Citrucel Sugar Free Fiber Therapy, Orange, 16.9 Ounce Fiber for irregularity that wont cause excess gas. (Based on laboratory testing. Individual results may vary.) Clinically proven** effective to relieve occasional constipation. Citrucel contains Methylcellulose Fiber, which is a non-toxic, non-allergenic, and non-irritant fiber. Sugar Free has a great-tasting orange flavor and is a smart choice for sugar-restricted diets. Contains Methylcellulose Fiber, a fiber derived from cellulose. Available in 16.9-ounce, 32-ounce, 42-ounce powders. Citrucel is recommended by physicians (among therapeutic fiber laxatives). **Snape W. The Effect of Methylcellulose on Symptoms of Constipation. Clinical Therapeutics .1989; Sep-Oct;11(5):572-9.