Why is America called Uncle Sam?

Milk contains proteins essential for building and repairing muscles. It also has fat which gives energy. This fat is called butterfat. Then there is sugar, a carbohydrate which gives energy. The milk in sugar is called lactose. Milk also has many minerals that help to build bones and blood. It is rich in calcium and phosphorus. It also has many vitamins —B2, A, B 1, C and D.