Here's why:
* Lactose intolerance: As cats grow older, they lose the ability to digest lactose, the sugar in milk. Drinking cow's milk can cause diarrhea, gas, and stomach upset.
* Nutritional needs: Cow's milk doesn't provide the necessary nutrients for adult cats. They need a diet specifically formulated for their needs.
So, while kittens benefit from a small amount of milk, adult cats usually don't. If you're concerned about your cat's diet, consult your vet.