L-ergothionine has been around for a long time but no one really has any idea what if any role it plays in human metabolism. People with rheumatoid arthritis have a mutant L-ergothionine transporter that more efficiently takes it up and so have higher levels in the blood but whether or not the increased L-ergothinine plays a role in the development of rheumatoid arthritis is unclear. It certainly makes no sense to take it as a supplement as far I know.James J. Kenney, PhD, FACN