Vitamin C also referred to as ascorbic acid, is the single most commonly used vitamin supplement. Vitamin c, also referred to as ascorbic acid, is the single most commonly used vitamin supplement. Vitamin C 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. Vitamin C is also a key factor in the body's immune system. Source Naturals c-1000 provides a gradual release over a prolonged period of time.