Any food made from wheat, rice, oats, cornmeal, barley or another cereal grain is a grain product. Grains are divided into 2 subgroups, whole grains and refined grains. Whole grains contain the entire grain kernel -- the bran, germ, and endosperm. Refined grains have been milled, a process that removes the bran and germ -- and removes dietary fiber, iron, and many B vitamins. Popcorn, bread, pasta, oatmeal, breakfast cereals, tortillas, and grits are examples of grain products. The USDA recommends six ounce equivalents of grains with at least three of those coming from whole grains. In general, 3 cups of popcorn, 1 slice of bread, 1 cup of ready-to-eat cereal, or 1/2 cup of cooked rice, cooked pasta, or cooked cereal can be considered as 1 ounce equivalent from the grains group. Popcorn is a starch exchange recommended by the American Diabetes Association and the American Dietetic Association.