Does anybody know if this is okay? I've read that you're not supposed to microwave formula or breast milk (for reasons I'm still not sure of...

so I just always heat bottles in a pan of hot water). I just started giving my ds (who is just over 5 months old) veggies (that come in the jars), and have been heating them by placing his little bowl into a bigger bowl that has hot water in it (same idea as with his bottles). But is it ok to microwave it? Thanks!
Whiskers