Galactose: what it is and what problems it can cause in children


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We already know that when a baby is born, many tests have to be carried out to check that it does not suffer from any allergies or any other problem or disorder. Each test follows a specific procedure and is done when the baby’s age is appropriate. One such test is the galactosemia test.

This disorder is related to the inability to break down galactose, one of many types of sugar. Galactosemia can be very problematic and even dangerous in infants, as breast milk contains sugar (among other things) and therefore galactose. We will now explain what this disorder is and how it is related to sugar in the body.

What is galactosemia?

This congenital disease is a genetic disorder, as it is caused by an error in the DNA sequence (on chromosome 9), which is inherited if both parents have the genetic error even if they do not develop symptoms. It is classified as a rare disease, occurring in 1 in 50,000 people. Galactosemia affects the way the body metabolises or converts food into energy. These can be divided into 3 main groups: carbohydrates (sugars), proteins and fats. Each has a way of being processed in the body so that they can be converted into energy or fuel for the body.

For this to happen, several processes have to take place within us. Each group will have a way of metabolising thanks to a body protein or enzyme. If an error appears in one of them, the food accumulates because it is not ‘processed’ and can be dangerous to health. This is what happens in the case of galactosemia: sufferers are unable to metabolise, in this case, galactose.

We said that this disorder was especially dangerous for babies because breast milk is basically made up of a large part of sugar. It is made up of 2 types of sugars: glucose and galactose. Some galactosemia patients can tolerate the first type, but not the second. This is not only true for breast milk, but also for any product containing lactose (cheese, dairy products, cow’s milk or milk from other animals…).

For galactose to be metabolised, the enzyme galactose-1-phosphate-uridyl transferase must be present. If there is none, too little or in a defective form, it is impossible for the body to metabolise and all metabolites accumulate. These are not destroyed but, in order not to accumulate, are directed to other pathways, where galactitol accumulates.

It is especially dangerous if this metabolite is stored in large amounts in the liver, brain, kidneys or other organs, as this is when the first symptoms of galactosemia occur. This would be the classical one, but there are other less common types (due to alteration of other enzymes). The key, as always, is to detect this disorder early, if possible during the first weeks of life, so that it can be controlled and greater problems can be avoided.



This disease is complex to diagnose. It usually manifests itself during the first weeks of life, on contact with breast milk or formula. The most common symptoms are:

  • Seizures.
  • Irritability.
  • Lethargy.
  • Poor nutrition.
  • Refusal of food with milk.
  • Little weight gain.
  • Jaundice (yellowing of the skin, mucous membranes and eyes).
  • Vomiting.
  • Hepatomegaly.
  • Liver failure.
  • Blood disorders (haemolysis).
  • Hypoglycaemia.
  • Elevated ammonia levels.


Galactosaemia, as mentioned above, is difficult to diagnose because all these symptoms do not necessarily occur at the same time or instantaneously. If the disorder is mild and untreated, it can cause cataracts at ages when they should not develop, delayed infant development, intellectual disability, speech disorders, ataxia, growth retardation and missed menstrual periods. If galactosemia is severe, it can cause much greater, even fatal, problems for the baby.

Even if treated, some children with galactosemia may have intellectual disabilities, language problems, motor problems, immune deficits, ovarian failure and even decreased bone density. It is very important to note the symptoms in the first few days and after breastfeeding or formula feeding, and to consult the doctor or paediatrician if you have any doubts or any signs that you notice in your baby.



The diagnosis of galactosaemia is made when the above symptoms are observed, especially if accompanied by lightheadedness, diarrhoea or vomiting and jaundice. For this purpose, the paediatrician performs a routine examination of the baby, especially if he sees that there is a possibility that he is suffering from it, such as getting sick when he drinks milk and getting better when his diet consists only of intravenous fluids.

As galactosemia is inherited, the baby will be tested for it quickly if it is known that the parents or someone in the family has galactosemia. This can already be checked during gestation by taking a sample of the amniotic fluid amniotic fluid (amniocentesis) or by chorionic villus sampling (with a sample of the placenta).

A baby is also considered positive for galactosemia if, in a urine test for reducing sugars, a tablet introduced into the patient’s urine causes the liquid to change to a particular colour. However, the official diagnosis of classical galactosemia is made by the determination of galactose-1-phosphate-uridyl transferase in blood, a test that is performed only in a few specialised laboratories, such as at Ambar Lab.



Galactosemia as such cannot be cured, but it can be treated by eliminating from the diet any food or product containing galactose or lactose. This disease should never be confused with lactose intolerance, as the consumption of a food or liquid containing lactose in a galactosemia patient can be serious and cause serious problems. For this purpose, babies or patients with this disorder are often given special milks without galactose in their components, usually based on soya.

It is very important, in addition to early detection, to follow the instructions of health professionals, as by the time the condition is diagnosed, the baby is often already very ill and may require hospital and even intensive care. If they manage to overcome liver failure and sepsis, they improve rapidly if any lactose intake is stopped and they receive the necessary care.


Allowed and forbidden foods for people with galactosemia

The foods that people with galactosaemia can consume are quite varied for a disease that affects intake. These include:

  • Pasta.
  • Cereals.
  • Eggs.
  • Animal fats.
  • Most vegetables.
  • Meat (except offal).
  • Fish (except viscera).


It should be noted that galactose is not only found in milk and milk products. It is also found in fruits, peas, dates, figs, chickpeas, lentils and beans. If a strict diet is followed, the patient can minimally tolerate galactose in the diet if very carefully controlled and in specific amounts in some foods:

  • Soybeans.
  • Cocoa.
  • Pumpkin.
  • Brussels sprouts.
  • Kiwi.
  • Yeast.
  • Peppers.
  • Sunflower seeds.
  • Leek.
  • Tomato.
  • Watermelon…


Certain patients can tolerate pulses, but these decisions cannot be taken lightly and of their own free will, but have to go through a doctor. It should also be borne in mind that people with galactosaemia need to make up for the lack of calcium with permitted calcium-containing foods or dietary supplements, as they are unable to consume dairy products.

It is very important to consider whether the medicines consumed by a patient with this disorder contain lactose (if it exceeds 5 grams, it has to be declared) or galactose.


Prognosis of galactosemia

The prognosis of galactosemia is usually quite favourable if treatment is undertaken as soon as the disease is detected and before the baby’s condition becomes critical. Any manifestation of the disorder is usually reversible (including cataracts). If a galactose-free diet is not followed, the prognosis depends on the percentage of the enzyme present in the body. As explained above, untreated galactosemia is lethal, although there are milder forms that progress without many symptoms into adulthood.

As we have learned, galactosemia is an inherited disorder that causes the affected person to have a deficiency in one or several sets of enzymes that result in galactose not being able to be broken down. This leads to a build-up of this enzyme, which eventually damages several organs, especially the liver, brain, kidneys and eyes. It is the deficiency of one of these 3 enzymes (or several) that causes this disease:

  • Galactose-1-phosphatidyl transferase (GALT) deficiency. It is the most common and, at the same time, the most serious.
  • Galactose kinase (GALK) deficiency.
  • Galactose-6-phosphate epimerase (GALE) deficiency.


Early prevention will always help to mitigate the effects of the disease or to start personalised treatment. Hence, in Ambar Lab we specialise in laboratory testing. Today we have more than 3,000 laboratory tests and we carry out clinical reference analyses, managing them so that they can be integrated in an agile and flexible way into your laboratory’s operations.

If you need more information or have any questions about our process, please contact us at us. Whether you are a hospital, a laboratory, a drug developer or a medical researcher, we have the answer to all your needs.



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