protein added, a wheat-based meal is highly nutritious. [ 49 ] The most common forms of wheat are white and red wheat. However, other natural forms of wheat exist. For example, in the highlands of Ethiopia grows purple wheat, a tetraploid species of wheat that is rich in anti-oxidants. Other commercially minor but nutritionally promising species of naturally evolved wheat species include black, yellow and blue wheat. [ 4 ] [ 50 ] [ 51 ] The following table shows the nutrient content of wheat and other major staple foods in a raw form. [ 56 ] Raw forms of these staples, however, are not edible and cannot be digested. These must be sprouted, or prepared and cooked as appropriate for human consumption. In sprouted or cooked form, the relative nutritional and anti-nutritional contents of each of these grains is remarkably different from that of raw form of these grains reported in this table. Harvested wheat grain that enters trade is classified according to grain properties for the purposes of the commodity markets . Wheat buyers use these to decide which wheat to buy, as each class has special uses, and producers use them to decide which classes of wheat will be most profitable to cultivate. Wheat is widely cultivated as a cash crop because it produces a good yield per unit area, grows well in a temperate climate even with a moderately short growing season , and yields a versatile, high-quality flour that is widely used in baking .