C-1500 Timed Release 250 TabletsDietary Supplement With Rose Hips Immune System Support Vitamin C, also referred to as ascorbic acid, is the single most commonly used vitamin supplement. It plays a major role in the formation of collagen (a structural protein in connective tissue), amino acid metabolism and hormone synthesis, and the utilization of many nutrients, such as folic acid and iron. It is also a key factor in the body's immune system.