Vitamin C Powder (Reduced) 454 svg 1 lb by Metabolic MaintenanceThe need for additional Vitamin C (Ascorbic Acid) is increased during periods of emotional, psychological or physiological stress. During this time urinary excretion of Vitamin C is increased. The functions of Vitamin C in the human body are very diverse. It participates in the synthesis of collagen by hydroxylating proline to form hydroxyproline, the major protein from which connective tissue, cartilage, bone, skin, tendon and tooth dentin is made.