Humans depend heavily on three crops for food: wheat, rice, and corn. As whole grains, these crops, if they were the sole source of food, would provide adequate amounts of protein, carbohydrate, and fat. However, they lack certain amino acids, vitamins, and minerals. This means the diet needs to be supplemented with fruits and vegetables. Meat, dairy products and fish can also supply some of these nutrients as well as being additional sources of protein.