Beta-1,3 Glucan

Overview

Glucans are polysaccharides that only contain glucose as structural components. Beta-1, 3 glucans are chains of polysaccharides (complex glucose molecules), with the six-sided 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 glucans are apparently those that contain 1,6 side-chains branching off from the longer beta-1, 3 glucan backbone. The formula for this type of compound is 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.

One of the most common sources of beta-1, 3 glucans is derived from the cell walls of baker’s yeast (Saccharomyces ceravisiae). However, beta-1, 3 glucans are also extracted from the bran of some grains such as oats and barley. The beta-1, 3 glucans from yeast are insoluble whereas those extracted from grains tend to be soluble. Other sources include some types of seaweed, (1) and various species of mushrooms such as Reishi, Shiitake, and Maitake. (2)

Beta-1, 3 glucans are being referred to as biological response modifiers because of their ability to activate the immune system. (3) However, it should be noted that the activity of beta-1, 3 glucans is different from agents that stimulate the immune system. Agents that stimulate the immune system can push the system to over-stimulation, and hence are contraindicated in individuals with autoimmune diseases. Beta-1, 3 glucans seem to make the immune system work better without becoming overactive. They accomplish this by activating the activity of macrophages, which are immune system cells whose function is to trap and destroy foreign substances in our bodies such as bacteria, viruses, fungi, and parasites. (4) Once activated, the macrophages can respond more quickly and efficiently to immune system challenges. In addition to enhancing the activity of macrophages, beta-1, 3 glucans also reportedly lower elevated levels of LDL cholesterol, aid in wound healing, help prevent infections, and help in the prevention and treatment of cancer.

Dosage Info

Dosage Range

From 3 mg to 3,000 mg daily.

Most Common Dosage

Variable, depending of body weight and whether it is being used for maintenance or an acute condition. For maintenance, doses from 75 to 250 mg daily are most common. It has been suggested that the minimal dose for a serious medical condition is 25 mg per kilogram of body weight.

Dosage Forms

Capsules, topical cream, and injectables.

Adult RDI

None established

Adult ODA

None established

Active Forms

Beta-1, 3 glucan with 1,6 glucan side chains, which are derived from yeasts, and some varieties of mushrooms, and the beta-1, 3 glucans with 1,4 side chains which occur primarily in grains such as oats and barley.

Absorption

For best results, beta-1, 3 glucans should be taken on an empty stomach. Enterocytes reportedly facilitate the transportation of beta-1, 3 glucans and similar compounds across the intestinal cell wall into the lymph where they begin to interact with macrophages to activate immune function. (5) Radio-labeled studies have verified that both small and large fragments of beta glucans are found in the serum, which indicates they are absorbed from the intestinal tract. (6)

Toxicities & Precautions

General

Beta-1, 3 glucan has been given a GRAS (Generally Recognized As Safe) rating by the FDA.

Allergy

Although side effects are rare, occasionally an allergic reaction is reported. (7) , (8)

Functions in the Body

Macrophage Activity

Beta-1, 3 glucans improve the body’s immune system defense against foreign invaders by enhancing the ability of macrophages to respond to and fight a wide range of toxic substances such as bacteria, viruses, fungi, and parasites. (9) , (10)

Immune System Activity

Beta-1, 3 glucans also increase the production of cytokines such as tumor necrosis factor (11) and certain subsets of T-lymphocytes. (12) Although this research has been done in animals, the results suggest that beta-1, 3 glucans enhance both non-specific host defense and cellular immune response.

Lowers Elevated Cholesterol Levels

Studies have reported that the beta-1, 3 glucans, which are soluble fiber components in grains such as oats and barley, are effective at lowering elevated total and LDL cholesterol levels. (13) , (14)

Non-immune receptors

It has recently been reported that part of beta-1,3 glucan’s activity in humans may be due to newly discovered glucan receptors on human dermal fibroblasts. Previously, beta-1,3 glucan activity was thought to be due to its reaction with receptors on immune system (leukocyte) cells. Now, it appears that some of beta-1,3 glucan’s functional activity may be due to its interaction with non-immune cells in the body. (15)

Clinical Applications

Cancer

Numerous studies report that beta-1, 3 glucan has anti-tumor and anti-cancer activity. (16) , (17) In one study, intralesional administration of beta-1, 3 glucans resulted in rapid tumor shrinkage. (18) In another study with mice, beta1, 3 glucan in conjunction with interferon gamma (INF-gamma) inhibited both the establishment of tumors and liver metastasis. (19) In some studies, beta-1, 3 glucans potentiate 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. (20) In human patients with advanced gastric or colorectal cancer, the administration of beta-1, 3 glucans derived from shiitake mushrooms, in conjunction with chemotherapy (mitomycin C + 5-Fluorouracil) resulted in prolonged survival times compared to a control group receiving identical chemotherapy. (21)

Infections

41 patients with multiple trauma (but no infections) were admitted to a double-blind trial to receive beta-1, 3 glucan or a placebo. 11 of 20 controls contracted pneumonia vs only 2 of 21 treated with beta-1, 3 glucan. Sepsis developed in 35% of controls vs 9.5% of those treated with glucan; deaths due to infection and general mortality in controls was 30% and 42.1% compared to 4.8% and 23.5% in the beta-1, 3 glucan-treated group. (22)

Wound Healing

Macrophage activity is known to play a key role in wound healing from surgery or trauma. In both animal and human studies, therapy with beta glucan has provided improvements such as fewer infections, reduced mortality, and stronger tensile strength of scar tissue. (23) , (24)

Elevated Cholesterol

Beta-glucans appear to be the major cholesterol lowering agents in oat bran fiber. This dietary fiber, 0.75 g/serving given four servings a day, has been approved by The US Food and Drug Administration (FDA) to reduce cardiovascular disease risk. (25) Studies reveal that soluble beta-1, 3 glucans in oat bran can lower total cholesterol and LDL cholesterol levels in patients with hypercholesterolemia. (26) , (27) Similar cholesterol lowering effects are reported in studies where barley is the source of beta-1, 3 glucans. (28)

A randomized crossover study fed a high-fiber (beta-glucan or psyllium) and a control low-fat, low-cholesterol diet for 1 month each to 68 hyperlipidemic adults. Based on various reductions in cholesterol measures and ratios, a risk reduction of 4.2 +/- 1.4% (P = 0.003), as calculated by the Framingham cardiovascular disease risk equation, was noted for cardiovascular disease. This supports the FDA's approval of a health claim for a dietary fiber intake of 4 servings per day. (29)

Septic Shock

Toxins from either external or internal (infections) sources cause leukocytes to release pro-inflammatory cytokines that can produce a series of biochemical events that ends in septic shock. Administration of soluble beta-1, 3/1/6 glucans reduces the production of pro-inflammatory cytokines, most notably Tumor Necrosis Factor-alpha (TNF-alpha), which reduces mortality. (30)

Symptoms and Causes of Deficiency

Beta-1, 3 glucans do not occur naturally in humans, hence no deficiency condition exists.

Dietary Sources

Although beta-1, 3 glucans occur in bakers yeast, grains such as oats and barley, and several types of mushrooms, they are not readily useable in their natural state. The indigestible cell walls of these substances must be processed in order to free up the beta-1, 3 glucans and make them available for useful purposes.

References

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  20. View Abstract: Thompson IM, Spence CR, Lamm DL, et al. Immunochemotherapy of bladder carcinoma with glucan and cyclophosphamide. Am J Med Sci. Nov1987;294(5):294-300.
  21. View Abstract: Wakui A, Kasai M, Konno K, et al. Randomized study of lentinan on patients with advanced gastric and colorectal cancer. Tohoku Lentinan Study Group. Gan To Kagaku Ryoho. Apr1986;13(4 Pt 1):1050-9.
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  30. View Abstract: Soltys J, Quinn MT. Modulation of endotoxin- and enterotoxin-induced cytokine release by in vivo treatment with beta- (1,6)-branched beta- (1,3)-glucan. Infect Immun. Jan1999;67(1):244-52.