'essential' sugar

One of at least eight sugar compounds that act as building blocks to make a great variety of complex molecules, such as glycoproteins and glycolipids, that play an essential role in maintaining health and fitness. These molecules includeglucose, galactose, mannose, fucose, xylose, N-acetylglucosamine, N-acetylgalactosamine, and N-acetylneuraminic acid or sialic acid. The only truly essential sugar is glucose. The others are not strictly essential nutrients because our bodies can synthesize all of them from glucose. See also glyconutrient.