and the maintenance of the nervous system. It helps with the absorption of iron in the body. Vitamin C is a powerful antioxidant that acts in the regeneration of the reduced form of the vitamin E. Finally it helps with normal psychological functions.