Introduction

Emerging evidence suggests a possible role for γ-aminobutyric acid (GABA) in the development of irritable bowel syndrome with diarrhea (IBS-D), as well as its possible therapeutic use.

Aims & Methods

This study primary aimed to assess the efficacy of a GABA-based supplement in patients with IBS-D in terms of improvement in quality of life. Secondary aims included assessing its impact on psychological wellbeing and gastrointestinal symptoms.
In this double-blind, placebo-controlled, single center, crossover pilot study, 20 IBS-D patients were randomized to receive a food supplement containing GABA and Melissa officinalis or a placebo, at the dosage of one tablet three times daily for two treatment periods of 4 weeks each, separated by a 2-week washout period. Before and after each treatment, patients were assessed through:

• IBS Symptom Severity Scale (IBS-SSS). Responders were those with a ≥50-point reduction in IBS-SSS.
• Short Form Health Survey 36 (SF-36) multidimensional questionnaire.
• Hospital Anxiety and Depression Scale (HADS).

Pre- and post-treatment values were compared using a paired t-test; treatment comparisons used mixed models analysis.

Results

Eighteen patients completed the study (10 females, age 30.3±10.3 years).
A significant reduction of IBSS-SSS total score, as well as in all individual items, was observed in the GABA group (Table 1). A reduction of at least 50 points was achieved in 66.7% of patients treated with GABA and in 33.3% of those treated with placebo. Mixed models analysis showed a significant improvement with GABA compared to placebo in the IBS-SSS total score (p=0.01) and in the «Bowel satisfaction» item (p=0.005).
A significant improvement on the «Mental health» (p=0.007) and «Bodily pain» (p=0.09) items and in the mental composite score (MCS) of the SF-36 (0.037, Table 1) was observed with GABA. Mixed models analysis showed a significant improvement with GABA compared to placebo in the «Physical limitations» (p=0.033) and «Emotional limitation» (p=0.028) domains of SF-36.
GABA supplementation significantly improved the «HAD-Anxiety» score compared to baseline (6.7±3.0 Vs 5.1 ±2.7, p=0.02, Table 1) even though at mixed model analysis there was no significant effect.

Table 1. Comparison between pre- and post-treatment in placebo and GABA arms of the study.

Conclusion

In this pilot study, GABA and Melissa officinalis supplementation showed a higher overall improvement in IBS-D symptoms (IBS-SSS total) and particularly in bowel habits satisfaction compared to placebo. GABA supplementation was superior to placebo in improving daily functioning, especially regarding physical and emotional limitations in IBS-D patients. GABA may be a valuable therapeutic option deserving further investigation in larger trials.

Disclosure

No conflicts of interest to declare