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Guar Gum / PHGG: The Complete Guide

Evidence Based

Guar gum is everywhere.  You can find it in your favorites foods and of course as ‘partially hydrolyzed guar gum’ in popular fiber supplements like Sunfiber.  And that’s not surprising when we see just how well it can work for a range of digestive and overall health issues.  But there’s a lot of hot air out there too.  So let’s sort the fact from the fiction.  Let’s go!

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What is it? Benefits Side Effects Summary & Verdict
Researched & Written by
Bailey Franzen MS, RDN
Bailey Franzen MS, RDN
Registered Dietitian Nutritionist
Carolyn Quijano MS, RDN
Carolyn Quijano MS, RDN
Registered Dietitian Nutritionist

Edited by Digest Life team

Last Updated: 7 April 2021

What is Guar Gum / PHGG?

Guar gum is the endosperm portion from the seeds of the leguminous guar plant (with the scientific name of Cyamopsis tetragonolobus). The plant originated from India, West Pakistan, South Africa, Australia, and the United States.

If you read food labels, you have probably seen guar gum at some point listed in the ingredients. It is used as a stabilizer and thickener because of its impressive binding abilities.

Guar gum has almost eight times the thickening power of cornstarch1 and is in various products such as juice, ice cream, sauce, ketchup, syrups, salad dressings, etc.2

Different gums like xanthan gum, acacia gum, or locust bean gum are used in food production for similar reasons.

Guar gum has beneficial physiological effects; however, its high viscosity and water-binding capabilities make it difficult to incorporate into food products in the amount necessary to use as dietary fiber.3 Guar gum, needed in the appropriate dosage, may cause choking due to its swelling properties.4

To remedy this, guar gum goes through a process called enzymatic hydrolysis (basically semi-breaking down the carbohydrate structure). This process results in what we know to be guar fiber, or more commonly, partially hydrolyzed guar gum (PHGG).

This process turns viscous, soluble, and binding guar gum into a non-viscous soluble dietary fiber that is easily tolerated by the gut.1,4 PHGG has shown to be consumed at doses as high as 40 g per day without significant side effects.1

What are the benefits of PHGG, aka Sunfiber?

1.  Bowel function – constipation, diarrhea, IBS & SIBO

Overall, PHGG can be considered as an effective fiber supplement for promoting digestive health. It is effective in the prevention and symptom treatment of constipation, diarrhea, and IBS.

PHGG has also been used in conjunction with antibiotics to aid the eradication of small intestinal bacterial overgrowth (SIBO).5 However, more research is needed to support the use of PHGG for this purpose.


Several clinical trials show an improvement in constipation when using PHGG.4 Generally, constipation is defined by having less than 3 bowel movements a week; however, this definition poorly captures the experience of constipation-sufferers. For example, someone with constipation may have a bowel movement daily but have incomplete evacuations, difficulty passing stool, or pain.

When consuming PHGG, stool consistency was changed from hard to normal, making stool easier to pass. The frequency in defecation, fecal weight, and fecal moisture increased, while the fecal pH and abdominal pain associated with chronic constipation decreased.4, 6


Diarrhea, defined as having more than 3 bowel movements per day, improved with PHGG supplementation. The studies available are primarily in tube-fed patients or children. Still, results are indicative of symptom relief when supplementing with PHGG.

The studies identified symptom relief as a decrease in diarrhea incidence, diarrhea duration, and overall stool output. A study with healthy participants suggests the prevention of sugar-alcohol-induced diarrhea with 5 to 10 g/d of PHGG.6


We see that PHGG has a dual action to improve both constipation and diarrhea, so it’s only natural that it could be helpful for those who suffer from Irritable Bowel Syndrome (IBS).

IBS has three subtypes, D (diarrhea), C (constipation), and M (mixed type). IBS-C is associated with an overproduction of methane.7 In a study conducted on 40 methane-producing adults, there was a decrease in the presence of methane when taking PHGG.

Multiple clinical studies suggest that PHGG at a daily dose of 5 g per day effectively decreases symptoms and improves the quality of life in IBS patients. The effectiveness of PHGG in the treatment of IBS symptoms is likely because PHGG slowly ferments in the colon, which prevents rapid gas production and bloating.4


It is thought that a significant number of people suffer both from SIBO and IBS. SIBO is an excess or presence of abnormal types of bacteria in the small intestine.7 Rifaximin is a known antibiotic treatment of SIBO. A study aimed at determining if the addition of PHGG to rifaximin would help eradicate SIBO concluded that the combination of rifaximin and PHGG provided a synergistic action in helping to eradicate SIBO when compared to rifaximin treatment alone. It is possible that the addition of PHGG helped aid in intestinal clearance and microflora balance.5 These results are hopeful for the SIBO world, as SIBO-sufferers tend to deal with multiple relapses.

PHGG and Gut Health
Study Result Dosage
↓ Constipation by increasing defecation frequency and moisture content and decreasing ph in feces 5 g per day for up to 6 weeks4
↓ Diarrhea in 45 tube-fed fed patients 20-30 g per day (approximation)4
Prevention of diarrhea induced by maltitol and lactitol in 35 healthy people 5-10 g per day4
↓ IBS symptoms (abdominal pain, bloating, bowel habits) and improve quality of life in those with IBS 5-6 g per day for up to 12 weeks4
↓ methane in feces and IBS symptoms in a study with 40 methane-producing adults 5 g per day for up to 4 months4
↑ eradicating SIBO with the combination of antibiotics and PHGG in comparison to antibiotics  alone 5 g per day for 10 days5

2.  Heart Health

An adequate amount of dietary fiber is a known benefit for heart health due to its cholesterol-lowering effects. Fibers that have a high water-holding and gel-forming capacity (viscosity) are most associated with a cholesterol-lowering effect.

Viscosity is decreased in PHGG due to the processing of this fiber. Interestingly, despite the low viscosity, PHGG maintains cholesterol-lowering effects and has been found to improve blood lipid panels.1

PHGG and Heart Health
Study Result Dosage
↓ serum cholesterol in healthy adults 15-36 g per day for 2-4 weeks1

3.  Diabetes

PHGG appears to positively affect blood sugar levels, both in people with diabetes and healthy people. The studies on PHGG and blood sugar levels had different effects on the timing of effectiveness. For example, one study had results that showed decreased blood sugar levels at 60 and 90 minutes after a meal, where another study had significantly lower blood sugar levels only at 2 hours after a meal.

It’s difficult to say whether the differing results were due to study design or if the low viscosity of PHGG plays a role. That being said, it’s clear that supplementing with PHGG at meals does cause a decrease in blood sugar levels. While other fiber supplements (like psyllium) may be more effective at decreasing blood sugar levels, PHGG still has some positive effects.1

PHGG and blood sugar levels
Study Result Dosage
↓ blood sugar levels at 60 am 90 minutes after glucose solution with PHGG 15 g per day with meals1
↓ blood sugar levels at 120 minutes after breakfast 6 g per day at breakfast1

4.  Changes in the microbiome

Through various studies, PHGG has positively affected the microbiome by increasing short-chain fatty acid production and altering types of bacterial growth. The SCFAs that increased with PHGG supplementation were acetate and butyrate.5

The bacteria changes were an increase in bifidobacteria and ruminococcus and a decrease in the number of bacteroides.1,5,8 Research within the microbiome is still in its early stages, and study results vary. This is likely due to the individuality of each microbiome in each study participant.2

Benefits of acetate

  • Anti-inflammatory effects
  • Increases blood flow to the colon
  • Used to help produce butyrate when microbes cross-feed
  • An energy source for muscle and brain tissue
  • Lowers pH of the colon
    • Increases mineral absorption and blocks growth of pathogens9

Benefits of butyrate

  • A preferred energy source for colon epithelial cells
  • Lowers pH of the colon
    • Helps to increase mineral absorption and blocks the growth of pathogens
  • Promotes the health and proliferation of normal colon epithelial cells
  • It prevents colorectal cancer proliferation and promotes colorectal cancer cell death
  • Protects against colon cancer and colitis9

Bifidobacterium species have been shown to:

  • Modulate the immune system
  • Have an anti-carcinogenic effect
  • Secrete antimicrobial compounds; inhibit the growth of pathogenic bacteria
  • Increase resistance to infection
  • Produce SCFAs such as lactate and acetate while cross-feeding with butyrate producers
  • Produce certain vitamins10,11

Ruminococcus species have been shown to:

  • Breakdown plant-based cellulose and ferment them
  • Produce acetate12
PHGG and Microbiome Changes
Effect Dose
↑ butyrate and acetate in 20 healthy individuals 5 g, 3x/day for 9 weeks2
↑ bifidobacterium and ruminococcus in people with IBS-D-like tendencies 5g/day for 12 weeks8
↑ bifidobacterium in healthy adults 6-12 g/day for 2 weeks8

What are potential side effects of guar fiber?

PHGG is reported as a highly tolerable fiber supplement. In the studies reviewed, some adverse effects like mild gas were mentioned when beginning supplementation.

When increasing fiber intake, there is always a risk of bloating, flatulence, or mild GI distress. Introducing fiber slowly and the addition of water can help to prevent potential adverse effects.

Summary & Verdict

  • Partially hydrolyzed guar gum (PHGG) is created by enzymatically breaking down the seed portion of guar gum so that the fiber can be more broadly utilized for health benefits.
  • PHGG is a soluble, non-viscous, poorly fermented fiber and is highly tolerated by most people, even those with a sensitive gut.
  • PHGG has repeatedly shown to benefit those who suffer from diarrhea, constipation, and IBS.
  • PHGG has improved lipid profiles and blood sugar levels in several studies.
  • Supplementing PHGG has been shown to change the microbiome by supporting beneficial bacteria and short-chain fatty acid (SCFA) production.

PHGG seems to be a superstar in the world of gut health, helping with diarrhea, constipation, and IBS-related symptoms. It will be exciting to see where PHGG lands in the treatment of IBS and SIBO, as well as the effects on the ever-evolving microbiome.


  1. Sungsoo Cho S, Samuel P. Fiber Ingredients: Food Applications And Health Benefits. Boca Raton: CRC Press; 2009:79-120.
  2. Reider S, Moosmang S, Tragust J et al. Prebiotic Effects of Partially Hydrolyzed Guar Gum on the Composition and Function of the Human Microbiota—Results from the PAGODA Trial. Nutrients. 2020;12(5):1257. doi:10.3390/nu12051257
  3. Mudgil D, Barak S, Patel A, Shah N. Partially hydrolyzed guar gum as a potential prebiotic source. Int J Biol Macromol. 2018;112:207-210. doi:10.1016/j.ijbiomac.2018.01.164
  4. Rao T, Quartarone G. Role of guar fiber in improving digestive health and function. Nutrition. 2019;59:158-169. doi:10.1016/j.nut.2018.07.109
  5. Furnari M, Parodi A, Gemignani L et al. Clinical trial: the combination of rifaximin with partially hydrolysed guar gum is more effective than rifaximin alone in eradicating small intestinal bacterial overgrowth. Aliment Pharmacol Ther. 2010;32(8):1000-1006. doi:10.1111/j.1365-2036.2010.04436.x
  6. Slavin J, Greenberg N. Partially hydrolyzed guar gum. Nutrition. 2003;19(6):549-552. doi:10.1016/s0899-9007(02)01032-8
  7. Shah A, Talley N, Jones M et al. Small Intestinal Bacterial Overgrowth in Irritable Bowel Syndrome: A Systematic Review and Meta-Analysis of Case-Control Studies. American Journal of Gastroenterology. 2020;115(2):190-201. doi:10.14309/ajg.0000000000000504
  8. 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. doi:10.3390/nu11092170
  9. Rivière A, Selak M, Lantin D, Leroy F, De Vuyst L. Bifidobacteria and Butyrate-Producing Colon Bacteria: Importance and Strategies for Their Stimulation in the Human Gut. Front Microbiol. 2016;7. doi:10.3389/fmicb.2016.00979
  10. Alarifi S, Bell A, Walton G. In vitro fermentation of gum acacia – impact on the faecal microbiota. Int J Food Sci Nutr. 2018;69(6):696-704. doi:10.1080/09637486.2017.1404970
  11. LeBlanc J, Chain F, Martín R, Bermúdez-Humarán L, Courau S, Langella P. Beneficial effects on host energy metabolism of short-chain fatty acids and vitamins produced by commensal and probiotic bacteria. Microb Cell Fact. 2017;16(1). doi:10.1186/s12934-017-0691-z
  12. La Reau A, Suen G. The Ruminococci: key symbionts of the gut ecosystem. Journal of Microbiology. 2018;56(3):199-208. doi:10.1007/s12275-018-8024-4