title: Combat-training increases intestinal permeability, immune activation and gastrointestinal symptoms in soldiers.
abstract: BACKGROUND
  Gastrointestinal (GI) symptoms are common in soldiers in combat or high-pressure operational situations and often lead to compromised performance. Underlying mechanisms are unclear, but neuroendocrine dysregulation, immune activation and increased intestinal permeability may be involved in stress-related GI dysfunction.
  
  
  OBJECTIVE
  To study the effects of prolonged, intense, mixed psychological and physical stress on intestinal permeability, systemic inflammatory and stress markers in soldiers during high-intensity combat-training.
  
  
  METHODS
  In 37 male army medical rapid response troops, GI symptoms, stress markers, segmental intestinal permeability using the 4-sugar test (sucrose, lactulose, mannitol and sucralose) and immune activation were assessed during the 4th week of an intense combat-training and a rest period.
  
  
  RESULTS
  Combat-training elicited higher stress, anxiety and depression scores (all P < 0.01) as well as greater incidence and severity of GI symptoms [irritable bowel syndrome symptom severity score (IBS-SSS), P < 0.05] compared with rest. The IBS-SSS correlated with depression (r = 0.41, P < 0.01) and stress (r = 0.40, P < 0.01) ratings. Serum levels of cortisol, interleukin-6, and tumour necrosis factor-α, and segmental GI permeability increased during combat-training compared with rest (all P < 0.05). The lactulose:mannitol ratio was higher in soldiers with GI symptoms (IBS-SSS ≥75) during combat-training than those without (IBS-SSS <75) (P < 0.05).
  
  
  CONCLUSIONS
  Prolonged combat-training not only induces the expected increases in stress, anxiety and depression, but also GI symptoms, pro-inflammatory immune activation and increased intestinal permeability. Identification of subgroups of individuals at high-risk of GI compromise and of long-term deleterious effects of operational stress as well as the development of protective measures will be the focus of future studies.
authors: Neurogastroenterology Research Unit, Department of Medicine, National University of Singapore, Singapore.
authors: X
authors: X
authors: Li
authors: E M
authors: EM
authors: Kan
authors: J
authors: J
authors: Lu
authors: Y
authors: Y
authors: Cao
authors: R K
authors: RK
authors: Wong
authors: A
authors: A
authors: Keshavarzian
authors: C H
authors: CH
authors: Wilder-Smith
mesh_terms: D001008:Anxiety Disorders / Q000209:etiology; D044466:Asian People; D003866:Depressive Disorder / Q000209:etiology; D005767:Gastrointestinal Diseases / Q000209:etiology* / Q000276:immunology; D006801:Humans; D007107:Immune System / Q000502:physiology*; D007413:Intestinal Mucosa / Q000378:metabolism*; D008297:Male; D008889:Military Personnel; D010539:Permeability; D010806:Physical Education and Training; D011446:Prospective Studies; D012044:Regression Analysis; D012846:Singapore; D013312:Stress, Physiological; D013315:Stress, Psychological; D011795:Surveys and Questionnaires; D055815:Young Adult