Galactooligosaccharide supplementation reduces stress-induced gastrointestinal dysfunction and days of cold or flu: a randomized, double-blind, controlled trial in healthy university students

Am J Clin Nutr. 2011 Jun;93(6):1305-11. doi: 10.3945/ajcn.111.014126. Epub 2011 Apr 27.


Background: Acute psychological stress induced by academic exams is associated with dysregulated gastrointestinal and immune function.

Objective: We examined whether supplementation with galactooligosaccharides reduced gastrointestinal dysfunction and the percentage of days with cold or flu in academically stressed undergraduate students.

Design: In a randomized, double-blind study, subjects (n = 427) received 0, 2.5, or 5.0 g galactooligosaccharides for 8 wk around the time of fall final exams. Levels of stress and cold or flu symptom intensity (SI; 0 = not experiencing to 3 = severe) were recorded daily. The SI from 9 cold or flu symptoms was summed with 1 d of cold or flu defined as a sum >6. The Gastrointestinal Symptom Response Scale was completed weekly.

Results: Stress was positively related to diarrhea, indigestion, and reflux syndromes and with abdominal pain, average daily cold or flu SI score, and the percentage of days with cold or flu. Gastrointestinal symptom scores for diarrhea (P = 0.0298), constipation (P = 0.0342), abdominal pain (P = 0.0058), and indigestion (P = 0.0003) syndromes were lower after galactooligosaccharide supplementation. The cold or flu SI score was affected by galactooligosaccharides and stress (P < 0.0001); 2.5 g was associated with a lower SI score across all levels of stress, but 5.0 g was protective only at lower levels of stress. The percentage of days with cold or flu was associated with galactooligosaccharides within different body mass index categories (P = 0.0002), wherein a 40% reduction in the percentage of days with cold or flu was observed in normal-weight individuals with 5.0 g galactooligosaccharides. This effect was not observed in overweight or obese individuals.

Conclusions: Acute psychological stress was directly related to symptoms of gastrointestinal dysfunction and cold or flu. Galactooligosaccharide supplementation reduced these symptoms and the number of days with cold or flu. This trial was registered at as NCT01137760.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abdominal Pain / drug therapy*
  • Abdominal Pain / etiology
  • Adult
  • Body Mass Index
  • Common Cold / drug therapy*
  • Common Cold / etiology
  • Dietary Supplements
  • Double-Blind Method
  • Female
  • Galactose / therapeutic use*
  • Gastrointestinal Diseases / drug therapy
  • Gastrointestinal Diseases / etiology
  • Humans
  • Influenza, Human / drug therapy*
  • Influenza, Human / etiology
  • Male
  • Oligosaccharides / therapeutic use*
  • Prebiotics*
  • Reference Values
  • Stress, Psychological / complications*
  • Students
  • Universities
  • Young Adult


  • Oligosaccharides
  • Prebiotics
  • Galactose

Associated data