Malassimilation: Causes, Symptoms and Treatment

What Is Malassimilation?

Malassimilation is an umbrella term for all conditions in which nutrients from food cannot be adequately utilized by the body. It encompasses two related but distinct processes: maldigestion (impaired breakdown of nutrients in the gastrointestinal tract) and malabsorption (impaired uptake of nutrients through the intestinal mucosa into the bloodstream). Both processes may occur independently or together and ultimately result in the body being deprived of essential nutrients required for normal function.

Causes

The causes of malassimilation are diverse and can broadly be divided into those affecting digestion and those affecting absorption:

Causes of Maldigestion

• Exocrine pancreatic insufficiency: Insufficient production of digestive enzymes (e.g., lipase, amylase, proteases) by the pancreas impairs the breakdown of fats, carbohydrates, and proteins.
• Bile acid deficiency: Reduced bile acid production or impaired enterohepatic circulation (e.g., due to liver disease or resection of the terminal ileum) disrupts fat digestion.
• Achlorhydria: Absent or reduced gastric acid impairs enzyme activation and the initial digestion of food.

Causes of Malabsorption

• Coeliac disease: A gluten-triggered autoimmune reaction damages the small intestinal villi, significantly reducing the absorptive surface area.
• Crohn's disease: Chronic inflammation of the intestinal wall impairs nutrient uptake.
• Short bowel syndrome: Surgical removal of large segments of the small intestine reduces the available absorption area.
• Lactase deficiency: The absence of the enzyme lactase prevents the breakdown of lactose (milk sugar).
• Infections and parasites: Pathogens such as Giardia lamblia can damage the intestinal mucosa.
• Lymphatic disorders: Conditions such as intestinal lymphangiectasia impair the transport of absorbed nutrients.

Symptoms

Symptoms of malassimilation arise from chronic nutrient deficiency and the accumulation of undigested substances in the intestine:

• Steatorrhoea: Pale, bulky, greasy, and foul-smelling stools are a classic sign of impaired fat digestion or absorption.
• Chronic diarrhoea: Frequent, loose, or watery bowel movements.
• Weight loss: Despite adequate food intake, affected individuals lose weight.
• Bloating and abdominal pain: Undigested nutrients are fermented by intestinal bacteria, producing excess gas.
• Nutritional deficiencies: Depending on which nutrients are affected, symptoms may include anaemia (iron, folate, or vitamin B12 deficiency), osteoporosis (calcium deficiency), bleeding tendency (vitamin K deficiency), night blindness (vitamin A deficiency), and others.
• Fatigue and reduced performance: A consequence of general energy and nutrient depletion.
• Oedema: Severe protein deficiency can lead to fluid retention in the tissues.

Diagnosis

Diagnosing malassimilation requires careful investigation, as many different underlying conditions may be responsible:

• Medical history and physical examination: Assessment of symptoms, dietary habits, and pre-existing conditions.
• Stool analysis: Measurement of fecal fat content (fecal fat quantification) or detection of undigested food particles; exclusion of infections and parasites.
• Blood tests: Measurement of nutrient levels (iron, vitamin B12, folate, calcium, fat-soluble vitamins), inflammatory markers, and specific antibodies (e.g., anti-transglutaminase antibodies in suspected coeliac disease).
• Breath tests: For example, hydrogen breath tests to diagnose lactase deficiency or small intestinal bacterial overgrowth.
• Imaging: Ultrasound, CT, or MRI to assess the pancreas, liver, and intestinal tract.
• Endoscopy and biopsy: Small bowel biopsies to diagnose coeliac disease, Crohn's disease, or other mucosal abnormalities.
• Pancreatic function tests: For example, measurement of fecal elastase-1 to evaluate exocrine pancreatic function.

Treatment

Treatment is always directed at the underlying cause:

Treatment of the Underlying Condition

• For pancreatic insufficiency: Oral pancreatic enzyme replacement therapy (pancreatin) with meals.
• For coeliac disease: Strict, lifelong gluten-free diet.
• For Crohn's disease: Anti-inflammatory drugs, immunosuppressants, or biologics.
• For lactase deficiency: Low-lactose diet or lactase enzyme supplements.
• For bacterial overgrowth: Antibiotic therapy.

Nutritional Therapy and Supplementation

• Correction of nutritional deficiencies through targeted supplementation (e.g., vitamins, minerals, trace elements).
• Dietary adjustments tailored to individual tolerance (e.g., low-fat diet in steatorrhoea, frequent small meals).
• In severe cases, enteral nutrition (via a feeding tube) or parenteral nutrition (intravenous) may be required.

References

1. Feldman, M., Friedman, L. S., Brandt, L. J. - Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 11th edition. Elsevier, 2021.
2. World Gastroenterology Organisation (WGO) - Global Guidelines: Celiac Disease (2016). Available at: https://www.worldgastroenterology.org
3. Lomer, M. C. E. - Review article: the aetiology, diagnosis, mechanisms and clinical evidence for food intolerance. Alimentary Pharmacology and Therapeutics, 41(3), 262-275 (2015). PubMed PMID: 25471897.