For various medical reasons, I feed Cassie on Nature Diet alone. (Originally the vet specified tinned Chappie but after a month I simply couldn't face the smell.) She loves it and has had absolutely no ill-effects from it. But I too worry about the lack of 'crunch' and the effect on her teeth. So she gets lots of raw veg as well (mainly carrot, cabbage and broccoli) and I brush her teeth every other day.