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Disorder-Specific Survival Kit: Galactosemia
Galactosemia is an inherited disorder characterized by an inability of the body to utilize galactose. Galactosemia means "galactose in the blood ". Galactose is a type of food sugar found mainly in dairy products, and is produced within the body as well. The main source of galactose in the diet is milk products. Milk contains a sugar called lactose, and during digestion, lactose is broken down into the sugars glucose and galactose. Glucose can be used as a source of energy by the body, but galactose needs to be further broken down by a specific chemical (enzyme) before it can be utilized.
Persons with galactosemia have very little or entirely lack an enzyme that helps the body break down galactose. There are three different enzyme problems that can lead to galactosemia. This information will focus on the most common type of galactosemia, often called "classic galactosemia". The enzyme that is reduced or missing in classic galactosemia is called galactose-1-phosphate uridyl transferase (GALT). The GALT enzyme enables the body to break down galactose into glucose for energy. Because some individuals with galactosemia have more enzyme than others, the severity and treatment of the disorder can vary.
Galactosemia is treated by removing foods that contain galactose from the diet. Any foods containing lactose, thereby containing galactose, should be avoided. Untreated galactosemia will result in a harmful build-up of galactose and galactose-1-phosphate (a form of galactose) in the bloodstream and body tissues. Infants with unrecognized galactosemia usually have problems with feeding and do not grow as they should. If galactosemia is not treated, infants can develop cataracts, liver disease and kidney problems. In addition, the build-up of galactose and galactose-1-phosphate can cause brain damage, and in some cases, can lead to death. Even with treatment, some children may develop learning disabilities, and girls with galactosemia may have problems with their ovaries. With continued dietary management, however, many individuals with galactosemia enjoy good health, and are able to lead independent lives.
The goal of dietary treatment for galactosemia is to minimize galactose intake and thus minimize galactose-1-phosphate production. Galactose-1-phosphate levels are determined by
It is not possible for a person with galactosemia to have a galactose-free diet. However, all persons with galactosemia should limit galactose intake from foods to a very low level. The galactose-1-phosphate levels of the individual determine the degree of dietary restriction necessary.
Because milk and milk products are the most common food source of galactose, persons with galactosemia should avoid these foods. In the past, there was some controversy about how long a person with galactosemia should remain on a galactose-restricted diet. It is now recommended that persons with galactosemia should avoid eating foods with galactose throughout life.
A galactose-restricted diet should keep blood galactose-1-phosphate (gal-1-p) below 3 to 4 mg/100 ml, while containing enough nutrients for normal body function. The diet allows most protein-containing foods other than milk and milk products. Fruits, vegetables, grains, breads, fats and sugars are acceptable, as long as they do not have ingredients that contain galactose. Some fruits and vegetables do contain small amounts of galactose. However, the form of galactose (bound galactose) found in fruits and vegetables is not usable by the body, and may not contribute to elevated blood gal-1-p. Recent research has shown that bound galactose may in fact be usable by the body, but further studies are needed to confirm this.
Milk and milk products are the usual dietary source of calcium. Because persons with galactosemia remove milk products from their diet, they need to add calcium back into their diet through supplements. All people with galactosemia should have a regular daily supplement of calcium either from a soy formula or tablets. Consult your doctor or nutritionist to find out how much calcium supplementation is right for you.
Foods high in galactose. Some foods contain obvious galactose and are unacceptable:
The galactose content of some foods is provided as a reference.
Foods with moderate amounts of galactose. Some foods contain moderate amounts of galactose and are limited as needed to support appropriate galactose-1-phosphate levels.
Foods with more than 10 mg Galactose/100 gram of food:
Foods with 5-10 mg Galactose/100 gram of food:
Acceptable foods and ingredients:
Genes are the basic units of hereditary material. Every cell of our body contains approximately 80,000 genes. Genes contain the instruction code or "blueprint" that directs the development and function of each cell and tissue in the human body. Genes, in turn, are packaged on larger structures called chromosomes. Each chromosome contains several thousand genes.
Genes and chromosomes exist in pairs. Every cell has 23 pairs of chromosomes containing two copies of every gene. Each person received one copy of every gene from their mother in the egg cell, and one from their father in the sperm cell. Most often, genes function properly. In some cases however, a change, or mutation in a gene can cause it to not function. Mutations in certain genes can cause inherited, or genetic disorders.
The gene mutation that causes galactosemia is inherited in what is called an autosomal recessive pattern. This means that a non-working copy of the gene must be inherited from both parents for a child to be affected with the disorder. The parents health is not affected because the other copy of the gene is working correctly, and compensates for the non-working copy. Parents of children who have an autosomal recessive disorder are called "carriers" of the disorder. This is because they themselves do not have the disorder, but can have sons and daughters who are affected. It is important to remember that every person carries several non-working recessive genes. Only when both parents carry the same non-working gene is there a chance of having a child with a recessive disorder.
Unfortunately, there is no way for parents to know if they carry the non-working gene that causes galactosemia until they have a child with the disorder.
The chance that two parents who carry the same non-working gene will have a child with a recessive disorder is one in four, or 25% with each pregnancy (see diagram 2). The chance these parents will have a child who is a carrier of the disorder like themselves is one in two, or 50% with each pregnancy. There is also a one in four, or 25% chance that these parents will have a child who is neither affected nor a carrier of the disorder. Both sons and daughters of carrier parents have the same chances of inheriting the genes that cause galactosemia.
The gene that codes for galactose-1-phosphate uridyl transferase (GALT) is located on chromosome 9. Many different mutations within this gene have been identified, and the most common mutation is called "Q188R". Most people with galactosemia have this mutation. A milder form of galactosemia known as the "Duarte variant" is also caused by a mutation within the GALT gene. Different changes within the GALT gene are what lead to variations in enzyme levels between individuals with galactosemia.
Parents of Galactosemic Children
This groups mission is to maximize the potential for normal development of the individual with galactosemia. Some of the resources they provide are parent support, newsletter, galactosemia literature and dietary information.
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last updated: 11/01/2007