Benefits
Less bloating and gas
In a 12-week placebo-controlled trial in 108 analyzed adults with IBS, 6 g a day of PHGG lowered bloating and bloating-plus-gas journal scores, and the effect lasted 4 weeks after stopping. It did not change abdominal pain, stool frequency, overall IBS severity or quality of life.
Better tolerated than wheat bran as a fiber source
In a 12-week open-label trial in 188 adults with IBS, 5 g a day of PHGG and 30 g a day of wheat bran both improved pain and bowel habits, with no difference per protocol. More people switched from bran to PHGG than the reverse, and success by intention to treat was 60% versus 40%.
More normal stool form in adults with loose stools
In a 12-week placebo-controlled trial in 44 healthy Japanese adults with loose-stool tendencies, 5 g a day of PHGG moved stool form toward normal, with significant differences from placebo at some weeks. Stool frequency did not change. The product was the Sunfiber brand, and its maker funded the trial.
Prebiotic shift in gut bacteria
In the same trial, stool Bifidobacterium, Ruminococcus and Megasphaera rose and Bacteroides fell compared with placebo. These are changes in bacterial shares; the trial did not link them to a separate health outcome.
Less laxative use in older care-home residents
In a 4-week single-blind trial in 52 care-home residents with chronic constipation, 5 g a day of PHGG in water did not change bowel frequency or stool form compared with water alone. Residents taking PHGG did use less lactulose, senna and total laxatives in weeks 3 and 4.
Mechanism of action
Partial hydrolysis lowers viscosity
Native guar gum forms a thick gel. Partially hydrolyzed guar gum has shorter chains, so it dissolves in water as a non-gelling, low-viscosity fiber that can be stirred into drinks.
Fermented in the colon
PHGG reaches the colon, where bacteria ferment it. A review of earlier studies describes higher colonic short-chain fatty acids with PHGG, and stool bifidobacteria rose in a placebo-controlled trial.
Effects on stool form
In adults with loose stools PHGG moved stool form toward normal, and in an uncontrolled 4-week study of adults with constipation-type IBS, stool form and colonic transit time improved from baseline. How one fiber does both is not settled.
Clinical trials
Double-blind, placebo-controlled trial: 2-week run-in, 12 weeks of PHGG (3 g a day for the first week, then 6 g a day; the product was Sunfiber) or maltodextrin placebo, then 4 weeks of follow-up (Niv et al. 2016, Nutr Metab (Lond)).
121 adults with IBS randomized in Israel; 108 analyzed (49 PHGG, 59 placebo).
PHGG lowered journal bloating scores and combined bloating-and-gas scores versus placebo, and the effect lasted at least 4 weeks after stopping. It had no effect on abdominal pain, stool frequency, overall IBS severity or quality of life. Dropout was lower on PHGG (22% versus 49%).
Multicenter, randomized, open-label trial of PHGG 5 g a day versus wheat bran 30 g a day for 12 weeks, with the option to switch groups after 4 weeks (Parisi et al. 2002, Dig Dis Sci).
188 adults with IBS (139 women, 49 men) in Italy.
Both fibers improved abdominal pain and bowel habits, with no difference between groups per protocol. By intention to treat, success was 60% with PHGG versus 40% with bran, and 49.9% switched from bran to PHGG versus 10.9% the other way. The trial was not blinded.
Single-blind, randomized, controlled trial of 5 g a day of PHGG in 200 mL of water versus 200 mL of water alone for 4 weeks, with usual as-needed laxatives allowed (Chan et al. 2022, J Nutr Health Aging).
52 residents of four Hong Kong long-term care facilities with chronic constipation, mean age 83.9.
Bowel frequency and stool form did not differ between groups. Use of lactulose, senna and total laxatives was lower in the PHGG group in weeks 3 and 4. Adverse effects did not differ.