By Juliana Weiss-Roessler Do you take a daily multivitamin? You may wonder if your dog can benefit from one as well. In fact, some estimates say that around one third of dogs receive supplements. Why Dogs Need Vitamins Much like in humans, vitamins help a dog’s body to function properly, regulating everything from digestion to muscle growth. They’re crucial to maintaining your dog’s health, and a deficiency of a particular vitamin can cause health problems, which can sometimes have serious and long-lasting effects. But here’s the good news: most pups are probably getting what they need from their dog food.