Lactose Intolerance Causes

Symptoms

Approximately 30 minutes to 2 hours after ingestion of foods containing lactose, the following digestive symptoms occur. The symptoms occur only after a certain amount is ingested (e.g., 12-18 g of lactose), are dose-dependent, and vary greatly among individuals:

Other symptoms may include bowel sounds, stomach rumbling, nausea, vomiting, constipation and general symptoms.

Causes

In order for the disaccharide lactose (milk sugar) to be absorbed into the body from food, it must be broken down in the intestine by the enzyme lactase into its two components glucose and galactose. Lactase is mainly found in the jejunum, the middle section of the small intestine, and is anchored in the apical cell membrane of the enterocytes. The cause of lactose intolerance is a reduced lactase concentration in the small intestine due to a lactase deficiency. The lactose cannot be digested or can only be partially digested and reaches the large intestine. There, water is increasingly retained osmotically. In addition, the lactose is fermented by the bacterial flora to fermentation products such as carboxylic acids (acetic acid, butyric acid, propionic acid) and gases (hydrogen, methane, carbon dioxide). Causes of lactase deficiency: Primary adult lactase deficiency: Lactase deficiency is usually physiological, i.e. it is not a disease but a normal development. The highest concentrations are measured at birth. After weaning, lactase concentrations drop rapidly in all mammals and continue to drop throughout life. In Europeans, it can take up to 20 years for the concentration to reach its lowest level. Secondarily, lactase deficiency can be triggered by a number of diseases. Underlying this is damage to the mucosa of the small intestine, for example due to viral gastroenteritis, chemotherapy or trauma. Acquired lactase deficiency may disappear over time. Inherited (congenital) primary congenital lactase deficiency with complete lack of enzyme activity is extremely rare. In this form, diarrhea occurs at the first breastfeeding. Premature babies: Lactase is formed in the last weeks of pregnancy, therefore premature babies often cannot break down lactose and do not tolerate breast milk. The unborn baby is intolerant until the 34th week of pregnancy.

Trigger

The triggers are foods containing lactose, such as dairy products, for example milk, cream, cheese, condensed milk, powdered milk, whey, buttermilk, feta, cottage cheese, and ricotta. The amount of lactose varies greatly depending on the product. Lactose is “hidden” in many products. It is added to many foods as an additive, for example bread, breakfast cereals, salad dressings or sweets. Lactose is a common excipient in medicines such as tablets, powders, granules and in alternative medicines (e.g. Schüssler salts).

Risk factors

  • Ethnicity: while many people of European origin (Northern Europeans, white Americans, Australians) can digest lactose well even in adulthood, the prevalence of lactose intolerance in Indians, Latin Americans, blacks, and Asians is significantly increased, ranging from 20% to 100%. Primary lactose intolerance affects about 70% of the world’s population (!).
  • Southern Europeans: the prevalence is significantly higher in southern Europe (25%) than in northern Europe (2%).
  • Heredity
  • Age: Lactase concentration decreases with increasing age.

Complications

It is important to know that lactose intolerance, unlike other food intolerances (such as celiac disease!), does not cause mucosal damage. Dairy products can therefore continue to be consumed, even if acute symptoms occur. If dairy products are avoided, calcium deficiency and loss of bone density may result. The risk of osteoporosis is increased in people with lactose intolerance.

Diagnosis

For trial self-diagnosis, 3 dl of milk can be drunk and observed below to see if symptoms occur.

  • Medical history
  • H2-Breath test: Measurement of hydrogen in breath after ingestion of lactose (elevated).
  • Lactose intolerance test: Measurement of blood glucose levels after ingestion of lactose (reduced).
  • Biopsy of the small intestine
  • Genotyping (in exceptional cases)

Differential diagnoses

Non-drug measures

The most important measure is to reduce the consumption of foods rich in lactose. However, complete abstinence is usually not necessary or desirable because milk contains important minerals (calcium) and vitamins, among other things. Most patients can consume small, tolerable amounts throughout the day. Tolerance must be tested on an individual basis. Lactose-free milk is commercially available. Rice milk and soy milk are lactose-free, but the taste takes some getting used to. Mammalian milk such as goat’s milk contains lactose. Acidified dairy products such as yogurt, soured milk, cottage cheese, and aged cheeses are relatively well tolerated because some or all of the lactose has been broken down by lactic acid bacteria. Hard cheeses such as Gruyère and Emmental can be consumed without problems because they no longer contain lactose. Aids: food diary, tables of compatible foods, apps.

Drug treatment

Lactase (e.g., Lacdigest, dietary supplement) is a beta-galactosidase that breaks down milk sugar into glucose and galactose. The drug is taken immediately before eating a meal containing lactose and can increase tolerance, for example when eating out at a restaurant. Calcium and vitamin D substitution for insufficient intake of dairy products and calcium-containing foods. Probiotics: Bacteria with lactase activity can break down milk sugar (e.g., lactobacilli). In case of secondary lactose intolerance, the underlying disease should be treated. Low-lactose adapted milk is commercially available for lactose-intolerant infants, for example Aptamil Pregomin. Aptamil Pregomin is also used for food allergies and intestinal disorders.