The term lactose intolerance, also known as lactase deficiency, refers to the development of gastrointestinal symptoms following the ingestion of milk or dairy products. Lactose intolerance is an extremely common disorder, with estimates indicating that between 30 and 50 million Americans suffer from lactose intolerance. It is much more prevalent in adults than in children and is more common among people of African descent, Hispanics, Asians and Native Americans. Lactose intolerance has a number of causes and is classified as one of three types:
- Primary lactose intolerance - Result of normal aging
Normally, your body produces large amounts of lactase at birth and during early childhood, when milk is the primary source of nutrition. Usually your lactase production declines as your diet becomes more varied and less reliant on milk. This gradual decline may lead to symptoms of lactose intolerance.
- Secondary lactose intolerance - Result of illness or injury
This form of lactose intolerance occurs when your small intestine decreases lactase production after an illness, surgery or injury to your small intestine. It can occur as a result of intestinal diseases, such as celiac disease, gastroenteritis and an inflammatory bowel disease like Crohn's disease. Treatment of the underlying disorder may restore lactase levels and improve signs and symptoms, though it can take time.
- Congenital lactose intolerance - Condition at birth
Rarely, babies can be born with lactose intolerance caused by a complete absence of lactase activity. This disorder is passed from generation to generation in a pattern of inheritance called autosomal recessive. This means that both the mother and the father must pass on the defective form of the gene for a child to be affected. Infants with congenital lactose intolerance are intolerant of the lactose in their mothers' breast milk and have diarrhea from birth. These babies require lactose-free infant formulas.
What are the symptoms of Lactose Intolerance . . .
Typically symptoms of lactose intolerance occur within thirty minutes to two hours following the ingestion of milk or milk-containing products. Common symptoms include:
- Abdominal cramping/discomfort
- Loose stools
- Acid Reflux
The severity of symptoms varies dramatically from person to person, ranging from mild to severe. Symptom severity will depend on how much lactase your body produces and how much lactose you consume.
What Causes Lactose Intolerance. . .
Lactose intolerance occurs when your body does not produce adequate levels of the digestive enzyme lactase. Lactase is a digestive enzyme needed in order to digest lactose, a sugar found most often in dairy products.
Normally, the lactase enzyme is produced by the cells that line your small intestine. When lactose reaches the small intestine, the lactase attaches to it in order to break it down into two simple sugars, glucose and galactose. These sugars can only be absorbed by the bowel once they have been separated. Once absorbed they are converted into energy for your body to utilize. However, without enough lactase, most of the lactose in your food will move unprocessed from the small intestine into the colon, where intestinal bacteria begin to interact with it (fermentation), causing the uncomfortable symptoms associated with lactose intolerance. The longer lactose stays in the colon, the more it will ferment, and the more problems it will cause.
Studies have shown that the activity of the lactase enzyme (necessary for digesting lactose) begins to decline between the ages of 3 and 5. Thus, most adults have relatively low levels of the lactase enzyme, making them prone to the development of symptoms of lactose intolerance. Lactose intolerance may be a significant problem in children. Some children with lactose intolerance have an inherited absence of the lactase enzyme called congenital lactose deficiency.
Populations Most Affected . . .
The prevalence of lactose intolerance among persons living in the United States varies between 20 and 60% by most estimates. Individuals from certain areas of the world are more likely to develop lactose intolerance and Americans whose families originate from those areas are affected at a higher rate. For example, almost all persons from Southeast Asia have lactose intolerance, while in Scandinavia and Northwestern Europe, the prevalence is between 3 and 8%. Lactose intolerance is very common in individuals from Southern Mediterranean regions such as Italy, and also is widespread among the indigenous population of Africa as well as among African-Americans. Most adults with lactose intolerance are thought to have this as part of the normal developmental process.