Grains are harvested in large quantities and in many countries represent the main food in the diet of animal and human populations. In almost all countries of the world, the consumption of grain is present in substantial quantities in the various diets. Rich in starch, grains are characterized by the high digestibility and ease maintenance, which has contributed to their wide dissemination. The cultivation is often intensive, on large surfaces, made easy by the use of machinery, both for the sowing, for the treatments and for the harvest.
Grains provide the bulk of their energy and nutrient such as starch and are also important sources of protein. Whole grains (grains which retain the bran and germ) are rich in fiber, fatty acids and more. Grains are a source of energy (about 350 kcal per 100 g), typically low in protein, except for rice, whose proteins are rich in lysine, which is considered the best among the proteins of grains. The rice is a source of vitamin B, but low in calcium and iron.