This episode on the pellagra epidemic focuses on its prevalence in the U.S. in the early 20th century. Some of the scientific work done to understand it involves self-experimentation, and some of it is ethically problematic by today’s standards.
Research:

Behind the Scenes Minis: Piece of Work
17:48

E. Virgil Neal: Hypnotist, Fraudster, Tycoon, Part 2
41:22

E. Virgil Neal: Hypnotist, Fraudster, Tycoon - Part 1
35:28