Vitamin C (ascorbic acid) helps prevent colds

False. However, several well-designed studies have shown that when one gets a cold the symptoms may be lessened if vitamin C is being taken when the cold starts. Thus one has to weigh up the nuisance and risk of taking large doses of vitamin C (500 milligrams or more per day) for extended periods of time against the respects of reduced cold symptoms. The risks of excessive vitamin C intake include an increased intake of sodium (if it comes as sodium ascorbate), increased and excessive ingestion of iron with damage to tissues, and diarrhoea ( see Large Dose of Vitamin C can cause Diarrhoea). It is our personal view that the benefit is not worth the risk.