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:

SYMHC Classics: COINTELPRO 1
39:12

Behind the Scenes Minis: It's Not Unprecedented
16:46

The Rendition of Anthony Burns, Part 2
43:32