Monosaccharides are the simplest carbohydrates and are classified according to whether they are aldehyde or ketone derivatives, as well as the number of atoms contained in the molecule. Single hexoses, glucose and galactose require no digestion and can be absorbed directly into the bloodstream. Hexoses contain six carbon atoms, and are found in foods, while pentoses, ribose and deoxyribose contain five carbon atoms and are produced during the metabolism of foodstuffs.

Three common sugars—glucose, galactose, and fructose, share the same molecular formula: C6H12O6. Because of their six carbon atoms, each is a hexose. Although all three share the same molecular formula, the arrangement of atoms differs in each case. Substances such as these three, which have identical molecular formulas but different structural formulas, are known as structural isomers.

• Glucose
  "Blood sugar" is the immediate source of energy for cellular respiration. Glucose, which is also referred to as dextrose, is a moderately sweet sugar found in vegetables and fruit. When glucose is fermented by the enzyme zymase, in yeast, it results in the formation of carbon dioxide and ethyl alcohol. It is the basic structure to which all carbohydrates are reduced to in the end, for transport via the bloodstream and use by the cells of the body.

  Two different pathways are involved in the metabolism of glucose: one anaerobic and one aerobic. The anaerobic process occurs in the cytoplasm and is only moderately efficient. The aerobic cycle takes place in the mitochondria and results in the greatest release of energy. As the name implies, though, it requires oxygen.

• Galactose
  Galactose is not normally found in nature, but is mostly hydrolyzed from the disaccharide lactose, which is found in milk, as part of a disaccharide made by glycosidic linkage to a glucose molecule. The lactose disaccharide from milk is a major energy source for almost all animals, including human. Although not very water-soluble, and less sweet than glucose, it forms part of glycolipids and glycoproteins, which is found in many tissues. The body can change glucose to galactose in order to enable the mammary glands to produce lactose.

  Galactose is natural and is a basic component of many things, being found in milk, tomatoes and many fruits and vegetables. There is only one product range in the world that uses galactose as a basic food and drink ingredient, and that is a brand new range of energy drinks.

  Galactose has uniquely different properties compared to other sugars. These properties make it easier to lose and maintain weight; they are useful in warding off adult-onset diabetes; they give much steadier energy through time, and they provide the basis for products for athletes which allow them to perform better and longer. Galactose is a remarkable undiscovered sugar for the new Millennium.

• Fructose
  Fructose's chemical name is levulose. Fructose is also called the fruit sugar. Fructose is found in fruits, honey, and the sole sugar in bull and human semen. It is the sweetest of sugars. It is used for preventing sandiness in ice cream. The compound's formula is C6H12O6. It is shaped in orthorhombic, bispherodial prisms.

  Fructose taken in large quantities is associated with gastrointestinal distress, and is also associated with increases in the fat content of blood following meals rich in this. A large quantity of fat in the blood is thought to be a major risk factor for heart disease.