Beta-Glucan Boosts Immunity

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From The January 2001 Issue of Nutrition Science News

http://www.newhope.com/nutritionsciencenews/NSN_backs/Jan_01/betagluc

an.cfm

 

Beta-Glucan Boosts Immunity

by Carmia Borek, Ph.D

 

Beta-glucan is a natural, branched polysaccharide (a molecule made

up of many sugar units) hailed as having powerful and immune-

boosting anticancer properties.

 

Beta-glucan, with 1,3- and 1,6-glucose links, is isolated from a

variety of fungi such as shiitake (Lentinus edodes) and maitake

(Grifola frondosa) mushrooms,1 from yeast cell walls including

brewers' and bakers' yeasts (of the genus Saccharomyces),2,3 and

from oat and barley bran.4 The 1,3 refers to the sites at which

glucose molecules are connected to form the glucan backbone. The 1,6

refers to the bonding sites between a glucose molecule on the

backbone and on the side chains.

 

Beta-glucan enhances immunity through a variety of mechanisms, many

similar to those of echinacea (Echinacea spp.) or astragalus root

(Astragalus membranacseus). For example, beta-glucan binds to

macrophages and other phagocytic white blood cells at certain

receptors and activates their anti-infection and anti-tumor activity

by stimulating the production of free radicals. 5 This stimulation

signals the phagocytic immune cells to engulf and destroy foreign

bodies, be they bacteria, viruses or tumor cells.6

 

Researchers at Alpha-Beta Technology in Worcester, Mass., examined

the effects of beta-glucan on human blood. When the two were

incubated together, beta-glucan enhanced the growth of myeloid and

megakaryocyte progenitor cells, which develop into immune cells, and

triggered a burst of free radicals in white blood cells, enhancing

the cells' antibacterial activity. The white blood cells' bacterial

killing capacity was proportional to the glucan dose.

 

An important use of beta-glucan's immune-enhancing capability is

reducing the rate of postoperative infections that frequently

complicate high-risk surgical procedures. In three separate

multicenter, randomized, double-blind, placebo-controlled clinical

trials, researchers tested the effects of beta-glucan on patients

undergoing high-risk major abdominal and thoracic surgery or high-

risk gastrointestinal surgery. Results showed that patients who

received beta-glucan (doses ranged from 0.1 mg/kg to 2.0 mg/kg) had

significantly fewer postoperative infectious complications compared

with placebo.7-9 The investigators concluded that beta-glucan was

safe and well tolerated and could potentially decrease life-

threateningpostoperative infections.

 

Beta-Glucan vs. Cancer

In response to the specific appearance of tumor cells, beta-glucan

also stimulates the production of small protein compounds called

cytokines within the phagocytic cells. This cytokine stimulation

increases the capacity of macrophages to stop tumor cell growth

(cytostatic action) and kill the tumor in its entirety (cytolytic

action).10

 

Beta-glucan's ability to activate macrophages and T-cells led

researchers to evaluate it as an anti-cancer treatment or adjuvant

to chemotherapy. One animal study tested the effects of beta-glucan

injected into mice previously given aggressive tumor cells that

spread to their livers. A separate group was injected with only

tumor cells. Researchers found the beta-glucan-treated animals had

decreased liver metastases compared with control animals. The

control animals died within 42 days, but the beta-glucan-treated

mice had a 28 percent survival rate. These results indicate that

beta-glucan helped mount an immune attack on the cancer cells and

reduced their ability to metastasize.11

 

Although most domestic research has been done using animals, some

human studies have been conducted. For example, in 1975, the Journal

of the National Cancer Institute published the results of a human

study reviewing the anti-cancer effects of beta-glucan on nine

cancer patients. The patients, who had skin, breast, or lung cancer,

had beta-glucan injected into their tumors. In all cases, beta-

glucan reduced the size of the tumor within five days, a result

associated with an infiltration of immune cells into the cancerous

area and their destruction of the cancer cells.12

 

In Japan, clinical studies have also been conducted (though not

placebo-controlled and double-blind) with lentinan (a beta-1,3-1,6-

glucan derived from the shiitake mushroom), which is approved for

clinical use in Japan. A number of studies in Japan have also shown

that treatment of advanced-cancer patients with lentinan, by

intravenous injection, results in increased number and activity of

immune killer cells13 and in prolonged survival,14 sometimes five or

more years.

 

Beta-Glucan the Supplement

Beta-glucan is generally recognized as safe (GRAS) by the U.S. Food

and Drug Administration (FDA). It is not a government-regulated

substance, and, as of yet, there are no data from placebo-

controlled, double-blind human trials to recommend daily doses to

boost immunity in healthy or sick people.

 

Beta-glucan manufacturers and distributors recommend doses ranging

from 30 to 500 mg/day, and twice that during illness. Beta-glucan is

available in capsule, liquid or tablet form. Whole mushroom

extracts, such as maitake, are also available with a defined beta-

glucan content. With no concrete information on effective beta-

glucan doses, advise customers to consult their health care provider

before taking the product. Although evidence is far from conclusive,

beta-glucan may be a great way to boost immunity as well as

potentially fight cancer and other chronic diseases.

 

Carmia Borek, Ph.D. is a research professor at Tufts University

School of Medicine in Boston.

 

References

 

1. Mizuno T, et al. Antitumoractive substances from mushrooms. Food

Rev Int 1995;11:23-6.

 

2. Tokunaka K, et al. Immunological and imunotoxicological

activities of a water soluble 1-3 beta D glucan, CSBG, from a

Candida spp. Int J Immunopharmacol 2000; 22:383-94.

 

3. Bacon J, et al. The glucan component of the cell wall of baker's

yeast (Saccharomyces cerevisiae) considered in relation to its

ultrastructure. Biochem J 1969;114:557-67.

 

4. Baur SK, Geisler G. Variability of the beta-glucan content in oat

caryopsis of 132 cultivated oat genotypes and 39 wild oat genotypes.

J Agr Crop Sci 1996;176:151-7.

 

5. Adachi Y, et al. The effect enhancement of cytokine production by

macrophages stimulated with 1,3 beta D glucan, grifolan, isolated

from Grifola frondosa. Biol Pharm Bull 1994;17:1554-60.

 

6. Ohno N, et al. Effect of beta-glucan on the nitric oxide

synthesis of peritoneal macrophage (sic) in mice. Biol Pharm Bull

1996;19:608-12.

 

7. Babineau TJ, et al. Randomized phase I/II trial of

a macrophage-specific immunomodulator (PGG-glucan) in high-risk

surgical patients. Ann Surg 1994;220:601-9.

 

8. Babineau TJ, et al. A phase II multicenter double-blind

randomized placebo-controlled study of three dosages of an

immunomodulator (PGG-glucan) in high-risk surgical patients. Arch

Surg 1994;129:1204-10.

 

9. Dellinger EP, et al. Effect of PGG glucan on the rate of serious

postoperative infection or death observed after high-risk

gastrointestinal operations. Betafectin Gastrointestinal Study. Arch

Surg 1999; 13:977-83.

 

10. Seljelid R, et al. A soluble beta 1,3 glucan derivative

potentiates the cytostatic and cytolytic capacity of mouse

peritoneal macrophages in vitro. Immunopharmacology 1984;7:69-73.

 

11. Williams DL, et al. Therapeutic efficacy of glucan in a murine

model of hepatic metastatic disease. Hepatology 1985;5:198-206.

 

12. Mansell PW, et al. Macrophage mediated destruction of human

malignant cells in vivo. J Natl Cancer Inst 1975;54:571-80.

 

13. Matsuoka H, et al. Lentinan potentiates immunity and prolongs

the survival time of some patients. Anticancer Res 1997;17:2251-55.

 

14. Nakano H, et al. A multi-institutional prospective study of

lentinan in advanced gastric cancer patients with unresectable and

recurrent disease: effects on prolongation of survival and

improvement of quality of life. Kanagawa Research Group.

Hepatogastroenterology 1999;46:2662-8.