Rye is a cereal grain that is similar to wheat but longer and much more thinner and varies in color from yellowish brown to grayish green. Rye is an excellent source of fiber, selenium, phosphorus, protein and magnesium. It is generally available in its whole or cracked grain form or as flour or flakes that look similar to old-fashioned oats. It is difficult to separate the germ and bran from the endosperm of rye. Rye flour usually retains a large quantity of nutrients, in contrast to refined wheat flour.