Beta glucan is a complex polysaccharide composed of glucose molecules extracted and purified from the cell wall of common baker's yeast, Saccharomyces cerevisiae. Beta Glucan is used to maintain or stimulate the effectiveness of the immune system. Animal and human cell culture studies have shown that beta glucan can stimulate several aspects of immune function, such as phagocytosis and interleukin production.
Beta-glucan is a fiber-type polysaccharide (complex sugar) derived from the cell wall of baker's yeast, oat and barley fiber, and many medicinal mushrooms, such as maitake. In their natural state, yeast and mushrooms contain a mixture of beta-1,3-glucan and beta-1,6-glucan. Oats and barley contain a mixture of beta-1,3-glucan and beta-1,4-glucan. In addition to purified beta-1,3-glucan from these sources, you may see products listed as beta-1,3/1,6-glucan in the case of yeast-derived products and as beta-1,3/1,4-glucan when derived from oats. Similar (if not identical) properties have been shown for beta-glucan-rich extracts and purified beta-glucan derived from oats, baker's yeast, and mushrooms. The two primary uses of beta-glucan are to enhance the immune system and to lower blood cholesterol levels.
Beta-glucan's anti-cancer abilities are thought to result from its immune effects. And its immune effects derive from its activation of macrophage cells. Macrophages are immune cells that trap and engulf foreign cells and particles, scavenge cellular debris, and destroy infectious agents such as viruses, parasites, bacteria, and fungi. Since beta-1,3-glucan produces its broad-scale immune effects by being a nonspecific immune stimulator, it can be directed at many health problems.
Yeast beta-D-glucan, usually referred to as yeast beta-glucan, consists of straight-chain and branched polymers. The straight-chain structures are (1/3)-beta-D-linked glucose polymers and (1/6)-beta-D-linked glucose polymers. The branched polymers consist of a (1/3)-beta-D-linked backbone containing varying degrees of (1-6)-beta branches. Yeast beta-glucan is sometimes designated as beta 1, 3/1, 6 glucan. Yeast beta-glucan appears to have immunomodulatory properties. It can bind to various cells of the non-specific immune system, such as macrophages and neutrophils. PGG-glucan or poly- [1, 6]-beta-D-glucopyranosyl- [1,3]-beta-D-glucopyranose is a genetically modified Saccharomyces cerevisiae beta-glucan. It is being evaluated in clinical studies as an immunomodulatory agent and a biological response modifier.
Oat beta-glucan is comprised of mixed-linkage polysaccharides. This means that the bonds between the D-glucose or D-glucopyranosyl units are either beta-1, 3 linkages or beta-1, 4 linkages. This type of beta-glucan is also referred to as a mixed-linkage (1→3), (1→4)-beta-D-glucan. Most of the oat bran beta-glucan molecules consist of cellotriose and cellotetraose blocks separated by (1→3)-linkages. There is, however, a smaller amount of sequences of (1→4)-linkages longer than the tetraose type. The (1→3)-linkages break up the uniform structure of the beta-D-glucan molecule and make it soluble and flexible. In comparison, the nondigestible polysaccharide cellulose is also a beta-glucan but is non-soluble. The reason that it is non-soluble is that cellulose consists only of (1→4)-beta-D-linkages. The percentages of beta-glucan in the various whole oat products are: oat bran, greater than 5.5%; rolled oats, about 4%; whole oat flour about 4%.