Kitten food is specially formulated with very high levels of protein, which is essential for proper growth, as well as higher levels of calcium, magnesium, phosphorous, zinc and iron to help build strong bones and teeth. The best food for kittens is one that's been formulated specifically for their age. Kitten food is specially formulated with very high levels of protein, which is essential for proper growth, as well as higher levels of calcium, magnesium, phosphorous, zinc and iron to help build strong bones and teeth. Kitten food also contains more vitamin C and vitamin E, which help support kittens' immune systems.