Vitamin C, or ascorbic acid, is a lactone and co-enzyme that is synthesized by all plants and animals, except for humans, apes, guinea pigs, and some bat populations. Vitamin C is necessary for important physiological functions, the most important being the formation of and maintenance of collagen in the connective tissues that make up bones, capillaries, gums, and teeth. Since humans cannot produce Vitamin C, it must be obtained from dietary sources like citrus fruits, berries, melons, potatoes and vegetables. A diet that is deficient of Vitamin C impairs the production of collagen and causes pain in the joints, anemia, nervousness, stunted growth, and reduced immune response and in a most extreme case, scurvy. The RDA recommended dosage of Vitamin C is 60 mg a day, while over 1000 mg per day is considered a megadose. Although the megadose amount ensures that a sufficient amount of ascorbic acid is available in the body, it can also be harmful.