What Is It? Beta-glucans are a form of natural soluble dietary fiber found in foods, including grains (such as barley, oats, and corn bran) and mushrooms (such as maitake, reishi, and shiitake). Interestingly, one of the richest concentrated sources of beta-glucans is found in the cell walls of baker's yeast (Saccharomyces Cerevisae). Regardless of the source, however, all beta-glucans are carbohydrates formed by a string of glucose molecules. They are then absorbed into the body through the intestines. Beta-glucans are also available in various forms as dietary supplements. Manufacturers extract the key compounds from the soluble part of fibrous foods or from baker's yeast, and then remove all fats and proteins to refine and purify the extract. Packaged in pills and capsules, the beta-glucans are then sold to prevent or treat various ailments. Health Benefits Many uses have been proposed for beta-glucan dietary supplements--from promoting wound healing and lowering cholesterol levels to fighting cancer. Scientific research papers on beta-glucans abound. To date, however, clinical trials only support a few uses for this substance. Specifically, beta-glucans may help to: Reduce the risk of coronary heart disease by lowering blood cholesterol levels. Glucans that are soluble in water (such as a form called 1,6 glucans, which are extracted from whole oats) can help to reduce cholesterol levels when consumed as part of the healthy low-fat diet. The U.S. Food and Drug Administration (FDA) has ruled that companies such as Quaker Oats can make the claim that their products help to reduce the risk of heart disease--with certain stipulations. A serving must contain at least 0.75 grams of beta-glucan; the product must be used as part of a low-saturated-fat, low-cholesterol diet; and it has to contain no more than 3 grams of fat and no more than 1 gram of saturated fat. Many oatmeal and oat bran cereals and other products now meet the beta-glucan and other qualifications as heart disease preventers. Clinical trials have even shown that the higher the beta-glucan content of the oat cereal (hot or cold), the greater the cholesterol-lowering effect. However, there is still only limited evidence that beta-glucans taken in pill form can have this cholesterol-lowering effect. Enhance immune-system power. Beta-glucans appear to indirectly intensify the immune system's ability to fight off infection, apparently by activating certain white blood cells called macrophages. This has been shown in laboratory tests. Produced by the bone marrow, macrophages patrol the body, gobbling up such foreign invaders as bacteria and fungi. Macrophages must be stimulated (or "activated") in order to become functioning members of the immune system's A-Team. However, whether or not this activation by beta-glucans actually alters the outcome of any specific condition has yet to be proven. Protect against cancer and the development of tumors. Cancer researchers are conducting a variety of clinical trials to determine whether beta-glucans can boost the ability of the body's immune system to kill cancer cells. In one laboratory study, antibody medications were more effective in killing cancer cells when they were given in conjunction with beta-glucans. A number of follow-up clinical trials are under way.