| Food & Diet

Are You Galactose Intolerant?

By Tyler Woodward


What Is Galactose?:

What Is Galactose

Galactose is one of the three simple sugars or carbohydrates that are found in nature, glucose and fructose being the other two. Galactose and glucose are nearly identical in chemical structure, both sharing the same chemical formula C6H12O6. The only difference between glucose and galactose is the location of one hydroxyl group within the 6-carbon ring. Although this slight difference makes a big difference in digestion. 

Galactose is not naturally found on its own in nature and is only found within lactose. Lactose is the type of sugar that is notoriously found in milk and dairy products and is made up of one molecule of glucose and one molecule of galactose. 

Unlike glucose, galactose cannot be directly assimilated into the bloodstream and must be processed into another form. After the lactose molecule is broken down galactose can be processed in two ways:

  1. Galactose is converted into glucose-1-phosphate - Through a 2-step process galactose can be converted into glucose-1-phosphate which is able to be assimilated into the cell and either used to create energy through glycolysis or to be stored as energy through glycogenesis.
  2. Galactose is converted into galactitol - Galactitol is a sugar-alcohol that is said to be toxic in high concentrations.  Unless you are unable to produce the galactokinase enzyme, which converts galactose into galactose-1-phosphate, or are diabetic you do not have to worry about the accumulation of excess galactitol

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Galactose Metabolism:

Galactose Vs Sugar


There are a number of genetic conditions that can interfere with properly metabolizing galactose. 

  1. Galactokinase Deficiency - This prevents your body from producing the galactokinase enzyme and thereby prevents your body from converting galactose into galactose-1-phosphate. Without this enzyme galactose cannot converted into its end product of glucose and must be converted into galactitol.
  2. Galactokinase-1-phosphate Uridyltransferase Deficiency - This prevents your body from producing the Galactokinase-1-phosphate uridyltransferase enzyme which prevents you from converting galactose-1-phosphate into the end-product of glucose-1-phosphate. This is the most dangerous of all disorders that prevents you from digesting galactose and you must avoid lactose if you lack this gene.
  3. Lactose Intolerance - This occurs from an inability to produce the lactase enzyme which breaks apart glucose and galactose. The lactase enzyme is thought to degrade in many people over time with age. If lactose cannot be digested via the lactase enzyme it makes it into the colon and ferments in the gut which can cause indigestion, bloating, gassiness and general discomfort. If you are lactose intolerant it’s not deadly to consume lactose, but it can cause severe discomfort. 

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How Does Galactose Differ From Sucrose:

Galactose differs from sucrose being that it is a type of monosaccharides, meaning it only contains one sugar molecule while sugar is a disaccharide and contains one molecule of glucose and one molecule of fructose. Galactose is also not found by itself in nature and is always found as part of the sugar, lactose. 

Is Galactose Healthy?:

Is Galactose healthy?

Unless you lack the enzymes necessary to process or digest galactose or lactose there is no evidence to indicate that galactose is any more or less healthy than other forms of sugars. If you do possess any of the genes that prevent you from digesting lactose properly then it’s likely a good idea to avoid any foods that contain lactose. 


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