Lactose Intolerance

Lactose intolerance is the condition in which lactase, an enzyme needed for proper metabolization of lactose, is not produced in adulthood. A lactose tolerance test, a hydrogen breath test, or a stool acidity test is required for a clinical diagnosis. Lactose intolerance can sometimes be confused with milk allergy, the former is a lack of the enzyme lactase, the latter is an autoimmune reaction to milk proteins.

With lactose intolerance, the result of consuming too much lactose is excess gas production, stomach aches and often diarrhea. Most lactose-intolerant adults can drink about 250 ml (8 oz) of milk per day without severe symptoms.

The majority of humans stop producing significant amounts of lactase sometime between the ages of two and five. A relatively recent genetic change caused some populations, including many northern Europeans, to continue producing lactase into adulthood. Lactose intolerance is an autosomal recessive trait, while lactase-persistence is the dominant allele. The gene is expressed and the enzyme synthesized if at least one of the two genes are able to express properly. Only when both gene expressions are affected is lactase enzyme synthesis reduced, which in turn reduces lactose digestion.

There is no "cure" to lactose intolerance. There have been some cases where the intolerance has somehow diminished with time; this has not been studied scientifically, however, and whether it is a case of desensitization remains to be seen. It should be remembered that lactose intolerance is not a binary condition: the reduction in lactase production, and hence, amount of lactose that can be tolerated varies from person to person, and may change with age. The management of lactose intolerance involves avoiding lactose-containing products, use of alternative products, such as soya-derived milk substitute, or lactase enzyme medication.

...More at Wikipedia  

Related Links:

• US National Library of Medicine
• Mayo Clinic

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