Galactose: Nutrition Information, Function, Sources, Absorption and Metabolism

It is a simple sugar, which belongs to simple carbohydrates.

Galactose is composed of the same elements as glucose, but has a different arrangement of atoms. Its name comes from the Greek word milk, and -osa, which denotes sugar.

Galactose nutrition information:

  • Calories per gram = 4.1
  • Sweetness relative to sucrose = 30%
  • Net carbohydrates = 100%

Is galactose an essential nutrient?

Galactose is not an essential nutrient, which means you do not need to get it from food to be healthy; Galactose can be synthesized in the human body from glucose.

Functions in the human body

In the human body, most of the ingested galactose is converted into glucose, which can provide 4.1 kilocalories per gram of energy, which is approximately the same as sucrose.

Galactose can bind to glucose to produce lactose (in breast milk), lipids to form glycolipids (for example, molecules that make up blood groups A, B and AB) or proteins to form glycoproteins (for example, in cell membranes).

Sources of galactose

  • The main source of the galactose diet is the lactose in milk and yogurt, which is digested to galactose and glucose.
  • Foods that contain small amounts of free galactose include low-lactose milk or lactose-free milk, certain yogurts, cheeses, creams, ice cream and other foods artificially sweetened with galactose.
  • Simple natural foods (fruits, vegetables, nuts, grains, fresh meats, eggs, milk) generally contain less than 0.3 g of galactose per serving.
  • Certain medications may contain galactose as a filler.

Other nutrients that contain galactose

  • Lactose is a disaccharide that contains galactose and glucose.
  • The galactans are oligosaccharides containing different monosaccharides, of which at least one is galactose.


Galactose is absorbed in the small intestine by the same mechanism as glucose, that is, with the help of transport proteins SGLT-1 and GLUT-2 in the lining of the small intestine.

In the rare genetic disorder; glucose-galactose malabsorption, the absorption of galactose and glucose is reduced.

Metabolism and galactose

Most of the galactose absorbed enters the liver, where it is converted primarily into glucose, which is then incorporated into glycogen or used as energy.

The effect of dietary galactose on blood glucose levels

Galactose ingestion results in lower levels of blood glucose and insulin than ingestion of glucose.

In one study, 75 grams of glucose ingested 30 minutes before exercise was metabolized primarily during the first hour of exercise and the same amount of galactose (on another occasion), during the third hour of exercise.

This means that the consumption of both glucose and galactose in the food before exercise could provide a better distribution of energy than any nutrient alone.

Galactose and lactose can promote tooth decay.


Galactosemia or “galactose diabetes” is a rare genetic disease in which the lack of one of the enzymes needed to convert galactose into glucose results in the accumulation of galactose in the blood and subsequent damage to the liver, brain, kidneys and eyes

When babies with galactosemia are fed breast milk or formula containing galactose or lactose, they may develop lethargy, enlarged liver, hypoglycemia, seizures, or jaundice in the first few days of their lives.

Galactosemia can not be treated, but symptoms can be prevented with a strict diet for life without galactose and without lactose.

Other genetic disorders of galactose metabolism include type 1 glycogen storage disease with enlarged liver and altered growth and galactokinase deficiency, a benign disorder with cataract present at birth.

Galactose and cooking

  • It is commercially available as an odorless white crystalline powder, approximately 30% as sweet as sucrose.
  • It is not hygroscopic, it does not attract moisture easily.
  • The solubility of galactose in water at 25 ° C is 215 g / 100 ml. Galactose is slightly soluble in ethanol.
  • The melting point of galactose is 325-336 ° F (163-169 ° C).
  • It is a reducing sugar, which is easily subjected to the browning reaction of Maillard in the presence of amino acids.
  • The caramelization of the galactose begins at 320 ° F (160 ° C).