Yummy dirt..?

[Jilly]

My dog eats dirt... with relish! Seriously though, I really do want to know why he does this. He doesn't just occasionally sniff out some good smelling spot. He will stop, dig enough to clear away the grass, and then bite into it with his front teeth and eat it. Is he missing some trace mineral in his diet perhaps? He is on meds for congestive heart failure and water retention. He also takes Rimadyl for pain, as he has arthritis in his hips. I do give him Synovi G3 to help with that. SO with his taking those meds, it wouldn't surprise me to find that he is in need of some minerals or vitamins that he's not getting enough of now.
I do appreciate any insight about this. If it is a mineral deficiency I want to get the needed supplement for him as soon as possible.
Thanks so much,
Jilly