Partially Hydrolyzed Guar Gum (PHGG)

What it is

Guar gum comes from milling the endosperm of the guar seed. Its main polysaccharide is galactomannan, which is highly viscous, so the intact gum is used to thicken and stabilize foods.^[4] PHGG is made by treating guar gum with a galactomannan-splitting enzyme from the mold Aspergillus niger.^[2] Shorter chains mean far less thickening: PHGG has low viscosity and can be added to beverages and enteral formulas as a source of fiber.^[1]

That change also changes how it behaves in the gut. Intact guar gum is viscous and highly fermentable, and the 2005 fiber report notes it has little effect on stool bulk.^[4] A two-part review classes PHGG as non-gelling and readily fermented, which means it does not hold water through the bowel the way psyllium's gel does, and fermentation can produce gas.^[5][3] The review's author worked for a company that sells a psyllium product.

For labeling, FDA lists guar gum among the isolated fibers it has found to have physiological effects beneficial to health, so it counts toward "dietary fiber" on a Nutrition Facts label.^[6] The glossary entry for PHGG has the short version. Replenish uses PHGG as its only fiber, alongside sodium, potassium and magnesium.

How much adults need

There is no intake target for PHGG itself. The reference value is for total fiber, the sum of fiber in food and isolated fibers such as PHGG.^[4]

Source: Institute of Medicine, Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2005), Chapter 7.^[4] AI = Adequate Intake; UL = Tolerable Upper Intake Level. ND = not determined: the committee set no UL for dietary fiber or for individual isolated fibers.

Amount in Replenish: confirmed at launch

The AI is built from a ratio, 14 g of fiber per 1,000 kcal, the intake linked with lower coronary heart disease risk in large cohort studies, multiplied by typical energy intake for each group.^[4] The report notes that people who eat less than the median energy intake need proportionally less.^[4] The Dietary Guidelines use the same 14 g per 1,000 calories, and the Daily Value on labels is 28 g.^[7][8] Most adults fall short: median dietary fiber intakes in the report were 16.5 to 17.9 g a day for men and 12.1 to 13.8 g for women.^[4] What that means when appetite is small is worked through in how much fiber a day on a GLP-1.

What the evidence says

Stool form. In a randomized, double-blind, placebo-controlled trial, 44 healthy adults with a tendency toward loose stools took 5 g of PHGG a day for 12 weeks. Stool form moved toward normal compared with placebo, stool frequency did not change, and Bifidobacterium in stool increased.^[2] The trial was funded by a PHGG manufacturer, and three authors were its employees.

Constipation. In a single-blinded trial in 52 long-term care residents in Hong Kong with chronic constipation, average age 84, 5 g of PHGG in water daily for 4 weeks did not change bowel frequency or stool form compared with water alone. Use of as-needed laxatives was lower in the PHGG group in weeks 3 and 4.^[9] For constipation in general, a 2022 meta-analysis found the clearest effects for psyllium, at more than 10 g a day for at least four weeks.^[10]

Irritable bowel syndrome. An open-label trial randomized people with IBS to 5 g or 10 g of PHGG a day for 12 weeks. Symptom and quality-of-life scores improved from baseline in both groups, and the improvement faded after treatment stopped.^[11] There was no placebo group, so the trial cannot separate PHGG's effect from expectation or the natural course of symptoms.

Tube feeding. Diarrhea is common with enteral nutrition. In a double-blind trial in 100 hospital patients, a formula with 20 g of PHGG-containing soluble fiber per liter cut diarrhea compared with the same formula without fiber, but flatulence rose.^[12] A 2022 meta-analysis of 16 randomized trials found fiber-enriched formulas reduced diarrhea overall; in the 2 trials that used PHGG, the risk ratio was 0.47.^[13] These were hospitalized patients on liquid diets, a long way from a healthy adult with a drink mix.

The overall picture: PHGG is reasonably well studied for stool form and tube feeding, less so for constipation, and none of these trials enrolled people taking GLP-1 medications. How it compares with psyllium, inulin and other fibers is in fiber supplements compared.

Safety and interactions

No UL exists. The 2005 report concluded that high intakes of fiber from food do not cause significant harm in healthy people, and that for isolated fibers, occasional gastrointestinal symptoms occur but serious chronic adverse effects have not been observed; because fiber is bulky, excess intake tends to limit itself.^[4]

Gas is the effect to expect. The report cites a trial in which 16 older patients given 4 to 12 g a day of hydrolyzed guar gum had moderate to severe flatulence.^[4] In the long-term care trial, increased flatulence was reported by 8 people on PHGG and 3 on water, a difference that was not statistically significant.^[9] A psyllium label tells new users to start with one serving a day and build up gradually,^[14] and the same approach makes sense with PHGG. The report also notes that fiber causes gastrointestinal distress in some people with IBS.^[4]

Fluid. FDA requires over-the-counter fiber drug products containing guar gum and other swelling gums to warn about choking and to direct at least 8 ounces of fluid per dose.^[15] That rule covers drug products, not foods, but PHGG belongs in a full glass of liquid in any case. People who have difficulty swallowing should ask their clinician first.

Medicines. We found no interaction studies specific to PHGG. The psyllium label warns that bulk-forming fiber may affect how well other medicines work and says to take it at least 2 hours before or after a prescription medicine taken by mouth.^[14] PHGG is not a gel-former, but the same spacing is a cautious default. If you have had bowel surgery, a narrowing of the bowel, or have been told to follow a low-fiber diet, follow your clinician's advice instead.

If you take prescription medicine, ask your pharmacist or prescriber before adding a supplement.

In Replenish

Replenish is formulated with 3.5 g of PHGG per serving, listed on the Supplement Facts panel as partially hydrolyzed guar gum. It is the formula's prebiotic fiber, chosen because it dissolves clear in a drink, and it supports regularity.^† That is less than the 5 g of PHGG used in the trials above, and those trials tested PHGG on its own, not Replenish. It adds to the fiber in food rather than replacing it. See Replenish.