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Maldigestion and Malabsorption

Maldigestion and Malabsorption Definition

Maldigestion means incomplete breakdown of nutrients in the gastrointestinal tract, usually due to lack of digestive enzymes.

Malabsorption means impaired transport of nutrients from the intestine into the blood.


Causes of maldigestion or malabsorption include [1]:

  • Severe liver disease with reduced bile production can result in maldigestion of fats and malabsorption of fat-soluble vitamins A, D, E and K.
  • Chronic pancreatic disease with reduced production of the enzymes lipase, amylase and trypsin can result in maldigestion of fats, carbohydrates and proteins.
  • Small intestinal disorders, such as celiac disease, Crohn’s disease, lactose intolerance, fructose malabsorption, small intestinal bacterial overgrowth (SIBO) and intestinal parasites can affect absorption of various nutrients.
  • Reduced amount of acid in the stomach (achlorhydria or hypochlorhydria) can affect the digestion of proteins and absorption of folate, vitamins B12 and C and minerals calcium, non-heme iron, magnesium and zinc.
  • Autoimmune gastritis can result in impaired absorption of vitamin B12.
  • Other causes of malabsorption:
    • Chronic diarrhea of any cause
    • Disorders of the nerves, blood or lymphatic vessels that supply the gut
    • A surgical removal of the stomach or gastric bypass – a surgical modification of the stomach intended to assist weight loss
    • Surgical removal of a large part of the small intestine resulting in short bowel syndrome (SBS), mainly in infants
    • Medications (check drug-nutrient interactions for each nutrient separately), chemotherapy, radiation therapy of the intestine

Symptoms and Signs

Symptoms and signs of maldigestion or malabsorption depend on the involved nutrients [2].

1. Watery Diarrhea

Watery diarrhea is usually caused  by maldigestion or malabsorption of carbohydrates.

  • Starch maldigestion may be due to the lack of an enzyme pancreatic amylase.
  • Fructose malabsorption is due to the deficiency of fructose-transporting protein in the small intestine.
  • Lactose intolerance is due to the lack of an enzyme lactase. Specific stool and breath tests for mentioned disorders are available.

2. Steatorrhea

Steatorrhea, which means white, loose, sticky, floating and foul smelling stools, speaks for fat malabsorption, which can result from a small intestinal, liver, pancreatic or bile duct disorder. Chronic fat malabsorption is usually accompanied with malabsorption of fat-soluble vitamins (A, D, E, K).

Unintentional Weight Loss

Weight loss can result from chronic diarrhea of any cause, especially due to malabsorption of carbohydrates or fats, for example in celiac or Crohn’s disease, chronic pancreatitis or severe liver disease.


Fatigue can result from malabsorption of fats, carbohydrates, minerals (iron) or vitamins (mainly vitamins from B complex, vitamin C and D).

Abdominal Bloating and Gas

Common causes of bloating and gas related to malabsorption:

Body Swelling (Edema)

Protein malabsorption, which can occur in celiac disease, Crohn’s disease, liver or pancreatic disease, can result in general body swelling, which is most visible in the legs, abdomen (ascites) and face. Swelling is due to low concentration of the blood protein albumin, which results in the escape of water from the blood vessels into the surrounding tissues.

Skin, Hair and Tongue Changes

  • Paleness in anemia due to iron, folate or vitamin B12 deficiency
  • Seborrheic dermatitis — areas of greasy and scaly skin in vitamin A deficiency
  • Rough, scaly skin (pellagra) in vitamin B3 (niacin) deficiency
  • Sore tongue in vitamin B2, B3 and B12 deficiency
  • Rashes, such as dermatitis herpetiformis (in celiac disease) or erythema nodosum
  • Hair loss (alopecia)

Vision Loss

Vitamin A deficiency can result in loss of night vision.

Painful and Brittle Bones

Malabsorption of vitamin D can result in soft and brittle bones – in children, the condition is known as rickets and in adults as osteomalacia [2].

Tingling and Numbness in the Feet and Muscle Weakness

  • Impaired absorption of vitamins B, for example, in celiac disease or alcoholism, can result in nerve damage (peripheral neuropathy) with tingling, numbness and muscle weakness [3].
  • Impaired absorption of calcium and magnesium can result in muscle cramps.


Impaired absorption of vitamins B1 (thiamin) and B3 (niacin) can result in dementia.


A doctor can suspect the presence of maldigestion or malabsorption from:

  • Blood tests that reveal low levels of various minerals, vitamins and proteins
  • Stool tests that reveal increased amount of reducing sugars or fats
  • Breath tests that can reveal fructose malabsorption and lactose intolerance

Additional investigations to find the cause of maldigestion or malabsorption include:

  • Endoscopy with biopsy — the investigation of the stomach and small intestine with a tube with light on the end during which samples of the tissue can be taken and checked under the microscope
  • Blood levels of liver enzymes to check for the function of the liver and pancreatic enzymes for the function of the pancreas


Treatment of maldigestion or malabsorption can include:

  • Supplements: minerals, vitamins, proteins, fatty acids or pancreatic enzymes
  • Treatment of the underlying disorder
  • Special diets, for example, gluten-free diet in celiac disease

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