I depends on what your friend is feeding his cat with. If the cat looks and acts healthy (no other symptoms to indicate an illness) maybe giving the cat some wet food too or something like a soup might help for a better digestion.
I had a cat with chronic constipation, and his stools were very hard and uncomfortable for him to pass. The vet suggested putting either Benefiber or Fiber Sure in his wet food and diluting it with water. Start out with 1/2 teaspoon twice a day. It worked very well for him. Hope it works for your friend's cat.
P.S. I used Fiber Sure because it has a higher fiber content.