Lactose intolerance refers to the malabsorption of lactose due to a deficiency in lactase enzymes. Lactase deficiency is present in around 70% of the population but not all exhibit symptoms of lactose intolerance.
Where is lactose found?
It is predominantly found in dairy products such as:
- Milk
- Butter
- Cheese
- Cream
- Yoghurt
- Ice cream
It may also be found in many processed foods such as cereals, baked foods (such as bread, crackers, cakes, biscuits), sauces and dressings, protein shakes.
🔢 Classification
There are 4 different types of hypolactasia which differ in their acquisition:
- Primary hypolactasia - this is due to non-persistence of lactase. The enzyme levels deplete with age. It begins after weaning but symptoms only start after 2 years or later. This is considered normal while a persistence of lactase is seen in certain mutations, especially in individuals whose ancestors consumed large amounts of dairy.
- Secondary hypolactasia - this is also known as acquired hypolactasia. It occurs in people with gastrointestinal illnesses that damage the brush border of the small intestines. This incudes diseases like coeliac disease, viral gastroenteritis, giardiasis, etc.
- Congenital hypolactasia/alactasia - this is a rare autosomal recessive disorder which is life-threatening. Very few cases have been reported globally.
- Developmental hypolactasia - this is seen in premature infants who have not yet developed a fully mature intestinal brush border that can host a sufficient amount of lactase enzyme.
Pathophysiology
Lactose is a disaccharide. This means it is made up of two monosaccharides - glucose and galactose. In order for us to absorb lactose in our gut, we need lactase to break down lactose → glucose + galactose. In addition to the lactase enzyme, some of the microflora in the gut also are able to convert lactose into its building block components. All mammals have the highest amount of lactase concentrations shortly after birth before rapidly declining after the age of weaning.
Hypolactasia is the abnormal metabolism of lactose which leads to the symptoms felt in lactose intolerance. However, not all cases of hypolactasia result in symptoms. It is dependent on the amount of lactose reaching the colon as well as the microflora in the colon
Undigested lactose moves into the colon, where it interacts with bacteria present in the colon. These bacteria ferment lactose, producing gases such as hydrogen, methane, and carbon dioxide which are what cause the symptoms present.
⚠️ Risk factors
- Non-white ethnicity
- Adolescence
- Family history
- Enteritis or gastroenteritis - causes secondary hypolactasia.
- Irritable bowel syndrome diagnosis - as misdiagnosis between IBS and lactose intolerance can occur due to the similarity in presentation.
😷 Presentation
Symptoms develop minutes - hours after ingestion of lactose:
- Diarrhoea
- Abdominal pain
- Abdominal distension and bloating - this is due to the fermentation of gases that occur.
- Flatus - due to methane production.
- Vomiting
- Lethargy
🔍 Investigations
🥇🏆 Lactose elimination trial - there should be resolution of symptoms once lactose is eliminated from the diet.
Other tests may include:
- FBC - if anaemia is present it is more likely another disease.
- Hydrogen breath test - a raised level of hydrogen in the breath may indicate lactose intolerance.
🧰 Management
- 🏆 A lactose-free diet is the gold standard. However, if not tolerated then oral lactase supplements can be used.
- 💡 Vitamin D and calcium supplementation can be considered to reduce the risk of osteopenia.
- If it is secondary to an underlying disease, then treatment of underlying cause is the most important aspect of management.
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