Cow's milk is naturally an excellent source of calcium. It has vitamin D and it has potassium and it's a complete protein source as well. With other forms of dairy – cheese, yogurt and other sources – you are getting some, but not all, of the nutrients from milk. For example, in yogurt the water in milk is taken away so you get possibly more protein per serving. But you may also get more fat and salt. Yogurt would be a good option to replace cow's milk if you'd like, especially a non-fat greek yogurt which is lower in carbs and higher in protein.