Vitamin C: Essential, Useful for Deficiency, and the Megadose Myth

Summary

Vitamin C is genuinely essential — humans cannot make it, deficiency causes scurvy, correcting real deficiency (smokers, alcohol-dependent, low-produce diets, malabsorption, dialysis) matters, and regular supplementation modestly shortens colds — yet the Linus Pauling megadose thesis that grams a day prevent or cure colds and cancer is wrong: the body saturates near 200 mg a day and excretes the rest, Cochrane finds no cold-prevention benefit in ordinary life (only a modest duration trim, plus a real prevention signal confined to extreme physical stress like marathoners and soldiers), the intr