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Genes Behind Lactose Intolerance

Genes behind lactose intolerance

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Lactose intolerant individuals are unable to digest the milk sugar lactose, causing gastrointestinal symptoms such as bloating, cramps, flatulence, and diarrhoea. Genes are the main determinant and cause of this inefficiency.

Key takeaways

  1. Genetic tests are a useful determinant in whether a person has primary lactose intolerance
  2. Some individuals have no problem digesting lactose
  3. Fermented dairy foods cause fewer issues for lactose intolerant people

Genetic tests are a useful determinant in whether a person has primary lactose intolerance as there are two main genes involved in this process: the LCT gene and the MCM6 gene.

During adulthood, lactose intolerance is caused by the gradual decrease in the LCT gene activity after infancy, with this process occurring in most humans. The LCT gene provides instructions for the creation of lactase enzyme in the small intestine. This enzyme helps us to digest lactose, a sugar found in milk and other dairy products, and is controlled by a DNA sequence within the MCM6 gene called the regulatory element.

Some more fortunate individuals have inherited changes in this element, which help them to digest lactose throughout their lives thanks to sustained lactase production. This is a mutation caused by the MCM6 gene which controls whether the LCT gene is turned on or off. People without these changes, with their LCT gene turned off, usually suffer from lactose intolerance symptoms as they are not able to digest lactose.

Being a lactose-intolerant individual can be managed in daily life without any extensive inconveniences. Most people with lactase non-persistence can include varying amounts of lactose in their diets without experiencing symptoms. Fresh milk is marked as the main cause of the symptoms while eating other dairy products such as yoghurt or cheese could be possible without any major discomfort. This is mostly because these foods are made using fermentation processes which breaks down much of the lactose in milk.



Work Cited:

Swagerty Jr, D. L.,Walling, A. D., & Klein, R. M. (2002). Lactose intolerance. American familyphysician65(9), 1845-1850.

Heyman MB (2006).”Lactose Intolerance in Infants, Children, and Adolescents”. Pediatrics (Review). 118 (3): 1279–1286.

Savaiano DA,Levitt MD (1987). “Milk intolerance and microbe-containing dairy foods”. J. Dairy Sci. 70 (2):397–406.

Deng Y, Misselwitz B, DaiN, Fox M (2015). “Lactose Intolerance in Adults: Biological Mechanismand Dietary Management”. Nutrients (Review). 7 (9): 8020–35.

Lactose intolerance – Genetics Home Reference. (n.d.). Retrieved August 21,2017, from

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