I was told to keep mine on puppy food by PDSA's petcheck people until 18 months. Otherwise yes food quality is definitely important. The first bag of food I bought was a bit on the cheap side, he was hyper but I put that down to him. When I looked into the ingredients, I realised that all the pieces were shaped and coloured for human satisfaction and that it was mostly c**p! There doesn't appear to be the same regulation with pet food as with human food which probably explains the huge recall a few years ago.

Be careful with leftovers. Dogs are a great consumer of leftovers and if you're careful you can feed him only the best as a treat from his usual diet (not as a staple)