Several years ago, dry cat foods were linked to the cause of urinary problems in cats, especially males. There were multitudes of incidences occurring everywhere. The high ash content in dry food, which is the minerals like calcium, phosphorus, potassium, magnesium and other minerals, was causing crystals to form in the urinary tract. The specific culprit was the mineral magnesium. Cat food manufactures modified the formulations of dry food to lower magnesium. I remember that the premium cat foods were the first to modify, making them extremely popular. Now most of the dry cat food is modified. There should be less than 230mg of magnesium per serving. The magnesium level is listed on the labels of all good quality food.
Can foods are about 78% water. Cats have a tendency of not drinking enough water so wet food is a good alternative at providing the necessary amount of water your kitty needs. Cats tend to drink more water if the water bowl is NOT next to the food bowl. Try it, my cats seem very amused with the water bowls located away from the food. Can food may also provide the extra nutrition that cats need. Many commercial dry foods are packed with carbohydrate fillers like corn or corn meal. It is also a matter of convenience. Dry food is very convenient verses wet food. It is also a matter of what you cat prefers.
I feed my cats both. I have dry food in a bowl for them all the time. Between my four cats, I feed them 2-3 servings of 3oz can food that they share. They eat the wet food and munch a little on the dry cat food throughout the day. None of my cats have developed obesity or other illnesses that can be associated with eating dry food too long. Dry food has contributed to the following health diseases: feline diabetes, inflammatory bowel disease, chronic renal failure, urinary crystals, diarrhea, and dehydration. If you feed your cats dry food I do suggest feeding them one of higher quality. I have always feed my cats Hills Science Diet, and my cats and I have been very happy with that brand.
Avoid dry food that has coloring added. Some dyes are added to cat food to make them more appealing to humans. You will see this more in generic and supermarket brand cat foods. Most premium brands like IAM’s do not add dyes to the food. Choose instead the unappealing (to our eye) uncolored food that at least will not leave a permanent red or green stain on your carpet when your kitty eats too much too fast and upchucks.