Gluten

Mmm. Gluten! I love it, but all my friends think there's something advantageous to avoiding it. I'm pretty sure none of them have celiac disease (that's not common, is it?) So WTF?

Unless your friends have Celiac, if they are claiming a gluten allergy you can call bullshit. There was a recent fad which blamed the world of problems on gluten, but actual scientific research has demonstrated it to be false (unless of course you have Celiac). You can always find people who will say "I immediately lost 50 pounds and my skin and hair are healthier and my bowels became regular and all of a sudden I could run a marathon in record breaking time all because I stopped eating gluten/dairy/red meat/chocolate/etc" but the placebo effect is strong indeed, my friend, and just because some celebrity says so doesn't make it true.