Indeed, the ability to digest lactose (a type of sugar naturally found in milk and dairy products) is due to the persistence of lactase (an enzyme) in the intestine, where lactose is transformed into glucose and galactose, for energy and various functions. Lactase activity reaches its maximum at birth and slowly declines after weaning. Lactase activity may persist in some populations where dairy products are consumed into adulthood, especially Caucasians from Northern Europe (Scandinavia, the British Islands and Germany) and specific communities in Asia, Africa, South America, Southern Europe and Australia.
Lactose intolerance can occur in individuals with lactose maldigestion, the reduced capacity to digest lactose, which consumes large amounts of lactose in one intake (>12 g) or during the day (>24 g) apart from meals.
Lactose intolerance is a type of lactose maldigestion, which results in one or more of the following symptoms: bloating, diarrhea, and flatulence.
Similar symptoms of lactose intolerance can be observed after consumption of some short-chain carbohydrates, the FODMAP (Fermentable, Oligo-, Di-, Mono-saccharides And Polyols), which are poorly absorbed in the small intestine.
Lactose maldigesters, including lactose intolerants, can consume foods containing lactose, such as dairy products, in small amounts. Yogurt consumption is particularly encouraged since yogurt contains live ferments, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, which have been officially acknowledged to improve digestion of lactose in yogurt, in individuals with lactose maldigestion.
For more information about lactose-free food, please go to question 19.