Beta-glucans are sugars that are found in the cell walls of bacteria, fungi, yeasts, algae, lichens, and plants. They are sometimes used as medicine. Beta-glucans are taken by mouth for high cholesterol, diabetes, cancer, HIV/AIDS, high blood pressure, and canker sores. Beta-glucans are also taken by mouth to boost the immune system in people whose body defenses have been weakened by conditions. It is one form of soluble dietary fiber that’s strongly linked to improving cholesterol levels and boosting heart health.