Randomized, Double-Blind Placebo-Controlled Trial to Assess the Effect of Probiotics on Irritable Bowel Syndrome in Veterans With Gulf War Illness
Background: Many veterans who served in Operation Desert Storm (August 1990 to March 1991) experienced a complex of symptoms of unknown etiology called Gulf War illness (GWI), which significantly impacts the health and quality of life (QOL) and may have contributed to irritable bowel syndrome (IBS).
Methods: We performed a prospective, double-blind placebo-controlled study to determine the efficacy of the multistrain De Simone Formulation probiotic containing 8 strains of bacteria on symptoms of IBS and GWI. Veterans of Operation Desert Storm who had IBS and ≥ 2 nonintestinal symptoms of GWI were included. The primary study endpoint was change in bowel symptom score. The secondary endpoints were mean change in symptoms, QOL, and extra-intestinal and posttraumatic stress disorder (PTSD) symptoms.
Results: A total of 101 Gulf War veterans with IBS and GWI were screened at the Veteran Affairs Medical Center in Salt Lake City, Utah. The study was completed by 53 veterans; 47 (89%) were male with a mean (SD) age of 55 (8) years. The probiotic did not improve IBS symptoms or other extra-intestinal symptoms common to IBS and GWI.
Conclusions: Our study did not demonstrate statistically significant improvement in IBS symptoms or QOL after treatment with the probiotic. We also did not find any improvement in symptoms of GWI or PTSD.
An individual’s response to probiotics may depend on the subtype of IBS. However, most of the studies, like ours, included groups of all subtypes. It may be that probiotics are more effective in patients with moderate-to-severe symptoms. Most of our patients had milder symptoms, and we cannot discount how subjects with more severe disease may have responded to the drug. Interestingly, one study demonstrated that Lactobacillus was more effective in patients with moderately severe abdominal pain compared with mild symptoms.44
In our study, the probiotic did not improve PTSD symptoms or other extra-intestinal symptoms common in IBS and GWI. Similar to our study, Wong and colleagues did not find significant improvement of psychological and sleep scores after treatment with VSL#3.6 Similarly, there is evidence that alteration in gut microbiota is associated with health and diseases, but what specific alterations occur and whether they can be improved with probiotics remains unknown.45
Limitations
The inconsistent response to probiotics in various studies may be due to IBS heterogeneity. Furthermore, there are demographic differences between Gulf War veterans and patients enrolled in other studies: Gulf War veterans are predominantly male, many were deployed abroad and had a history of gastroenteritis during deployment, and were exposed to stressful situations.46 These factors may be involved in triggering or maintaining IBS in Gulf War veterans. A further limitation of our randomized trial is the relatively small sample size.
Conclusions
This study did not demonstrate statistically significant improvement in symptoms of IBS or improvement in QOL after treatment with a multistrain probiotic. We also did not find any improvement in symptoms of GWI or PTSD. There was no difference in psychological scores between the placebo and treatment groups, and it is unlikely that psychological factors confounded the response to treatment in this study.
The effectiveness of a probiotic may depend on the baseline gut microbiome of the individual and depend on the strain, amount, and frequency of bacteria used. A lack of response of the probiotics does not exclude gut viruses and fungi having a role in exacerbating GWI symptoms. It is also possible that the bacteria present or the dose of the probiotic used was not sufficient to improve symptoms. So far, the definitive benefit of probiotics has been demonstrated for only a few preparations, and none are approved by the US Food and Drug Administration for any disease. More research is needed to determine whether probiotics have any role in the treatment of IBS and GWI.
Acknowledgments
AKT received grant support from the US Department of Veterans Affairs and the US Department of Defense (W81XWH-10-1-0593, W81XWH-15-1-0636). We thank Keith G. Tolman, MD, for assistance in editing the initial proposal and for periodic consultation. We thank the manufacturer of the probiotic for supplying the active drug and the placebo. The manufacture of the probiotic had no role in the design and conduct of the study, analysis and interpretation of the data, and in the preparation of the manuscript.
