Mattar ,Rejane , Daniel Ferraz de Campos Mazo, Flair Jose’ Carrilho.2012. “Lactose intolerance: diagnosis, genetics and clinical factors”. Accessed April 11, 2013.


Lactose is a disaccharide that makes up the majority of mammalian milk and is also a major source of nutrition for new-borns until they are weaned. It is broken down by the enzyme lactase, which most people are born with, into glucose and galactose. Lactase activity is high at young ages such as birth to around two years old, but begins to decrease rapidly with age in some people(hypolactasia) grouped as “lactase non-persistence”. Those who maintain high lactase activity into adulthood are grouped as “lactase persistence”.

The LCT gene controls lactase persistence and non-persistence. The LCT13910CT and LCT13910TT genes are both found to be associated with lactase persistence, showing that the allele is still dominant in a heterozygous form, allowing the breakdown of lactose. However when the dominant LCT13910T is not present this results in lactose non-persistence, “lactose intolerance”. This may differ in different countries.

Lactose persistence and non-persistence can be tested by checking the body’s glucose and galactose level when lactose is ingested. Galactose metabolism is inhibited with ethanol to determine the glucose rise. A breathe test based on the fermentation of undigested lactose can be used as well as genetic testing.

The by-products of undigested lactose in the intestines, carbon dioxide, hydrogen, methane and short-chain fatty acids result in abdominal pains, flatulence and bloating. It also acidifies the colon which results in diarrhea. These symptoms may also be accompanied with others not related to the gut.

This paper was very in-depth about the topic. It is very easy to be lactose intolerant and not know it can be so complex. One may drink a glass or milk or some yogurt for breakfast and not fully understand why they have and urge to defecate (poop) or fluctuate. I would’ve never guessed that my body’s ability to ingest milk and tolerate it could be associated with my genetics. I would suggest this paper to anyone in need of answers to their milk-stomach related issues.

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