I tried a vegetarian diet years ago and I never felt worse or had less energy in my life. I discovered something about myself that I had not know before. My body needs protein, more protein than most people, to function properly.
I would’t doubt it .. I don’t think diets or any medical treatments are a one size fits all...
My dad became a vegan after surviving prostate cancer at age 72... his PSA scores have never been as low as they are now. It may be an age thing...perhaps once your’re over 50 you don’t need as much protein.