Background Only 5% of adults consume the recommended level of dietary fiber. Fiber supplements appear to be a convenient and concentrated source of fiber, but most do not provide the health benefits associated with dietary fiber. Purpose This review will summarize the physical effects of isolated fibers in small and large intestines, which drive clinically meaningful health benefits. Data sources A comprehensive literature review was conducted (Scopus and PubMed) without limits to year of publication (latest date included: October 31, 2016). Conclusions The physical effects of fiber in the small intestine drive metabolic health effects (e.g., cholesterol lowering, improved glycemic control), and efficacy is a function of the viscosity of gel‐forming fibers (e.g., psyllium, β‐glucan). In the large intestine, fiber can provide a laxative effect if (a) it resists fermentation to remain intact throughout the large intestine, and (b) it increases percentage of water content to soften/bulk stool (e.g., wheat bran and psyllium). Implications for practice It is important for nurse practitioners to understand the underlying mechanisms that drive specific fiber‐related health benefits, and which fiber supplements have rigorous clinical data to support a recommendation. Clinical pearl For most fiber‐related beneficial effects, “Fiber needs to gel to keep your patients well.”

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