Randomized Clinical Study

Partially Hydrolyzed Guar Gum (PHGG) Versus Placebo in the Treatment of Patients With Irritable Bowel Syndrome

E. Niv; A. Halak; E. Tiommny; H. Yanai; H. Strul; T. Naftali; N. Vaisman


Nutr Metab. 2016;13(10) 

In This Article


This prospective, randomized, double blind placebo-controlled study on the effects of 12 weeks of administration of 6 g/day PHGG on the clinical symptoms of IBS patients revealed that PHGG produced a significant improvement on bloating and gasses symptoms of IBS patients compared to placebo. Its use was not associated with any significant side effects. The effect of this prebiotic lasted at least four weeks after the cessation of its ingestion. PHGG did not, however, have any effect on abdominal pain, stool frequency, or QOL. Therefore, the results of this study support the administration of 6 g/day PHGG for IBS patients with bloating and gasses.

The administration of PHGG in IBS patients has been reported by others. Giaccari et al[24] administered PHGG to 134 IBS patients in addition to a balanced diet and found a positive effect of PHGG on various IBS symptoms. Their study, however, was observational and not randomized, there was no placebo group, and PHGG was taken as a supplementation to a balanced diet. Paresi et al[22] treated 188 IBS patients with a high–fiber diet supplementation (30 g/day of wheat bran) or PHGG (5 g/day) for 12 weeks. Improvements in core IBS symptoms were observed with both the bran and PHGG, but the latter was better tolerated and preferred by patients. That crossover study was very interesting, but the lack of a placebo group and a follow-up period posed important limitations. The same authors[23] published an important paper in which they compared the effects of PHGG administered at two dosages (5 and 10 g/day) for 3 months in patients with IBS, followed by three months of follow-up. The symptoms of IBS and QOL improved significantly for the patients in both dosage groups. However, this positive effect was significantly reduced during the three-month follow-up.

This study's major strength lies in its being the first prospective, randomized, double blind placebo-controlled investigation of the effect of PHGG in the setting of IBS. The profound placebo effect on IBS symptoms (ranging from 20–50%) is well-established.[5,6] In the current study, the net placebo effect was about 20%. In fact, every significant study regarding IBS should be placebo-controlled. Therefore a proven statistically significant effect on bloating and gasses over placebo in our study has an important significance. One weakness of the current study is the relatively high dropout rate, although most of the dropouts were in the placebo group (47.5%) compared with the PHGG group (23.5%), supporting a positive effect of PHGG. The follow-up period in our study was four weeks, which is adequate, but a longer period would be able to establish whether PHGG treatment should be episodic or continuous.

This study did not focused on the mechanism of PHGG influence on the GI tract of IBS patients. Previous studies proved an ability of PHGG to act as a prebiotic fiber and influence the microbiota. For example, in two clinical studies (one –in constipated women and the second one in healthy volunteers) several weeks of PHGG administration resulted in the increase of Bifidobacterium and Lactobacillus spp and the decrease of Clostridium spp, Enterobacteriaceae and Streprococcaceae.[9,11] Moreover, in vitro fermentation of PHGG results in an active production of short chain fatty acids, which are important for colon health as a primary energy source of colonocytes.[31] Therefore, presumably the mechanisms of PHGG impact on the GI tract of IBS patients are through a microbiota change and a positive stimulating effect on colonocytes. However, the exact mechanism of PHGG influence is still unknown and should be a subject of further research.