By "learn", I assume you mean read existing literature on the topic

Also around the topic, not to mention that learning necessarily involves a fair amount of one's own thinking.

high-quality literature is rather sparse

I agree which makes relying of authority (and, usually, on mass media reinterpretations of authority) particularly suspect.

what's up with that?

I think the usual explanation is privacy and medical ethics, but my cynical mind readily suggests that it's much harder to critique a study if you can't see the data...