Lactase Deficiency (Age-Dependent)
Overview
Plain-Language Overview
Lactase deficiency is a common condition where the body produces less lactase, an enzyme needed to digest lactose, the sugar found in milk and dairy products. This often develops with age, leading to difficulty digesting dairy after childhood. People with this condition may experience symptoms like bloating, gas, diarrhea, and stomach pain after consuming dairy. It is not a disease but a natural decrease in enzyme production. Many individuals manage symptoms by adjusting their diet or using lactase supplements.
Clinical Definition
Lactase deficiency, also known as lactase non-persistence, is characterized by a decreased production of the lactase enzyme in the small intestinal brush border, leading to impaired hydrolysis of lactose into glucose and galactose. This condition typically manifests after weaning, with a progressive decline in lactase activity during late childhood or adolescence. The resulting undigested lactose reaches the colon, where bacterial fermentation produces gas and osmotic diarrhea. It is genetically determined in most populations, with varying prevalence worldwide. Symptoms include abdominal cramping, bloating, flatulence, and diarrhea following lactose ingestion. Diagnosis is supported by clinical history and confirmed by tests such as the lactose hydrogen breath test or lactose tolerance test. It is important to differentiate lactase deficiency from secondary causes of lactose malabsorption due to mucosal injury. Management focuses on dietary modification and symptom relief. The condition is benign and does not cause permanent intestinal damage.
Inciting Event
- Introduction or increased consumption of lactose-containing dairy products.
- Gastrointestinal infections or injury that transiently reduce lactase expression.
Latency Period
- none
Diagnostic Delay
- Symptoms often attributed to other causes such as irritable bowel syndrome or food intolerance.
- Lack of awareness about lactase deficiency as a common cause of gastrointestinal symptoms.
Clinical Presentation
Signs & Symptoms
- Postprandial abdominal pain and cramping.
- Bloating and increased flatulence due to fermentation of lactose.
- Watery diarrhea following lactose ingestion.
- Nausea and occasional borborygmi (rumbling bowel sounds).
History of Present Illness
- Postprandial bloating, abdominal pain, and diarrhea occurring within hours of consuming lactose-containing foods.
- Symptoms improve with lactose avoidance or use of lactase enzyme supplements.
- May report flatulence and nausea after dairy ingestion.
Past Medical History
- History of gastrointestinal infections or inflammatory bowel disease may worsen symptoms.
- No prior history of congenital lactase deficiency.
Family History
- Often a positive family history of lactase deficiency or lactose intolerance in first-degree relatives.
- Ethnic background with familial patterns of lactase persistence or deficiency.
Physical Exam Findings
- Abdominal distension may be observed due to gas accumulation.
- Bowel sounds are typically normal or slightly hyperactive.
- No signs of peritoneal irritation or abdominal tenderness.
Diagnostic Workup
Diagnostic Criteria
Diagnosis of lactase deficiency is primarily based on clinical symptoms of lactose intolerance following dairy ingestion, supported by objective testing. The lactose hydrogen breath test is the preferred diagnostic tool, showing increased breath hydrogen after lactose ingestion due to bacterial fermentation. Alternatively, the lactose tolerance test demonstrates a blunted rise in blood glucose after lactose intake. Genetic testing may identify lactase persistence or non-persistence alleles. Secondary causes must be excluded by clinical evaluation and, if needed, intestinal biopsy. A positive diagnosis requires symptom correlation with test results indicating impaired lactose digestion.
Pathophysiology
Key Mechanisms
- Age-dependent decline in lactase enzyme activity in the small intestinal brush border leads to impaired lactose digestion.
- Undigested lactose reaches the colon, where bacterial fermentation produces gas and short-chain fatty acids, causing symptoms.
- Osmotic effect of undigested lactose draws water into the intestinal lumen, resulting in diarrhea.
| Involvement | Details |
|---|---|
| Organs | Small intestine is the organ where lactose digestion occurs via lactase activity. |
| Tissues | Intestinal mucosa contains the brush border where lactase is expressed. |
| Cells | Enterocytes in the small intestine produce lactase enzyme on their brush border membrane. |
| Chemical Mediators | Lactase is the enzyme responsible for hydrolyzing lactose into glucose and galactose. |
Treatment
Pharmacological Treatments
Lactase enzyme supplements
- Mechanism: Provide exogenous lactase to digest lactose in the intestine
- Side effects: bloating, abdominal pain, diarrhea
Non-pharmacological Treatments
- Avoidance of lactose-containing foods such as milk and dairy products.
- Use of lactose-free or lactose-reduced dairy alternatives.
- Gradual introduction of small amounts of lactose to improve tolerance.
Prevention
Pharmacological Prevention
- Oral lactase enzyme supplements taken before dairy ingestion to improve lactose digestion.
Non-pharmacological Prevention
- Avoidance or limitation of lactose-containing foods such as milk and soft cheeses.
- Use of lactose-free dairy products or dairy alternatives like almond or soy milk.
- Gradual introduction of small amounts of lactose to increase colonic adaptation.
Outcome & Complications
Complications
- Dehydration from severe diarrhea in rare cases.
- Nutritional deficiencies such as calcium and vitamin D deficiency due to dairy avoidance.
| Short-term Sequelae | Long-term Sequelae |
|---|---|
|
|
Differential Diagnoses
Lactase Deficiency (Age-Dependent) versus Celiac Disease
| Lactase Deficiency (Age-Dependent) | Celiac Disease |
|---|---|
| Normal small bowel mucosa without villous atrophy | Villous atrophy on small bowel biopsy |
| Negative serologic markers for celiac disease | Positive anti-tissue transglutaminase (tTG) antibodies |
| Symptoms improve with lactose avoidance rather than gluten restriction | Symptoms improve with a gluten-free diet |
Lactase Deficiency (Age-Dependent) versus Irritable Bowel Syndrome (IBS)
| Lactase Deficiency (Age-Dependent) | Irritable Bowel Syndrome (IBS) |
|---|---|
| Symptoms triggered by lactose ingestion | Abdominal pain relieved by defecation |
| Positive lactose hydrogen breath test indicating malabsorption | No specific malabsorption or enzyme deficiency |
| No relief of symptoms with defecation | Normal lactose hydrogen breath test |
Lactase Deficiency (Age-Dependent) versus Small Intestinal Bacterial Overgrowth (SIBO)
| Lactase Deficiency (Age-Dependent) | Small Intestinal Bacterial Overgrowth (SIBO) |
|---|---|
| Positive lactose hydrogen breath test with late peak after lactose ingestion | Positive glucose hydrogen breath test with early peak |
| No underlying motility disorder or anatomical abnormality | Associated with risk factors like altered motility or anatomical abnormalities |
| Symptoms improve with lactose restriction rather than antibiotics | Response to antibiotic therapy |