There are many compelling reasons to eat grains such as corn, wheat, rice, oats, rye, millet, triticale, barley, amaranth, quinoa, and buckwheat. Such grains are rich in complex carbohydrates and provide both soluble fiber (the kind that lowers blood-cholesterol levels) and insoluble fiber (the kind that helps to prevent constipation and protects against some forms of cancer). People living in regions where unrefined whole grains make up a significant part of the diet are reported to have a lower incidence of intestinal and bowel problems than those who live in the industrialized countries of Europe and North America where fewer whole grains are consumed. Moreover, grains--especially whole grains--and grain products offer significant amounts of B vitamins (riboflavin, thiamine, and niacin), vitamin E, iron, zinc, calcium, selenium, and magnesium.
The kernels of grains are edible seeds which are composed of three parts--the bran, the endosperm, and the germ (or embryo). The bran is the outer covering of the kernel, which is rich in nutrients and provides most of the grain's dietary fiber. In some grains, such as wheat and corn, the fiber is essentially insoluble, while in other grains, such as oats and barley, it is mostly soluble. Whole grains contain the kernel's original bran, while the bran is usually missing from most refined grain products because it has been stripped away during the modern milling process.
The starchy endosperm accounts for most of the grain's weight. Most of the protein and carbohydrates are stored in the endosperm, as are some minerals and B vitamins (though less than are in the bran). The endosperm also has some dietary fiber, although less than in the bran. In wheat, the endosperm is the part of the grain used to make white flour.
The smallest part of the grain is the germ which is located at the base of the kernel. The germ is the part of the seed that if planted would sprout to form a new plant. It contains a good amount of polyunsaturated fat; therefore it is often removed during milling so that the grain product will be less likely to turn rancid. The germ is relatively rich in the B vitamins, vitamin E, and some minerals, and it contributes rich flavor to the grain product.