Genetics Northern California


Galactosemia is a condition that occurs when the body lacks an enzyme needed to break down (metabolize) milk sugar into galactose. When this enzyme is missing, galactose builds up in the body and causes damage to the brain, liver, eyes, and kidneys. Newborns with untreated galactosemia can develop severe infections and/or die within the first few weeks of life.

The most common source of galactose is lactose (milk sugar). Lactose is found in all dairy products. Another source of galactose can be found in the fiber of some fruits and vegetables. When these foods are eaten, the body makes galactose. The body uses three different enzymes to break down (metabolize) the lactose. These three enzymes are called galactokinase, Galactose-1-phosphouridyl transferase [GALT], and UDP-GAL-4-epimerase. Galactokinase goes to work first and breaks galactose down into Galactose-1-Phosphate (Gal-1-P). Then the other two enzymes break Gal-1-P down into even smaller parts: GALT produces Glucose-1-P and UDP-GAL-4-empimerase produces UDP-glucose. When one of these enzymes is missing or not working properly, either galactose or Gal-1-P builds up in the body, and both can cause serious problems.

Galactose or Gal-1-P can build up in the body in one of two ways. Sometimes the person eats too many foods that have galactose in them. However, there is another way levels can rise and it is less easy to control. All people, even those with galactosemia, can make galactose inside their bodies without knowing about it. For instance, the body might sense that there is not enough galactose and will try to make some on its own. In people without galactosemia this works just fine, but it can cause big problems for those whose bodies cannot handle galactose. This is why some people who are on strict galactose-free diets, might still have higher levels of galactose or Gal-1-P in their blood.

Whether the source of the galactose is from the diet (exogenous) or the result of the body making it on its own (endogenous), high levels can lead to cataracts, developmental delays, speech disorders, and/or liver disease. Unfortunately, some of these complications can occur even with good control. In addition, almost 90% of all women with galactosemia have ovarian failure and are unable to become pregnant.

Galactosemia is an inherited disorder. The mode of inheritance is called autosomal recessive, meaning that each parent carries a gene for the disorder that is passed on to the baby. Genes give the body the instructions it needs for growth and healthy development. They come in pairs and a baby receives one copy of each gene from the mother and one from the father. Everyone has some genes that have the potential to cause serious disease. Whether they do or not is beyond human control. There is nothing any parent can do to cause or prevent a change in a gene.

"Autosomal" means that the condition can affect both males and females. "Recessive" means that the person with the disorder has two copies of the non-working gene: one from the mother and one from the father. Although each parent carries one of these non-working genes, they do not have the disorder themselves. This is because they each also carry a working gene, and the one working copy of the gene is able to keep their metabolism working normally. People with one working and one non-working gene are considered to be "carriers" for the condition.

When both parents are carriers for a metabolic condition, there is a 1 out of 4 chance (25%) that they will both pass on the recessive gene and have an affected child. If only one parent passes along the recessive gene, the child will be unaffected, but will be a carrier for the condition like the parents. The chance of this happening is 2 out of every 4 pregnancies (50%). And finally, the child may inherit neither of the recessive genes and will neither have the condition nor be a carrier. The chance of this happening is also 1 out of every 4 pregnancies (25%). It is important to understand that two parents who are carriers of galactosemia face the same risks for each pregnancy, regardless of how many affected or unaffected children they have previously had. For example, carrier parents who have had two affected children have the same chance in their third pregnancy of having an affected child as carrier parents who have two unaffected children. The risk is always 1 in 4 (25%).

Within the first few days of life, all babies born in California have a simple blood test that checks for the presence of galactosemia. Through early detection and prompt treatment, some of the serious effects of galactosemia can be prevented.

The goal of treatment for galactosemia is to keep the blood levels of galactose and Gal-1-P consistently low in order to try to avoid the poor consequences of having high levels. We stress the word "try" because there is still so much about the way galactosemia works that is unknown. We do know that very high levels almost always lead to poor outcomes. However, having low levels is not necessarily a guarantee against these poor outcomes. There are unfortunate cases in which the person maintained low levels, but still experienced complications. Therefore, the treatment for galactosemia is based on minimizing the known risk of high levels by trying to keep the levels as low as possible.

This effort consists of three main parts: diet, formula, and monitoring.

  1. Diet
    Please keep in mind that when we refer to "eating" that this includes any eating, drinking, swallowing, and chewing. When we refer to "foods", this includes all foods, drinks, medications, and even gum.

    The main aim of treatment is to limit the amount of galactose (also called GAL) that the person eats. This means that people with galactosemia must learn what types of food have galactose and roughly how much. To make this easier, foods can be divided into three categories: HIGH (Red Light), MEDIUM (Yellow Light) and LOW (Green Light). For instance all dairy products are Red Light foods. Examples of Yellow Light foods include many common fruits and vegetables that have galactose, such as peas, tomatoes, apples, and bananas. Green Light foods are those fruits and vegetables that either have no galactose or only small amounts. People with galactosemia must be particularly diligent about reading the ingredients on packaging because dairy products such as the milk proteins, whey and casein, are often used in many processed foods.

    Depending on the severity of the disorder, each individual is given guidelines for the amount of galactose they can eat. Although some people must avoid it altogether, it is okay for many people with galactosemia to eat some galactose. This is because, unlike a food allergy, eating galactose will not cause an allergic-type of reaction. Instead the focus is on not allowing the overall blood levels to get too high by keeping track of how much is eaten throughout the day.

  2. Formula
    The second part of the treatment for galactosemia is to make sure the person eats a nutritionally balanced diet. This can be difficult given the many food restrictions, especially for the nutrients found in dairy products such as calcium and Vitamin D.

    One thing that can help is including one of the following formulas in the diet:

    A soy-based infant formula (e.g., Isomil)  OR fortified rice milk.

    à Please Note: Rice milk is not a substitute for infant soy-based formulas for young children.

    Almost all people with galactosemia are started on a soy-based formula as infants, and then simply continue to drink it throughout their lives in order to make up for the vitamins and minerals lacking in the typical galactose-restricted diet. Fortified rice milk, plus a multivitamin supplement, is an alternative to those who do not wish to remain on Isomil. These two formulas are important to maintaining the health of those with galactosemia as it is virtually impossible to meet the daily vitamin and mineral requirements and stick to the recommended diet.

  3. Monitoring
    The final part of the treatment for galactosemia is monitoring. Monitoring helps make sure the other two parts of the treatment (diet and formula) are working to keep the galactose levels low. It is important to find out if the treatment is working in order to minimze the chance for medical problems. 

    Blood test: For those with GALT deficiency (the most common form of galactosemia) the blood is tested regularly for Gal-1-P. The level of Gal-1-P will be high if the body has more galactose than it can cope with. As mentioned above, this can either be the result of the individual’s diet or the endogenous creation of galactose. Testing for Gal-1-P requires a routine blood draw in the hospital lab. The sample is then sent outside of Kaiser to a lab that specializes in this particular test.

    Urine test: There is another test that uses a urine sample (instead of blood) to monitor for a by-product of galactose called galactitol. This test is called Urine Galactitol and is often used in conjunction with the Gal-1-P blood test to help determine how much galactose there is inside the body. Testing for Urine Galactitol requires a 10ml sample of urine to be frozen and shipped to a lab outside of Kaiser that specializes in this particular test.

    Other, less frequent, tests that are used to monitor people with galactosemia include liver function blood tests (ALT, AST), ultrasounds/CTs to visualize the liver, and hormone testing to check the function of the ovaries.


For more information about galactosemia visit:

Parents of Galactosemic Children, Inc - A national, non-profit, volunteer organization whose mission is to provide information, support, and networking opportunities to families affected by galactosemia

Galactosemia Association of the North Eastern States (GANES) - A nonprofit organization whose mission is to create and strengthen networking among individuals and families affected by galactosemia.

Understanding Galactosemia: A Diet Guide (available through the Regional Metabolic Clinic)
by Lauri Hartz, MS, RD, Kim Pettis, RD, Sandy Van Calcar, MS, RD

Parent's Guide to Galactosemia - Part 1 - Parent handout from the California Newborn Screening Program for babies up to six months of age.

Parent's Guide to Galactosemia - Part 2 - Parent handout from the California Newborn Screening Program for children six months and older.

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Published by Parenting Press, Inc., Seattle, WA, 1998

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Published in 1992 by Random House. Suggested ages: 4-8
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