Supplement analysis backed by scientific evidence · PT

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Moderate evidenceWeight management

Guar Gum

A highly viscous soluble fibre from the guar bean. It has a real, replicated effect on blood sugar control, but the same meta-analysis that found it lowers HbA1c found no effect on body weight, so it is a poor choice if slimming is the goal.

Evidence last reviewed: August 2026

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What the science says

  • Improves glycaemic control Moderate evidence

    A GRADE-assessed systematic review and meta-analysis of 14 randomized trials found guar gum reduced HbA1c by about 0.47 units versus control, with fasting glucose reduced in the subgroup taking more than 15 g/day and in people with type 2 diabetes. The authors judged the evidence insufficient to base clinical guidelines on.

  • No effect on body weight Moderate evidence

    The same meta-analysis found no significant change in body mass, blood pressure or fasting glucose overall. Despite the weight-management positioning, viscous fibre appears to alter glucose handling more than it alters the scale.

  • Short-term satiety effects Limited evidence

    A comprehensive review of human intervention studies on extracted and isolated fibres found that viscous fibres including guar gum can reduce appetite ratings and short-term energy intake, but effects across studies were inconsistent and rarely persisted into sustained calorie reduction.

Dosage & safety

Studied doseTrials used roughly 5–20 g per day, with glycaemic benefit concentrated above 15 g/day, split across meals and taken with plenty of water. Partially hydrolysed guar gum (used in enteral nutrition and gut studies) is a different, non-viscous product with different effects.
SafetyBloating, gas, cramping and loose stools are common, especially when starting; increase the dose slowly. Guar gum absorbs water rapidly and has caused oesophageal and intestinal obstruction when taken with too little fluid, which is why old guar-based diet pills were withdrawn. It can slow the absorption of other medicines, so separate doses by two hours, and it may enhance the glucose-lowering effect of diabetes drugs. Avoid with swallowing difficulties or known intestinal strictures.

Scientific references

Where to buy

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