OptiFiber Lean features Shimizu Propol^® A propolmannan—a highly pure, natural soluble fiber. Propol A is created from Amorphophallus konjac-derived glucomannan using proprietary processing techniques. This fiber has been studied for its viscosity and for its stability through the digestive tract; and studies support its health effects, such as on satiety, weight control, glucose and lipid metabolism, and bowel regularity.