Linus Pauling won two Nobel Prizes and then spent the end of his career insisting that very high doses of vitamin C could help people with cancer. Two large Mayo Clinic trials tested the idea, found no benefit, and the matter was widely considered closed.
There is a detail in that history that neither the trials' defenders nor their critics emphasized at the time. Pauling and his collaborator, the Scottish physician Ewan Cameron, started their patients on intravenous vitamin C and only later switched to tablets. The Mayo trials used tablets only.
