This made me think of Pauling (https://en.wikipedia.org/wiki/Linus_Pauling) who was a famous scientist and big proponent of high-dosage C-vitamin. He claimed it could cure everything from a cold to heart disease and cancer. Later studies did though not find any benefit of high-dosage C-vitamin and that potentially had a higher risk of prostate cancer. Pauling died of prostate cancer.

Edit: This may also be of interest: https://en.wikipedia.org/wiki/Orthomolecular_psychiatry