The United States Institute of Medicine recommends against taking large doses. Large doses may cause gastrointestinal discomfort, headache, trouble sleeping, and flushing of the skin. It may be taken by mouth or by injection. It is unclear whether supplementation affects the risk of cancer, cardiovascular disease, or dementia. There is some evidence that regular use of supplements may reduce the duration of the common cold, but it does not appear to prevent infection. Most animals are able to synthesize their own vitamin C, although humans, the other great and lesser apes, monkeys (but not all primates), most bats, some rodents, and certain other animals must acquire it from dietary sources. It is required for the functioning of several enzymes and is important for immune system function. Vitamin C is an essential nutrient involved in the repair of tissue and the enzymatic production of certain neurotransmitters. Vitamin C (also known as ascorbic acid and ascorbate) is a vitamin found in various foods and sold as a dietary supplement.
