It has been argued that cat food with rice affects taurine matabolism. Taurine is vital to cats and a lack of it in the diet can cause DCM (heart disease with dilated heart walls) and eye damage (retinal degeneration).
|Taurine deficiency. Chart in public domain.|
Once you have studied cat food you realise that things are not what they seem. I continue to be surprised to see such ingredients as peas (you can see them in the cat food) in sachets of say, prawns in jelly. And rice is commonly added to cat food.
I'd read the packet carefully. A study by The American Society for Nutritional Sciences (carried out in 2002, a long time ago and having little effect it would seem on the pet food manufacturers) states that "dietary rice" decreases the amount of taurine in "whole blood" and "plasma". I think that this is the article: Dietary Rice Bran Decreases Plasma and Whole-Blood Taurine in Cats.
The research article says that despite the fact that manufacturers supplement cat food with taurine, cats are still being diagnosed with a deficiency of taurine. They put this down in part to the presence of rice in the cat food. The presence of rice naturally affects the content of fat, pr0tein and fiber (proper cat food), which in turn could affect the metabolism of taurine.
There is also the issue of intestinal bacteria, which could be altered by the presence of rice. This can cause an increase in the degradation of fecal bile acids, which in turn leads to loss of taurine in the feces.
Conclusion: This is difficult, but the more I read about cat food the greater the need to read the packet and find the best. The best is raw, home made with the right supplements. In lieu of that high quality wet cat food without rice could be a good start.
See Homemade Cat Food (as described by Bengal Cat Breeders).