Beta Glucans are polysaccharides that only contain glucose as structural components. Beta 1,3-D glucans are chains of D-glucose molecules, with the six-sided D-glucose rings connected at the 1 and 3 positions. Smaller side chains branch off the 1,3 polysaccharide “backbone.” The most active form of Beta 1,3-D glucans are apparently those that contain 1,6 side-chains branching off from the longer beta-1,3 glucan backbone. These are referred to as beta-1,3/1,6 glucan. Some researchers have suggested that it is the frequency, location, and length of the side-chains rather than the backbone of beta glucans that determine their immune system activity. Another variable is the fact that some of these compounds exist as single strand chains, while the backbones of other beta-1,3 glucans exist as double or triple stranded helix chains. In some cases, proteins linked to the beta-1,3 glucan backbone may also be involved in providing therapeutic activity. Although these compounds have exciting potential for enhancement of the immune system, it must be emphasized that this research is in its infancy, and there are differing opinions on which molecular weight, shape, structure, and source of beta-1,3 glucans provide the greatest therapeutic benefit.
Beta Glucan has been used as an immunoadjuvant therapy for cancer since 1980, primarily in Japan. Numerous studies report that beta-1, 3 glucan has anti-tumor and anti-cancer activity. In one study, intralesional administration of beta-1,3 glucans resulted in rapid tumor shrinkage. In another study with mice, beta 1,3 glucan in conjunction with interferon gamma inhibited both the establishment of tumors and liver metastasis. In some studies, beta-1,3 glucans enhanced the effects of chemotherapy. In studies on bladder cancer with mice, administration of cyclophosphamide, in conjunction with beta-1,3 glucans derived from yeast resulted in reduced mortality. In human patients with advanced gastric or colorectal cancer, the administration of beta-1,3 glucans derived from shiitake mushrooms, in conjunction with chemotherapy resulted in prolonged survival times compared to a control group receiving identical chemotherapy.
Beta Glucan is a well-known biological response modifier (BRM) isolated from the yeast cell wall polysaccharides and is made up entirely of glucose β(1,3)-linked together in linear chains with variable frequency of β(1,6)-linked side chains. Specific hematopoietic activity was first demonstrated with β-glucan in the mid-1980s in an analogous manner as granulocyte monocyte–colony stimulating factor (GM-CSF). Research was carried out initially with particulate β-glucan and later with soluble β-glucans, all of which were administered intravenously to mice. Mice exposed to 500-900 cGy (500-900 mrads) of gamma radiation exhibited a significantly enhanced recovery of blood leukocyte, platelet and red blood cell counts when given i.v. β-glucan. Other reports showed that β-glucan could reverse the myelo-suppression produced with chemotherapeutic drugs such as fluorouracil, carboplatinum or cyclophosphamide. Moreover, the anti-infective activity of beta glucan combined with its hematopoiesis-stimulating activity resulted in enhanced survival of mice receiving a lethal dose of 900-1200 cGy of radiation.