Malabsorption is the inadequate absorption of nutrients from the gastrointestinal tract into systemic circulation, resulting from impaired digestion (maldigestion), damaged intestinal epithelium, or dysfunctional transport mechanisms. It leads to nutrient deficiencies despite adequate dietary intake.
Multiple mechanisms cause malabsorption: (1) Insufficient enzyme production—exocrine pancreatic insufficiency (lack of lipase, protease, amylase), brush border enzyme deficiency (lactase, sucrase); (2) Bile acid deficiency—impaired fat emulsification and absorption; (3) Intestinal epithelial damage—villous atrophy (celiac disease), inflammation (IBD), infections compromise absorptive surface area; (4) Bacterial overgrowth—SIBO causes premature nutrient metabolism and competition; (5) Rapid transit—diarrhea reduces contact time; (6) Unconjugated bilirubin—from insulin resistance inhibiting phase 2 liver conversion, prematurely shuts down digestive enzymes throughout GI tract.
Malabsorption is common but often unrecognized cause of nutrient deficiencies, fatigue, and immune dysfunction. Clinical signs: steatorrhea (fatty stools), weight loss, fat-soluble vitamin deficiencies (A, D, E, K), iron and B12 deficiency, muscle wasting, osteoporosis. Malabsorption cannot be overcome by simply increasing intake—root cause must be addressed. Assessment requires: comprehensive stool analysis (elastase for pancreatic function, fat content, undigested proteins), SIBO breath testing, inflammatory markers, and careful history (surgical history, medications, infections). Treatment targets underlying cause: pancreatic enzymes for EPI, bile acid support, gut barrier restoration, SIBO treatment, managing inflammation, addressing insulin resistance affecting bilirubin conjugation.
- Inadequate nutrient absorption despite adequate intake
- Causes: pancreatic insufficiency, bile deficiency, epithelial damage, SIBO, rapid transit
- Unconjugated bilirubin from insulin resistance prematurely inactivates digestive enzymes
- Signs: steatorrhea, weight loss, nutrient deficiencies, muscle wasting
- Fat-soluble vitamins (A, D, E, K) particularly affected
- Cannot be overcome by increasing intake alone—requires addressing root cause
- Common causes: celiac disease, IBD, pancreatitis, SIBO, surgical resection
- Stool elastase measures pancreatic enzyme production
- Chronic inflammation impairs intestinal absorption even without overt IBD
- Insulin resistance affects bilirubin conjugation indirectly impairing all digestion
- exocrine pancreatic insufficiency — EPI causes malabsorption through inadequate digestive enzyme production
- pancreatic enzymes — pancreatic enzyme deficiency (lipase, protease, amylase) causes maldigestion and malabsorption
- SIBO — small intestinal bacterial overgrowth causes malabsorption through bacterial nutrient competition
- celiac disease — celiac disease causes villous atrophy resulting in severe malabsorption
- IBD — inflammatory bowel disease damages intestinal epithelium causing malabsorption
- bile acids — bile acid deficiency impairs fat emulsification and absorption causing steatorrhea
- steatorrhea — steatorrhea (fatty stools) is classic sign of fat malabsorption
- nutrient deficiencies — malabsorption causes multiple nutrient deficiencies despite adequate intake
- vitamin D3 — vitamin D malabsorption common in fat malabsorption (fat-soluble vitamin)
- vitamin B12 — B12 malabsorption occurs with ileal damage, pancreatic insufficiency, or bacterial overgrowth
- iron — iron malabsorption common with intestinal inflammation or duodenal damage
- intestinal permeability — increased permeability often coexists with malabsorption from epithelial damage
- villous atrophy — villous atrophy reduces absorptive surface area causing severe malabsorption
- insulin resistance — insulin resistance inhibits bilirubin phase 2 conversion, shutting down enzyme activity causing malabsorption
- bilirubin — unconjugated bilirubin prematurely inactivates digestive enzymes throughout GI tract
- inflammation — intestinal inflammation impairs nutrient absorption through multiple mechanisms
- osteoporosis — chronic calcium and vitamin D malabsorption contributes to osteoporosis
- muscle wasting — protein malabsorption leads to muscle wasting and sarcopenia
- fatigue — nutrient deficiencies from malabsorption commonly cause chronic fatigue
- gut barrier — gut barrier restoration essential to reverse malabsorption from epithelial damage