Baked food product. It is made of flour or meal that is moistened into a dough, kneaded, and usually leavened with yeast. A major food since prehistoric times, bread has been made worldwide in various forms using a variety of ingredients and methods. Flat, unleavened bread, the earliest form, is still eaten in the Middle East, Asia, and Africa. The principal grains used in such breads are wheat, barley, millet, buckwheat, rye, and corn. Raised bread, common in Europe and the U.S., is usually made of wheat or rye. Both contain the elastic protein substance gluten, which traps gas produced by fermentation during leavening, helping the bread to rise. While the simplest breads contain only flour, water, and yeast, other common ingredients are milk, shortening (fats, butter, oils), salt, eggs, and sugar. Bread is a source of complex carbohydrates and B vitamins (see vitamin B complex); whole-wheat bread contains more protein, vitamins, minerals, and fibre than white-flour bread. See also baking.