Vitamin C (also known as ascorbic acid) is an important nutrient which must be obtained from the diet or by supplementation, as it cannot be synthesized by the human body. Major dietary sources of vitamin C are green vegetables and fruit. Vitamin C is one of the most labile dietary nutrients, being easily destroyed by cooking or food processing. Levels of vitamin C are reduced by smoking, drinking alcohol, as well as by certain drugs (e.g. anticoagulants, antidepressants, oral contraceptives).