Is Zinc a Miracle Drug?

Chris Hayes tweets:

11:10 am: Honest question: is there some trick for people who fly all the time to not constantly get sick? 

11:23 am: Lots of votes for airborne and zinc.

Forget Airborne. Let’s talk about zinc. Every instinct in my body tells me it doesn’t work. It’s a scam. There’s no double-blind evidence for it. Etc. But I use the nasal spray version of Zicam and….it seems to work! Even though I’m really skeptical about it, which ought to wipe out any possible placebo effect. Unless I secretly do believe it in the lizard part of my brain responsible for such things.

Or maybe I just think it works because I’ve never kept serious track of how I respond. Who knows? Thus, today’s question: do you use zinc for colds? Does it seem to work? And why aren’t there any good clinical studies of it? You’d think some academic type would be curious enough about it to get a small NIH grant or something and check it out. Anybody know of some academic type who’s done this?