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Updated: Nov 4, 2022

During the first 6 months of life, the main carbohydrates consumed come from breast milk or commercial milk which contains lactose. As we age, the body naturally becomes less tolerant of dairy products. Many still eat these foods in adulthood and some tolerate them better than others. This text explains what lactose is, lactose intolerance and also why some people are lactose tolerant.

What is lactose?

Lactose is a disaccharide. It is a sugar made up of 2 saccharide molecules, glucose and galactose.

(Wikipedia, 2021)

Lactose is present in dairy products, such as cow's and goat's milk, ice cream, yogurts etc. It should be noted that some dairy products have a higher concentration of lactose. For example, cow's milk has a higher lactose concentration than cheeses.

Lactose intolerance

To digest lactose, those who tolerate it produce enough enzymes called lactase. This molecule is produced in the small intestine and digests lactose. In other words, it breaks down lactose into 2 sugar molecules, glucose and galactose, which are digestible in our small intestine (Ruiz, 2020).

(Michigan State University, n.a.)

Lactose intolerance is a partial or complete inability to digest lactose. An intolerant person does not have this enzyme or does not have enough of this enzyme. So all or part of the lactose travels to the colon. Then, it can ferment with the bacteria that are naturally found there. This can cause discomfort, such as bloating, gas, and even diarrhea. To counter this problem, one can abstain from eating dairy products, take smaller amounts of these foods, take lactose-free products or fortified plant substitutes, take enzymes before the consumption of dairy products, get informed about foods that contain lactose, etc.

Each person is different. It is possible to find your tolerance threshold with trial and error. In fact, 2 meta-analyzes were carried out on the threshold of tolerance to lactose. The authors conclude that the majority of the intolerant population can tolerate up to 12 g of lactose without or with mild symptoms (Wilt et al., 2010 and Savaiano et al., 2006).

Who tolerates lactose?

About 70% of the world's adult population has some degree of lactose intolerance. Those who still tolerate it in adulthood have a genetic mutation that is beneficial since it allows them to digest dairy products without problems. (Corgneau et al. 2017).

In general, populations whose dairy products have been an important food source since a long time are more lactose tolerant. Therefore, the prevalence of lactose intolerance is low for people of northern European origin and middle for those of African, Latin, Eastern European and South African origin. Furthermore, the prevalence is highest for several Asian populations (Paige, 2005).

I hope you enjoyed reading,

Karine Drouin RD



Corgneau, M., Scher, J., Ritie-Pertusa, L., DTL, L., Petit, J., Nikolova, Y., Banon, S., Gaiani, C. (2017). Recent advances on lactose intolerance: Tolerance thresholds and currently available answers. Crit Rev Food Sci Nutr. 57(15), 3344–3356. https://10.1080/10408398.2015.1123671

Foster, P.L. (2019). Can changing the microbiome reverse lactose intolerance? Retrouvé le 28 décembre 2020 au

Michigan State University. (n.d.). Lactase. Retrouvé le 29 Janvier 2021 au

Paige, D. M. (2005). Lactose Intolerance in Infants, Children, and Adolescents. Pediatrics. 118(3)1279-1286.


Ruiz, A. R. (2020). Intolérance au lactose. Manuel Merck. Retrouvé le 26 décembre 2020 auérance-au-lactose

Savaiano, D. A., Boushey, C. J. and McCabe, G. P. (2006). Lactose intolerance symptoms assessed by meta-analysis: A grain of truth that leads to exaggeration. J. Nutr.136:1107–1113. Https://10.1093/jn/136.4.1107

Wikipédia. (Janvier, 2021). Lactose Intolerance. Retrouvé le 29 Janvier 2021 au

Wilt, T. J., Shaukat, A., Shamliyan, T., Taylor, B. C., MacDonald, R., Tacklind, J. et al. (2010). Lactose Intolerance and Health. Agency for Healthcare Research and Quality (US), Rockville, MD. Retrouvé le 23 Janvier 2021 au

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