1. McRorie, Johnson W. Jr PhD, FACG, AGAF, FACN
  2. Gibb, Roger D. PhD
  3. Sloan, Kyle J. PharmD
  4. McKeown, Nicola M. PhD


Psyllium is a natural, predominantly soluble isolated fiber that forms a gel when hydrated. The psyllium gel is not fermented and transits the entire gastrointestinal tract intact. In the small intestine, the psyllium gel increases chyme viscosity, which slows the degradation and absorption of nutrients, which significantly improves fasting blood glucose and hemoglobin A1c levels in individuals with metabolic syndrome and type 2 diabetes mellitus (eg, -37 mg/dL). This delay in nutrient absorption prolongs satiety/delays hunger, leading to decreased energy intake and weight loss in overweight and obese patients. In the distal small intestine (terminal ileum), psyllium becomes more concentrated as water is absorbed, and the highly viscous gel interferes with the active reuptake of bile acids, which are captured in the gel and eliminated via stool. This decrease in the bile acid pool stimulates the liver to produce more bile. As cholesterol is a component of bile, the liver expresses low-density lipoprotein (LDL) cholesterol receptors to harvest LDL-cholesterol from the blood, thereby lowering both LDL-cholesterol (up to 24%) and total cholesterol (up to 20%) levels without affecting high-density lipoprotein cholesterol level. The cholesterol-lowering benefit of psyllium is also additive to the effects of statin drugs, with an effect equivalent to doubling the statin dose. In the large intestine, the nonfermented psyllium gel has a paradoxical "stool normalizing" effect: psyllium softens hard stool in constipation, firms loose/liquid stool in diarrhea, and normalizes stool form/reduces symptoms in irritable bowel syndrome. Psyllium is the only fiber recommended for treatment of constipation and irritable bowel syndrome by the American College of Gastroenterology. Taken together, psyllium is the only fiber supplement that provides 5 of the major health benefits identified by the Food and Drug Administration (cholesterol lowering, improved glycemic control, decreased energy intake/weight loss, decreased blood pressure secondary to weight loss, and laxation/regularity). Psyllium has also been shown clinically to be effective in disease states (eg, hypercholesterolemia, type 2 diabetes, obesity, chronic constipation, chronic diarrhea, hemorrhoids, ulcerative colitis, enteral nutrition-induced diarrhea, fecal incontinence, and irritable bowel syndrome). Taken together, the clinical data support the conclusion that "Fiber needs to gel to keep your patients well."