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Page: Lactose Intolerance
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Lactose intolerance (or hypolactasia) is the condition in which lactase, an enzyme needed for proper metabolization of lactose (a sugar that is a constituent of milk and other dairy products), 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. In reality, the former is a lack of the enzyme lactase, while the latter is an aberrant immune response (usually) 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 (McGee 2004; Swagerty et al, 2002).
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.
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Important notice:
The content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other
qualified health provider with any questions you may have regarding a medical condition.
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