Why does everyone and their uncle still think Vitamin C can cure cancer, leprosy, and gout? One man: Linus Pauling. The guy was a veritable genius for a portion of his career, and he won two different Nobel Prizes all on his own. It's just that one day, another doctor who had gotten his PhD from an unaccredited correspondence school told him that 3,000 mg of Vitamin C a day would make him live another 25 years, and he bought it. He bought it so hard that he wrote books about it telling everyone else to do it while he was up to 18,000 mg a day. That is some "sell the cow to a maniac in exchange for some magic beans" shit.
The face of a man doing 300 times the "required" dose.
The daily requirement of vitamin C needed to ward off scurvy is 60 mg. Fortunately, water soluble as vitamin C is, if you take an excess, you'll piss it away and no harm done. Generally speaking. But that "no harm done" upper threshold maxes out at around 2,000 mg a day. Mega doses can and will cause side effects like diarrhea, kidney stones, heart burn, cramping, and vomiting. Pauling must have thought those were just his body's way of celebrating its newfound health.