Partially hydrolyzed guar gum (PHGG): what the research says

Partially hydrolyzed guar gum won't win any naming contests. It usually goes by PHGG, and on ingredient lists you may see it under a brand name. It's also one of the more interesting fibers for people whose guts tend to protest when they eat more fiber.

Here's what the human studies found, how strong that evidence is, and where the gaps still are.

What PHGG is

PHGG starts as guar gum, which comes from guar beans. The gum is broken into shorter pieces, which is what "partially hydrolyzed" means. The result is a water-soluble fiber that doesn't form a gel (Polymeros et al., 2014), so it can be stirred into drinks and soft foods without turning them thick.

Bloating and IBS: the two key trials

PHGG versus wheat bran. In a multicenter trial, 188 adults with IBS, 139 of them women, were randomly assigned to 30 grams of wheat bran or 5 grams of PHGG a day for 12 weeks. After four weeks, people could switch groups based on how they felt. Almost half of the bran group (49.9%) switched to PHGG, while 10.9% switched from PHGG to bran (Parisi et al., 2002).

Both fibers improved abdominal pain and bowel habits among people who stayed in their assigned group. But when everyone who started was counted, success rates were 60% with PHGG and 40% with bran. The authors concluded that PHGG was better tolerated and preferred. One limitation: this was an open trial, so participants knew what they were taking.

PHGG versus placebo. A double-blind trial randomized 121 people with IBS to 6 grams of PHGG a day or a placebo for 12 weeks, with 108 included in the final analysis. PHGG improved bloating scores in symptom diaries compared with placebo (a change of -4.1 versus -1.2), as well as a combined bloating and gas score. The effect lasted for at least four weeks after people stopped taking it (Niv et al., 2016).

That trial is also a good example of honest limits. PHGG didn't change other diary symptoms, overall IBS severity scores or quality of life. There were no significant side effects, and fewer people dropped out on PHGG (22.45%) than on placebo (49.15%).

Constipation

In a study of adults with chronic constipation, 49 people took PHGG daily for four weeks and 39 completed the study. Colonic transit time fell from 57.28 to 45.63 hours on average, with a bigger drop in people whose transit was slow to begin with. Weekly bowel movements increased, straining decreased, stool form improved, and people had fewer days with laxative use and abdominal pain (Polymeros et al., 2014).

There was no placebo group, so some of that improvement could reflect other factors. It's encouraging, but less conclusive than a controlled trial.

Loose stools, too

PHGG doesn't only push in one direction. In a double-blind, placebo-controlled trial, 44 healthy adults with an average age of 41.9 who tended toward loose stools took PHGG or a placebo for three months. PHGG significantly normalized stool form compared with placebo, without changing how often people went (Yasukawa et al., 2019).

What it does to gut bacteria

In that same trial, PHGG increased Bifidobacterium (Yasukawa et al., 2019). A separate small study in 10 healthy volunteers who took 6 grams a day for two weeks found increases in Bifidobacterium and in several groups of bacteria that produce butyrate, a short-chain fatty acid (Ohashi et al., 2015).

These are interesting signals, but a change in bacteria isn't the same as a change in how you feel. The symptom trials above are more useful when you're deciding whether to try it.

What the evidence doesn't show yet

• The trials are small to mid-sized, and some were open-label or had no placebo group.
• Most were done in people with IBS or constipation, not in the general population.
• None of these trials focused on women in perimenopause or menopause.
• Doses were modest, 5 to 6 grams a day in the IBS trials, so they don't tell us much about larger amounts.

If you want to try PHGG

1. Start with about half the label amount for the first week.
2. Stir it into a drink or soft food you already have every day, so it becomes routine.
3. Work up to the full label amount over a week or two.
4. Give it at least four weeks, and rate your bloating and stool form a few times a week.
5. Keep everything else the same during the trial if you can, so you know what's responsible for any change.

If you're looking for a PHGG product, noonlife's Gentle Fiber contains 6 grams of Sunfiber® PHGG per unflavored stick, with no inulin, psyllium or sugar.

As with any fiber, see your doctor first if your symptoms are new or come with red flags like blood in your stool, unexplained weight loss, anemia or bloating most days.

Sources

1. Polymeros D, Beintaris I, Gaglia A, et al. Partially hydrolyzed guar gum accelerates colonic transit time and improves symptoms in adults with chronic constipation. Dig Dis Sci. 2014;59(9):2207-14. PMID 24711073
2. Parisi GC, Zilli M, Miani MP, et al. High-fiber diet supplementation in patients with irritable bowel syndrome (IBS): a multicenter, randomized, open trial comparison between wheat bran diet and partially hydrolyzed guar gum (PHGG). Dig Dis Sci. 2002;47(8):1697-704. PMID 12184518
3. Niv E, Halak A, Tiommny E, et al. Randomized clinical study: partially hydrolyzed guar gum (PHGG) versus placebo in the treatment of patients with irritable bowel syndrome. Nutr Metab (Lond). 2016;13:10. PMID 26855665
4. Yasukawa Z, Inoue R, Ozeki M, et al. Effect of repeated consumption of partially hydrolyzed guar gum on fecal characteristics and gut microbiota: a randomized, double-blind, placebo-controlled, and parallel-group clinical trial. Nutrients. 2019;11(9):2170. PMID 31509971
5. Ohashi Y, Sumitani K, Tokunaga M, Ishihara N, Okubo T, Fujisawa T. Consumption of partially hydrolysed guar gum stimulates bifidobacteria and butyrate-producing bacteria in the human large intestine. Benef Microbes. 2015;6(4):451-5. PMID 25519526

This article is for general information and isn't medical advice. Check with your healthcare provider before starting a fiber supplement, especially if you have a digestive condition or take medication.