They always forget a few other factors. Calciferol, ivermectin, and others
This is not a valid study and these doctors are shams and should know better.
I’ve seen so many studies where they intentionally sabotage the result. Let’s say potatoes contain a factor that will inhibit the effectiveness of the thing being tested. And golly gee, guess what each Guinea pig gets served each day of the trial? POTATOES.