My opinion of hierarchy of best doctors for health and longevity with vitality. This is based on their world-class research and proven results.
Dr Roy Walford MD (born 6/29/24, died 4/27/2004 at 79 of ALS) videos
Dr. Greger's key videos:
https://nutritionfacts.org/video/how-doctors-responded-to-being-named-a-leading-killer/
However, he only reports on subjects covered in the medical literature. So if you have a problem common/attractive enough to get written up in the literature, he can speak to it. Many subjects go outside of this limited set of data.