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Health Effects of Glucans

Types of Glucans and Positive and Negative Health Effects

By Dr. Harriet Burge, EMLab P&K Chief Aerobiologist and Director of Scientific Advisory Board

The Nature of Glucans
Glucans are polycaccharides composed of D-glucose monomers linked by glycosidic bonds. There are many different forms, each with different biological activities. The term "glucan" is therefore too general to be useful in this discussion.

Alpha vs. Beta Glucans
Alpha (α) and beta (β) glucans are differentiated by stereochemistry. Alpha glycosidic bonds are formed in an axial position while beta glycosidic bonds are formed in an equatorial position. Numbering of both alpha and beta glucans relate to the number of the carbon atoms on which the glycosidic bond is formed. Thus, in a beta-1,3 glucan, the glycosidic bonds are formed at the first and third carbons in the glucose ring.

Common Alpha Glucans

  • Dextran, an α-1,6-glucan, is synthesized by lactic acid bacteria. It is abundant in dental plaque and is said to be responsible for the positive health effects of drinking kefir.
  • Glycogen, α-1,4- and α-1,6-glucan, is commonly referred to as "animal starch" and is the long term storage carbohydrate in animals and fungi.
  • Pullulan, α-1,4- and α-1,6-glucan, is produced during the digestion of starch by the common fungus, Aureobasidium pullulans, and is used in the manufacture of thin edible films used as breath fresheners.
  • Starch, α-1,4- and α-1,6-glucan, is the storage carbohydrate in all green plants. It is present in virtually all of the grains, fruits, and vegetables that we eat.

Common Beta Glucans

  • Cellulose, a β-1,4-glucan, forms the structure of the cell wall of plants, a few "fungi" (fungal-like organisms, not true fungi), and is secreted by some bacteria to form biofilms. It is a part of the diet of omnivores (including humans) and herbivores. Omnivores digest only a fraction of ingested cellulose; the rest is considered "roughage." Herbivores and termites can digest cellulose with the help of microorganisms that live in their gut.
  • Curdlan, a β-1,3-glucan, is produced by the bacterium Agrobacterium biobar, and is used industrially to form elastic gels.
  • Laminarin, a β-1,3- and β-1,6-glucan, is the storage carbohydrate of the brown algae.
  • Chrysolaminarin, a β-1,3-glucan, is the storage carbohydrate of the golden brown algae (phytoplankton).
  • Lentinan, a purified β-1,6:β-1,3-glucan, is derived from the mushroom Lentinula edodes (the shiitake mushroom). It is administered intravenously as an anticancer agent.
  • Lichenin, a β-1,3- and β-1,4-glucan, is found in some lichens (particularly one called Icelandic moss).
  • Pleuran, a β-1,3- and β-1,6-glucan, is isolated from the edible mushroom Pleurotus ostreatus. Like lentinen, it has anti-cancer properties and is an immunostimulant.
  • Zymosan, a β-1,3-glucan, is isolated from yeast cell walls. It is an inflammatory agent that stimulates macrophage activation.

Glucan Exposure
Glucans are commonly ingested, and as mentioned above, are injected in some medical procedures. Glucans are also commonly inhaled, since all airborne fungal spores have cell walls containing primarily beta glucan. Glucan-containing airborne particles tend to be in the large particle fraction of indoor (and probably also outdoor) aerosols (Chen and Hildeman 2009; Menetrez et al., 2009). The vast majority of fungal glucan exposure occurs outdoors. Crawford et al. (2009) measured 1,3 β d glucan indoors (geometric mean 1.0 ng/m3, range 0.81-1.2) and outdoors (geometric mean 7.34 ng/m3, range 6.1-8.9). In a similar study, Lee et al. (2006) found geometric mean concentrations indoors of 0.92 ng/m3 and outdoors of 6.44 ng/m3. The geometric mean indoor/outdoor ratio was 0.14.

Positive Health Effects of Glucans
Exposure to glucans is natural and occurs throughout life. They have been shown to be immunostimulants, and may contribute to the early development of the immune system in newborns. Glucans have been widely studied as anti-cancer agents (Ma et al., 2010). In the laboratory, positive effects on lung cancer (Zhong et al., 2009), leukemia (Gao et al., 2007; McCormack et al., 2010), melanoma (Kamiryo et al., 2005), prostate cancer (Fullerton et al., 2000), and many others have been found. Glucan oral supplements have also been studied in relation to their effect on glucose metabolism and diabetes (Nazare et al., 2009). They are also advertised as an aid to weight loss, however Beck et al. (2010), found no enhancement of weight loss by oak glucans. Talbott and Talbott (2010) found positive effects of beta-glucan supplements on respiratory disease (fewer symptoms), vigor, tension, fatigue and confusion.

Negative Health Effects of Glucans
There is considerable controversy about the negative health effects of exposure to beta-glucans. Some evidence has been found that inhalation of glucans can be irritating. Inhalation challenges have resulted in stimulation of inflammatory cells (Beijer et al., 2002), however this group used glucan from the polypore fungus, Grifola frondosa (not a common exposure source), and the concentrations used were quite high compared to reported concentrations in air (28.1 ng/m3, range 17.1-44.9). Bodin et al. (2009) also used chamber exposures to study irritant effects of dust alone, dust with added glucan, and dust with added aldehydes. Only those with nasal hyperreactivity from some previous cause reacted to the exposures. In another chamber study (Bonlokke et al., 2006), the same group measured small changes in nasal volume and other parameters with all exposures. They considered glucan to have a stimulatory effect when other particles are present. They and others (e.g., Young et al., 2003), noted that particulate glucan has a stronger inflammatory effect than soluble glucan. In the laboratory, Holck et al. (2007) used several glucans in lymphocyte culture and found that the glucans increased histamine release only when combined with antigen (dust mite).

On the other hand, several research groups report no health related effects associated with inhalation of indoor glucans (Codispoti et al., 2010; Blanc et al., 2005; Schramm-Bijkerk et al., 2005). This lack of effect was confirmed by Stuurman et al. (2008) in bakers with much higher exposure to glucans than are found in residential environments.

Overall then, while there is laboratory evidence for a role of β glucans in inflammation, the effects appear to be limited to relatively high exposures and to occur in those already experiencing hyperreactivity from other causes.

Measurement of Glucans
Glucans have been collected both from dust and from air, and measurement of glucans is used for the detection of invasive fungal infections (Patterson 2010). A Limulus assay, that is similar to the endotoxin assay, is the most common method used for sample analysis. The molecular basis of these assays is described by Muta (2006). Both rely on the effects of these chemicals on horseshoe crab leucocytes. More recently, sensitive immunoassays have been developed that use monoclonal antibodies. These assays have enabled the measurement of low level glucans in air (Noss et al., 2010; Sander et al., 2008).

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2. Beijer L, Thorn J, Rylander R. 2002. Effects after inhalation of (1 -> 3)-beta-D-glucan and relation to mould exposure in the home. Mediators of Inflammation 11:3149-3153.

3. Blanc PD, Eisner MD, Katz PP, Yen H, Archea C, Earnest G, Janson S, Masharani UB, Quinlan PJ, Hammond SK, Thorne PS, Balmes JR, Trupin L, Yelin EH. 2005. Impact of the Home Indoor Environment on Adult Asthma and Rhinitis. Journal of Occupational & Environmental Medicine 47(4):362-372.

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5. Bodin L, Andersson K, Bonlokke JH, Molhave L, Kjaergaard SK, Stridh G, Juto JE, Sigsgaard T. 2009. Nasal hyperresponders and atopic subjects report different symptom intensity to air quality: a climate chamber study. Indoor Air 19(3):218-225.

6. Chen Q, Hildemann LM. 2009. Size-Resolved Concentrations of Particulate Matter and Bioaerosols Inside versus Outside of Homes. Aerosol Science and Technology 43(7):699-713.

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9. Fullerton SA, Samadi AA, Tortorelis DG, et al. 2000. Induction of apoptosis in human prostatic cancer cells with beta-glucan (Maitake mushroom polysaccharide). Molecular Urology 4(1):7-13.

10. Gao L, Sun Y, Chen C, et al. 2007. Primary mechanism of apoptosis induction in a leukemia cell line by fraction FA-2-b-ss prepared from the mushroom Agaricus blazei Murill. Brazilian Journal of Medical and Biological Research 40:1545-1555.

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12. Kamiryo, Y, Yajima, T, Saito, K, et al. 2005. Soluble branched (1,4)-beta-D-glucans from Acetobacter species enhance antitumor activities against MHC class I-negative and -positive malignant melanoma through augmented NK activity and cytotoxic T-cell response. International Journal of Cancer 115(5):769-776.

13. Lee T, Grinshpun SA, Kim KY, Iossifova Y, Adhikari A, Reponen T. 2006 Relationship between indoor and outdoor airborne fungal spores, pollen, and (1 -> 3)-beta-D-glucan in homes without visible mold growth. Aerobiologia 22(3):227-236.

14. Ma ZC, Wang JG, Zhang LN, Zhang YF, Ding K. 2010. Evaluation of water soluble beta-D-glucan from Auricularia auricular-judae as potential anti-tumor agent. Carbohydrate Polymers 80(3): 977-983.

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17. Muta T. 2006. Molecular basis for invertebrate innate immune recognition of (1 -> 3)-beta-D-glucan as a pathogen-associated molecular pattern. Current Pharmaceutical Design 12(32):4155-4161.

18. Noss I, Wouters IM, Bezemer G, Metwali N, Sander I, Raulf-Heimsoth M, Heederik DJJ, Thorne PS, Doekes G. 2010. Beta-(1,3)-Glucan Exposure Assessment by Passive Airborne Dust Sampling and New Sensitive Immunoassays. Applied and Environmental Microbiology 76(4):1158-1167.

19. Patterson T. 2010. Clinical Utility of Biomarkers in Fungal Infection. International Journal of Infectious Diseases 14: E317-E318.

20. Sander I, Fleischer C, Borowitzki G, Bruning T, Raulf-Heimsoth M. 2008. Development of a two-site enzyme immunoassay based on monoclonal antibodies to measure airborne exposure to (1 -> 3)-beta-D-glucan. Journal of Immunological Methods 337(1):55-62.

21. Schram-Bijkerk D, Doekes G, Douwes J, Boeve M, Riedler J, Ublagger E, Mutius E, Benz MR, Pershagen G, Hage M, Scheynius A, Braun-Fahrlander C, Waser M, Brunekreef B. 2005. Bacterial and fungal agents in house dust and wheeze in children: the PARSIFAL study. Clinical and Experimental Allergy 35(10)1272:1278.

22. Sonck E, Stuyven E, Goddeeris B, Cox E. 2010. The effect of beta-glucans on porcine leukocytes. Vet Immunol Immunopathol 135(3-4):199-207.

23. Stuurman B, Meijster T, Heederik D, Doekes G. 2008. Inhalable beta(1 -> 3) glucans as a non-allergenic exposure factor in Dutch bakeries. Occupational and Environmental Medicine 65(1):68-70.

24. Talbott S, Talbott J . 2010. Beta 1,3/1,6 glucan decreases upper respiratory tract infection symptoms and improves psychological well-being in moderate to highly-stressed subjects. Agro Food Industry Hi Tech 21(1): 21-24.

25. Young SH, Robinson VA, Barger M, Whitmer M, Porter DW, Frazer DG, Castranova V. 2003. Exposure to particulate 1 -> 3-beta-glucans induces greater pulmonary toxicity than soluble 1 -> 3-beta-glucans in rats. Journal of Toxicology and Environmental Health-Part A 66(1):25-38.

26. Zhong WJ, Hansen R, Li B, Cai YH, Salvador C, Moore GD, Yan J. 2009. Effect of Yeast-derived beta-glucan in Conjunction With Bevacizumab for the Treatment of Human Lung Adenocarcinoma in Subcutaneous and Orthotopic Xenograft Models. Journal of Immunotherapy. 32(7):703-712.


This article was originally published on June 2010.