I hope you're doing well and enjoying summer. I also hope that you'll find the following article
about the health effects of glucans by Dr. Harriet Burge both interesting and useful.
With best wishes,
Health Effects of Glucans
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.
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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does not enhance the effectiveness of an energy-restricted diet in overweight women. British
Journal of Nutrition 103(8):1212-1222.
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.
4. Bonlokke JH, Stridh G, Sigsgaard T, Kaergaard SK, Lofstedt H, Andersson K, Bonefeld-Jorgensen
EC, Jayatissa MN, Bodin L, Juto JE, Molhave L. 2006. Upper-airway inflammation in relation to
dust spiked with aldehydes or glucan. Scandinavian Journal of Work Environment & Health 32(5):374-382.
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:
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and spatial variation of indoor and outdoor airborne fungal spores, pollen, and (1 -> 3)-beta-d-glucan.
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