the boys have whatever they're into! At the moment it's round lettuce, it used to be Cos. I guess they know about the credit crunch... clever pigs!
My pigs have always had lettuce. The 3 I had when I was a kid lived to 8 1/2, 6 and nearly 7 and they had Chicoree every day of their lives.. The first one actually literallly helped herself in the fridge (or nearly...) and the last one would eat my mum's fresh lettuces from the market if they were left in the basket on the floor overnight as she was free-roaming in the kitchen (she was a cheeky madam - the pig not my Mum! mallethead).
The boys love their carrots at the moment and their green beans too (only extra fine, though... snobs!). All my piggies have always loved Locust beans, which again is supposed to be bad for them, but, see above...
I think foods should come with a warning that they MAY cause such and such issues, but not necessarily and only experience will tell. Not all humans have deadly allergies to nuts but nuts MAY cause allergies... I should know with the gazillion I ate today... I'm still alive, no rash to declare, I'm not vomitting is a pyrotechnic fashion...
So if my boys like something, they can have it, that's my philosophy. I hear red pepper is good for them, well, I can't convince them, sorry

I have reduced their parsley intake, partly because of what I read on here but also becuase they've gone off it...