Lactose Intolerance and Health: Program and Abstracts. NIH Consensus Development Conference, February 22-24, 2010

摘要

Lactose intolerance is the inability to digest significant amounts of lactose, a sugar found in milk and other dairy products. Lactose intolerance is caused by a shortage of the enzyme lactase, which is produced by expression of the lactase-phlorizin hydrolase gene by the cells that line the small intestine. Lactase breaks milk sugar down into two simpler forms of sugar called glucose and galactose, which are then absorbed into the bloodstream. Infants of every racial and ethnic group worldwide produce lactase and successfully digest lactose provided by human milk or by infant formulas. However, by the time many of the worlds children reach the age of 3- 4 years, expression of intestinal lactase ceases. Most affected individuals referred to as lactase nonpersisters in the United States belong to minority groups, especially Asians, African Americans, Hispanics, Native Americans, Alaskan Natives, and Pacific Islanders. Consumption of lactose-containing products by lactase nonpersisters may cause gas production, bloating, abdominal pain, and diarrhea. These symptoms of lactose intolerance are caused by intestinal bacterias fermentation of undigested lactose and often cause individuals to avoid lactose-containing products. Lactose intolerance can be diagnosed by drinking one to two large glasses of milk after fasting and measuring breath hydrogen levels a few hours later. Other diagnostic tools include analyzing an intestinal biopsy sample or determining the genetic makeup of the chromosomal region coding for lactase. However, many individuals mistakenly ascribe symptoms of a variety of intestinal disorders to lactose intolerance without undergoing testing. This becomes intergenerational when self-diagnosed lactose-intolerant parents place their children on lactose-restricted diets in the belief that the condition is hereditary. Healthcare providers are concerned that many lactose-intolerant individuals are avoiding dairy products, which constitute a readily accessible source of calcium and are fortified with vitamin D and other nutrients. Therefore, these individuals may not be meeting recommended intakes of these essential nutrients. Insufficient intakes of calcium carry a risk of decreased bone mineral density. This may have effects on bone health and increase the risk of fracture throughout the lifecycle, especially in postmenopausal women. Very low intake of vitamin D can lead to the development of rickets, especially in those of African descent and other highly pigmented individuals. Although milk alternative products are typically fortified with vitamin D and other nutrients, they are often more expensive and less widely available than conventional products.