Carbohydrate intolerance

Carbohydrates, which include sugars and starches, are the body's primary source of energy and, along with fats and proteins, one of the three major nutrients in the human diet. Carbohydrate intolerance is the inability of the bodyto completely process the nutrient carbohydrate into a source of energy for the body, usually because of the deficiency of an enzyme needed for digestion.

Digestion of food begins in the mouth, moves on to the stomach, and then intothe small intestine. Along the way, specific enzymes are needed to process different types of sugars. When these enzymes are inadequate, the result is carbohydrate intolerance.

Carbohydrate intolerance can be primary or secondary. Primary deficiency is caused by an enzyme defect present at birth or developed over time. The most common is lactose intolerance. Secondary deficiencies are caused by a diseaseor disorder of the intestinal tract, and disappear when the disease is treated. These include protein deficiency, celiac disease, tropical sprue, and someintestinal infections. In cancer patients, treatment with radiation therapyor chemotherapy may affect the cells in the intestine that normally secrete lactase, leading to intolerance.

Lactose intolerance, the inability to digest the sugar found in milk, is widespread and affects up to 70% of the world's adult population and is the mostcommon of all enzyme deficiencies. Deficiencies in enzymes other than lactaseare extremely rare.

The severity of carbohydrate intolerance symptoms depends on the extent of the enzyme deficiency, and range from a feeling of mild bloating to severe diarrhea. In the case of a lactase deficiency, undigested milk sugar remains in the intestine, which is then fermented by the bacteria normally present in theintestine. These bacteria produce gas, cramping, bloating, a "gurgly" feeling in the abdomen, and flatulence. In a growing child, the main symptoms are diarrhea and a failure to gain weight. In an individual with lactase deficiency, gastrointestinal distress begins about 30 minutes to two hours after eating or drinking foods containing lactose. Food intolerances can be confused with food allergies, since the symptoms of nausea, cramps, bloating, and diarrhea are similar.

Sugars that aren't broken down by enzymes cause the body to push fluid into the intestines, which results in watery diarrhea. Diarrhea may flush other nutrients out of the intestine before they can be absorbed, causing malnutrition.

Carbohydrate intolerance can be diagnosed using oral tolerance and blood tests. To identify lactose intolerance in children and adults, the hydrogen breath test is used to measure the amount of hydrogen in the breath. The patient drinks a beverage containing lactose and the breath is analyzed at regular intervals. If undigested lactose in the large intestine (colon) is fermented bybacteria, it produces hydrogen, which is carried by the bloodstream into thelungs where it is exhaled. Normally there is very little hydrogen detectablein the breath, so its presence indicates faulty digestion of lactose.

No treatment currently exists to improve on the body's ability to produce digestive enzymes, but symptoms can be controlled by diet. Carbohydrate intolerance caused by temporary intestinal diseases disappears when the underlying condition is successfully treated.

Because the degree of lactose intolerance varies so much, treatment should betailored for the individual. Young children showing signs of intolerance should avoid milk products; infants should switch to soy-based formula. Older children and adults can adjust their intake of lactose depending on how much and what they can tolerate. Generally, small amounts of lactose-containing foods taken throughout the day are better tolerated than a large amount consumedall at once.

For those individuals who are sensitive to even very small amounts of lactose, the lactase enzyme is available without a prescription. It comes in liquidform for use with milk. The addition of a few drops to a quart of milk can reduce the lactose content by up to 90%. Chewable lactase enzyme tablets are also available. Three to six tablets taken before a meal or snack will aid in the digestion of solid foods. Lactose-reduced milk and other products are alsoavailable in stores. The milk contains the same nutrients as regular milk.

Because dairy products are an important source of calcium, people who reduceor severely limit their intake of dairy products may need to consider other ways to consume an adequate amount of calcium in their diets.

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