In 1989, David Bailey, a researcher in the field of clinical pharmacology (the study of how drugs affect humans), accidentally stumbled on perhaps the biggest discovery of his career, in his lab in London, Ontario.
https://www.atlasobscura.com/articles/grapefruit-history-and-drug-interactions
https://www.atlasobscura.com/articles/grapefruit-history-and-drug-interactions