Glucose is the only monosaccharide present in maltose. Each unit of maltose is composed of two units of glucose. Its isomer, isomaltose, is also composed solely of glucose.
Maltose is a disaccharide, or sugar, made up of two monosaccharides. It is the rarest naturally occurring disaccharide, and it occurs primarily in sprouted grains high in starch. It is a product of starch breakdown and glucose caramelization. Maltose is also known as malt sugar.
Maltose is found naturally in malt, potatoes and cereal grains, and it is added to processed foods and beverages as a sweetener. Maltose also occurs in beer and pasta due to the ingredients used to make them. Humans are able to digest maltose in their food with the help of the enzyme maltase. Individuals who are deficient in maltase may suffer from maltose intolerance.
Maltose intolerance causes gas, bloating, diarrhea or vomiting when maltose is ingested. Since starch breaks down into maltose as part of the digestion process, avoiding maltose alone is not sufficient enough to prevent symptoms. Intolerance to another disaccharide, sucrose, is caused by the same genetic defect that leads to maltose intolerance. In a similar manner to maltose, sucrose is produced when more complex carbohydrates are digested, which makes it equally difficult to avoid.