Guar Gum, Partially Hydrolyzed Guar Gum, and Human Gut Health: A Narrative Review

: Dietary fibers, and more specifically water-soluble fibers, beneficially affect human health. Guar gum and its enzymatic product, partially hydrolyzed guar gum (PHGG), are among the most studied dietary fibers in humans. Altogether, they can be described as "guar fiber". We performed a narrative review of the literature on guar fiber, namely guar gum and its partially hydrolyzed product, and their impact on human health, with a special focus on the gastrointestinal tract, gut microbiota, gut-brain axis, and liver steatosis. Accordingly, a literature search was conducted using the following keywords and combinations: guar fiber, guar gum, partially hydrolyzed guar gum, disorders of gut-brain interaction, gut-liver axis, and gut microbiota. Guar gum and its derivative, PHGG, show promising effects in gastrointestinal disorders, such as constipation and diarrhea. Interestingly, they can modulate the gut microbiota, with promising implications for the gut-brain axis and disorders of gut-brain interaction, such as irritable bowel syndrome. There are also interesting, albeit preliminary, results regarding their use in fatty liver disease. Thus, dietary fibers such as guar gum and, more importantly, its hydrolyzed product, show promising and better-documented effects on the health of the gastrointestinal tract and other organs and systems of the human body. However, the latter evidence still requires clinical confirmation of preclinical findings. Overall, the reviewed data vary in quality and maturity across different outcome domains.