The most common grains were rye, barley, buckwheat, millet and oats. Rice remained a fairly expensive import for most of the Middle Ages and was grown in northern Italy only towards the end of the period. Wheat was common all over Europe and was considered to be the most nutritious of all grains, but was more prestigious and thus more expensive. The finely sifted white flour that modern Europeans are most familiar with was reserved for the bread of the upper classes. As one descended the social ladder, bread became coarser, darker, and its bran content increased. In times of grain shortages or outright famine, grains could be supplemented with cheaper and less desirable substitutes like chestnuts, dried legumes, acorns, ferns, and a wide variety of more or less nutritious vegetable matter.