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Six grams. That’s about one level scoop of PHGG, and it’s the daily amount that eased bloating in a 12-week trial of people with irritable bowel syndrome.
PHGG has built a quiet following among people whose guts don’t tolerate most fiber powders. It dissolves clear, barely changes the taste of a drink, and tends to cause less gas than many prebiotics, which is why it shows up so often in IBS conversations.
What is PHGG?
PHGG stands for partially hydrolyzed guar gum. It starts as guar gum, the thick soluble fiber from guar bean seeds, which is then treated with enzymes that cut its long chains into shorter ones.
Those shorter chains change everything about how it behaves. Native guar gum turns water into a heavy gel, while PHGG dissolves into a thin, clear liquid with almost no thickness at all.
The best-known brand is Sunfiber, and PHGG appears under other names in fiber blends and enteral feeding formulas. On labels, look for partially hydrolyzed guar gum, hydrolyzed guar gum or guar fiber.
Because it’s still a galactomannan, the same mannose and galactose sugars as guar gum, gut bacteria can ferment it. That’s what makes it a prebiotic fiber, a fiber that feeds beneficial gut microbes.
How PHGG behaves in your gut
PHGG passes through the stomach and small intestine without being digested. Because it’s so thin, it doesn’t slow digestion the way thick fibers do.
In the colon, bacteria ferment it gradually. That slower pace, compared with inulin or FOS, is one reason it’s often better tolerated by sensitive guts.
Fermentation produces short-chain fatty acids, small compounds that feed the cells lining the colon and help regulate water movement in the gut. PHGG also adds some bulk and water to stool.
That combination lets PHGG nudge stool in either direction. It can soften hard stool and help firm loose stool, which is why it’s studied for both constipation and diarrhea.
PHGG and its relatives
Several guar-based fibers sit on store shelves, and they’re easy to mix up:
- Native guar gum: the full-length fiber, used as a food thickener (E412). It forms a thick gel and ferments quickly.
- Partially hydrolyzed guar gum (PHGG): guar cut into shorter chains with enzymes. It’s thin and much gentler on the gut.
- Sunfiber: a widely studied brand of PHGG. Much of the research on PHGG used this ingredient.
- Fiber blends with PHGG: mixes that pair PHGG with other fibers or probiotics. The PHGG dose per serving can vary widely.
If a product just says “guar gum,” it’s most likely the native thickener rather than PHGG. Our guide to guar gum covers that form in detail.
PHGG for IBS: one trial, up close
The most-cited trial on PHGG for IBS was published in Nutrition & Metabolism in 2016. Researchers in Israel randomly assigned adults with IBS to 6 g of PHGG or a placebo each day for 12 weeks, then followed them for another 4 weeks.
121 people were randomized and 108 were included in the main analysis. They kept daily symptom diaries throughout, rating bloating, gas, pain and stool habits.
The diaries matter because IBS symptoms swing from day to day. A single clinic visit can catch someone on a good or bad week, while a daily record smooths that out.
Here’s how the main diary scores changed over the 12 weeks:
| Measure | PHGG 6 g a day | Placebo |
|---|---|---|
| Change in bloating score | −4.1 | −1.2 |
| Change in bloating plus gas score | −4.3 | −1.1 |
| Dropped out before the end | 22% | 49% |
Bloating improved more with PHGG than with placebo, and the combined score for bloating and gas did too. The benefit lasted at least 4 weeks after people stopped taking it.
The dropout gap stands out. Nearly half the placebo group quit, which hints that people taking PHGG found it worth sticking with, though dropouts also make the final numbers harder to read.
Beyond bloating, the scores for other symptoms and quality of life didn’t improve more than with placebo. PHGG also caused no significant side effects over the full 12 weeks.
The trial was modest in size and lost many participants along the way, especially in the placebo group. It points to PHGG as a helpful option for bloating rather than a fix for every IBS symptom.
If bloating and gut comfort are your main concerns, our gut health guides walk through how to adjust fiber without flaring symptoms.
PHGG benefits for constipation
Constipation is where PHGG has the broadest evidence. A 2017 review in the Journal of Functional Foods pooled 7 studies with 325 healthy volunteers and found PHGG increased bowel movement frequency compared with control.
The authors suggested that about 5 to 7 g a day was enough to see the effect, and they reported no adverse effects in the included studies. The studies were small and some weren’t randomized, so the review points in a direction rather than settling the question.
Most of the trials it pooled were short, often a few weeks long. That fits how people actually use PHGG, but it says little about taking it for years.
PHGG has also been tested in tube feeding formulas and for diarrhea. The idea is that the short-chain fatty acids it produces help the colon absorb water, which can firm loose stool.
If you’re adding a daily fiber powder for regularity, our fiber calculator shows how it fits into your overall fiber intake.
Is PHGG a low FODMAP fiber?
FODMAPs are fermentable carbohydrates that trigger symptoms in many people with IBS. Inulin and FOS, two popular prebiotics, are classic high FODMAP fibers.
PHGG is different. Monash University’s FODMAP researchers note that PHGG may be well tolerated and helpful for IBS with constipation and IBS with diarrhea, though they call for more studies.
That gentler profile is useful during the strict first phase of a low FODMAP diet, when many fiber sources get cut at once.
So PHGG is one of the few prebiotics people often keep during a low FODMAP diet. It’s commonly suggested as a low FODMAP fiber option, especially when psyllium feels too bulky.
PHGG compared with other fiber powders
Compared with psyllium, PHGG is thinner and easier to drink. Psyllium forms a thick gel that bulks stool more, and it has stronger evidence for lowering cholesterol.
Compared with inulin, PHGG ferments more slowly and tends to cause less gas. Inulin raises bifidobacteria strongly but often triggers bloating in IBS.
Compared with native guar gum, PHGG does less for blood sugar. A 2022 review in Foods noted that cutting guar into shorter chains lowers its thickness, and lower thickness can reduce the effect on post-meal blood sugar.
Here’s a quick rundown of how they stack up when you’re standing in front of the supplement shelf:
- Want something you can barely taste: PHGG dissolves fully in hot or cold drinks.
- Want the most bulk for constipation: psyllium adds more stool mass per gram.
- Want to feed bifidobacteria hard: inulin does it faster, at the cost of more gas.
- Want thicker meals and steadier blood sugar: native guar gum or psyllium thicken food, and PHGG doesn’t.
For a side-by-side look at fiber powders, our supplement comparison charts line up dose and texture for the common options.
PHGG side effects
Most people tolerate PHGG well. In the IBS trial, it caused no significant side effects at 6 g a day.
Like any fermentable fiber, a sudden jump in dose can bring gas or bloating. Starting low and building up over a week or two usually avoids that.
Some people notice a little rumbling in the first week, which usually settles as gut bacteria adjust. If it doesn’t, dropping back to the previous dose for a few days is the simplest fix.
PHGG has a long track record in hospital feeding formulas, where it’s given to people who are already unwell. That history doesn’t prove it’s right for everyone, but it does show the fiber is gentle enough for fragile guts.
Because it dissolves fully, PHGG carries less choking risk than thick, dry fibers. Still, take it mixed into a drink, and keep it a couple of hours away from medicines that need full absorption.
One way to start this week
Start with about half a serving, roughly 2 to 3 g, stirred into your morning coffee or a glass of water once a day. Hold that dose for a week and notice how your stools and bloating respond.
If you feel fine, move up to a full serving of around 5 to 6 g, the range used in most trials. Give it at least four weeks before deciding whether it helps.
Keep a simple note of two things each day: how bloated you feel on a scale of 1 to 10, and how your stools look. That mirrors what the IBS trial measured, and it turns a vague feeling into something you can compare week to week.
If nothing has shifted after a month at the full dose, PHGG may not be the right fiber for your gut. Psyllium or methylcellulose work through different routes and are worth trying next.
PHGG questions, answered
What is PHGG?
PHGG is partially hydrolyzed guar gum, a soluble prebiotic fiber made by breaking guar gum into shorter chains. It dissolves clear and is sold under brand names like Sunfiber.
Is PHGG good for IBS?
It may help, especially with bloating. A 2016 trial found 6 g a day eased bloating in adults with IBS over 12 weeks, though other symptoms didn’t change more than with placebo.
Is PHGG low FODMAP?
PHGG is generally considered a low FODMAP fiber. Monash University researchers note it may be well tolerated in IBS, unlike inulin and FOS.
Does PHGG help constipation?
Yes, modestly. A 2017 review of 7 studies found it increased bowel movement frequency, with about 5 to 7 g a day appearing effective.
What are PHGG side effects?
Side effects are usually mild, such as gas or bloating when starting. Trials have reported few problems at 5 to 6 g a day.
Is PHGG better than psyllium?
It depends on your goal. PHGG is gentler and easier to drink, while psyllium bulks stool more and has stronger cholesterol evidence.
How long does PHGG take to work?
Many people notice changes within one to two weeks. Trials generally ran for four to twelve weeks before measuring results.
Sources
- 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.” Nutrition & Metabolism. 2016. doi.org
- Kapoor MP, Sugita M, Fukuzawa Y, Okubo T. “Impact of Partially Hydrolyzed Guar Gum (PHGG) on Constipation Prevention: A Systematic Review and Meta-Analysis.” Journal of Functional Foods. 2017. doaj.org
- Collins L, Iacovou M. “Fibre Supplements & IBS.” Monash University FODMAP Blog. 2017. monashfodmap.com
- Giuntini EB, Sardá FAH, de Menezes EW. “The Effects of Soluble Dietary Fibers on Glycemic Response: An Overview and Futures Perspectives.” Foods. 2022. mdpi.com
