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Lactose Intolerance

Description of Lactose Intolerance

Lactose intolerance is a widespread metabolic disorder caused by the inability to digest lactose due to a shortage of the lactase enzyme. Lactase activity is high during infancy, when milk is the main source of nutrition, and declines after the weaning phase in most mammals.

Approximately 75% of the world’s population loses the ability to digest lactose. The prevalence of adult type lactose intolerance varies depending on ethnicity, from less than 5% in north-western Europe to almost 100% in some Asian populations. Clinical symptoms of lactose intolerance usually begin 30 minutes to 2 hours after eating or drinking foods that contain lactose, such as dairy products.

The onset of symptoms is directly related to the quantity of ingested lactose. The severity of symptoms varies, depending on the amount of lactose each individual can tolerate.

It is important to distinguish lactose intolerance from other conditions, for example irritable bowel syndrome, which have very similar symptoms.

Common symptoms of lactose intolerance and conditions with similar symptoms

Typical symptoms after consuming food or drink containing lactose

Abdominal bloating

Abdominal pain



Failure to thrive

Nausea Steatorrhea (excess fat in stool)

Stomach cramps



Conditions with similar symptoms

Celiac disease

Cows’ milk protein allergy (casein and whey)

Crohn’s disease

Irritable bowel syndrome

Ulcerative colitis



Treatment for lactose intolerance includes a lactose-restricted diet.

The extent of dietary changes depends on how much lactose a person can consume without exhibiting symptoms.

Additionally, a lactose-intolerant individual may use commercially available lactase (LactAid, Lactase, DairyEase etc.), which reduces the lactose to glucose and galactose.


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