In general, the healthcare profession could do the same double-blind studies they do on drugs -- but on substances that are not patentable, such as vitamins, minerals, fruits, vegetables, natural herbs and plants, etc.
They could even do double-blind studies on things that are not ingestable, like sunlight, doing enough exercise, getting enough rest, etc., etc.
But will they, ever?
No they will not.
That's because they will not make any money if these studies are successful.
Quite the opposite.
If there is any successful study in one or more of these areas, it could very well have negative and damaging economic impact to the medical community.
I like Doctors, and believe that most of them are good, honest, decent, hard-working (especially now, during CoronaVirus!) people.
They are not the enemy, quite the opposite!
But we really need to think about double-blind studies on non-patentable things that could potentially cure people, or at least alleviate their condition in some small way.
That, and the FDA needs to allow those things as treatments that Doctors may legally prescribe, if the double-blind studies prove successful...