Bulking agents, such as dietary fiber (e.g., psyllium husk, methylcellulose), are scientifically validated for supporting rectal and overall lower gastrointestinal health. Their primary mechanism involves absorbing water and increasing the bulk and moisture content of stool, making it softer and easier to pass. This action helps normalize bowel movements and is especially beneficial for patients with constipation or irregular bowel habits. Numerous clinical trials and meta-analyses have demonstrated that bulking agents significantly improve stool frequency and consistency, reduce straining, and decrease the risk of complications such as hemorrhoids and anal fissures, which directly affect the rectum.

Guidelines from gastroenterological societies (such as the American College of Gastroenterology) recommend bulking agents as a first-line therapy for chronic constipation and as part of the management of conditions like irritable bowel syndrome with constipation (IBS-C). Bulking agents are also used in the prevention and treatment of diverticulosis and to facilitate easier defecation in patients recovering from anorectal surgery.

Overall, the evidence supporting the use of bulking agents for rectal health is robust, with multiple high-quality studies confirming their efficacy and safety profile. Their role is well-established in both clinical practice and dietary recommendations for promoting rectal and bowel health.