Evidence Level
Psyllium husk has one of the strongest evidence bases of any fiber supplement. Wei et al. (2009) conducted a meta-analysis of 21 studies confirming significant LDL cholesterol reduction, which forms the basis of the FDA's approved health claim. Gibb et al. (2015) reviewed 35 RCTs and found consistent improvements in glycemic control in type 2 diabetes patients. The American College of Gastroenterology recommends psyllium as a first-line supplement for chronic constipation (grade A recommendation). More recently, the connection between soluble fiber fermentation and GLP-1 secretion has generated significant research interest, with Chambers et al. (2015) demonstrating that short-chain fatty acids from fiber fermentation directly stimulate GLP-1 release from colonic L-cells.