Specialists keep up with the latest research in their domains and talk with other specialists in their field. They usually know about these things before their patients discover them spontaneously.

You can read a lot of published papers on PubMed by searching for a condition or drug. You should be aware that there are a lot of papers published that say disease A can be treated with drug or supplement B that fail to replicate if anyone else tries it. It takes some practice to recognize when a treatment represents a real trend as opposed to a single quack doctor looking for a status boosting publication with some questionable claims.