What is lactose intolerance?
In the intestine, during digestion, the lactose (a natural sugar of dairy products) is usually split into glucose and galactose by a specific digestive enzyme, the lactase. This enzyme is located in the membrane of the absorptive cells of the small intestine, the enterocyte. As lactose is the main nutrient during infancy (brought in Human milk for example), the lactase activity may decline progressively after childhood. In case of reduced lactase activity, some lactose remain not digested. This is the lactose maldigestion. Non-digested lactose enters the colon where it is digested by the gut microbiota. For most individuals, this lactose maldigestion produces few or no symptoms and has no direct consequence on health. It concerns most people in the World; it’s a normal process, usually not noticeable. When this lactose maldigestion brings digestive symptoms such as bloating, diarrhea, and flatulence, it is called lactose intolerance.
Lactose intolerance can on the contrary impair quality of life but has, likewise, no direct consequence on health. However, because self-diagnosed or even diagnosed lactose intolerance can lead to an unfounded limitation or avoidance of dairy products, lactose intolerance could result in nutrient shortcomings, such as low calcium intake, which may result in adverse health effects.
How to diagnose lactose intolerance?
It is not possible to self-diagnose lactose intolerance. The proper way to diagnose lactose intolerance, called the Breath test, is to measure, in the exhaled air, the hydrogen produced by the gut microbiota after consumption of a standard dose of lactose (usually 20 to 50 g). This diagnosis is performed under medical control and it is only complete when one or many of the following symptoms occur: bloating, diarrhea, and flatulence.
This medical diagnosis is especially important as, when it is performed; only 50 % of self-diagnoses of lactose intolerance are confirmed.
Is lactose intolerance an allergy?
Lactose intolerance is not to be confused with cow’s milk protein allergy. In cow’s milk allergy, the immune system overreacts to one or more proteins contained in cow’s milk (such as casein and whey proteins. Symptoms include hives, swelling, nausea and wheezing can arise within an hour and even up to 72 hours after drinking cow’s milk.
Could dairy product be consumed by lactose intolerant?
Several medical organizations (NMA, NIH, EFSA, FAO…)* recommend that lactose intolerants should not avoid dairy foods in order to prevent nutrients shortcomings. Instead, these medical organizations advise lactose intolerants to adapt their diet, and particularly recommend the consumption of yogurt. WGO has put forth a similar statement, to consume fermented dairy products containing probiotics, with proven benefits on digestive health. It is even a tip from their 10 global diet and lifestyle tips on how to improve digestive health.
In order to consume the recommended daily intake of calcium among others, lactose intolerants can consume other forms of dairy products such as cheeses that contain low or no lactose, and more specifically yogurts that contain live bacteria, which improve the digestion of the lactose contained in yogurt.
Lactose intolerants can also consume food containing lactose in modest amounts, up to 12 g in one intake or up to 24 g (the equivalent of one or two bowls of milk, respectively), preferably in fractioned amounts across the day, during meals, without triggering any symptoms.
The regular consumption of lactose-containing food by lactose maldigesters could even lead to colonic adaptation by the gut microbiota and may allow them to tolerate more lactose.
Lactose-free food or total avoidance of dairy food is only needed for rare infants with congenital lactase deficiency (a very rare genetic disease).
Nevertheless, the elimination of a particular type of food could lead to nutritional imbalances and may have significant health consequences.
*NMA (National Medical Association), NIH (the National Institutes of Health, a part of the U.S. Department of Health and Human Services), EFSA (the European Food Safety Agency), WGO (the World Gastroenterology Organization) and FAO (the Food and Agriculture Organization of the United Nations).
Could yogurt be consumed by lactose intolerant?
Yogurt is a fermented food, type of predigested food that contains sugars, proteins and fats, broken into simple forms. Yogurt is recommended for people with lactose intolerance
Lactose maldigesters and lactose intolerants can consume yogurt because the lactose in yogurt is digested more efficiently than any other dairy sources and it is even recommended to contribute to calcium daily intake
Yogurt is a form of fermented milk that contains live bacteria, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, at least 108 live microorganisms per gram of yogurt. These bacteria produce their own lactase, which breaks down some of the lactose contained in yogurt. Live cultures in yogurt improve digestion of lactose in yogurt in individuals with lactose maldigestion. This claim is, moreover, approved by the European Food Safety Authority. Therefore, for lactose maldigesters and intolerants, yogurt is an easy way to have dairy and digest lactose.