β-glucans are soluble fibres found in the cell walls of plants and bacteria, including mushrooms, seaweeds, oats and other grains. The shape, structure and molecular weight of β- glucans is different in mushroom than it is in oats and cereals, and these structural differences determine what they do in the body. Cereal β-glucans have been shown to help balance blood sugar. Because of their shape, cereal β-glucans resist digestion and absorption and, as a result, may help to  improve the gut microbiome and lower serum cholesterol.[1]            

Although the β-glucans in mushrooms also support the health of the gut microbiome, they are more well known as powerful adaptogens that help your body regain and maintain homeostasis or balance. Mushroom β-glucans are also potent immune system modulators. This means that they can prime the immune system for attack when necessary, and thereby increase your ability to resist invading germs and viruses. In other words, they optimize immune function rather than directly impacting a pathogen.        

Optimize Immunity

Mushroom β-glucans boost immunity because their shape allows them to bind to different receptors on the surface of immune system cells, including phagocytic cells (that engulf invaders); cytotoxic (sniper) immune cells; neutrophils (that patrol, trap and kill invaders along with a plethora of other tasks); and natural killer (NK) cells.[2]  NK cells are part of the innate immune system and are best known for killing cells that have been infected with a virus, as well as for detecting and controlling early signs of cancer.  β-glucans connect with these cells in the mucosal immune system of the digestive tract.

Fruiting body factor

Studies have shown that some β-glucans in a several mushroom species are more concentrated in the fruiting body[3], which is the part of the mushroom you see above-ground and enjoy raw or sauteed in your supper. It’s important to remember that researchers often use the fruiting body when investigating the health benefits of mushrooms – and how they do what they do for you.¹

And not all mushrooms do the same things

In fact, the content and proportions of β-glucans in fungi is mainly determined by genetics and differs between species.¹ For example, β-glucans in Ganoderma lucidum (reishi) have been shown to be potent stimulators of macrophage cells. These cells are part of the innate immune system and they are critical for detecting and eliminating diseased and damaged cells. Macrophages trigger antimicrobial processes or engulf the pathogen (phagocytosis).

On the other hand, the mushroom Trametes versicolor (turkey tail) is a source of the polysaccharopeptide krestin (PSK), which consists of β-glucan and peptide. PSK stimulates the launch of T-cells, which are the bridge between innate and adaptive immunity as they help kick-start the adaptive immune system. PSK also activates white blood cells that protect your from intra- and extracellular bacteria and viruses.[4] Finally, PSK stimulates the activity of cytokines.[5] The word “cytokine” is derived from the Greek cyto (cell) and kinos (movement). These signaling molecules allow cells to communicate in immune responses and encourage the movement of cells towards sites of infection, inflammation, and injury.

Cholesterol care

Mushroom β-glucans also can play a role in reducing cholesterol levels, but they operate differently than the cereal version. While researchers still haven’t figured out the exact process, it’s clear that, because they are not fully digestible by humans, mushroom β- glucans are prebiotics. This means that they become a food source for the good bacteria in your gut. Once mushroom β- glucans are fermented by the intestinal microflora, short-chain fatty acids (SCFA) are produced. SCFA are not only able to reduce the amount of cholesterol your body produces, but they also can increase cholesterol break-down.[6]

Through a different pathway, mushroom β-glucans reduce cholesterol by forming a gel on the surface of the bowel and blocking intestinal reabsorption of bile salts. The β-glucans also trigger bile salt production in the liver. Cholesterol is a building block of bile salts: The additional bile salt production uses up cholesterol, meaning less is available to circulate in the blood. Dietary fibres also trap lipids and cholesterol, decrease their absorption, and help to shuttle them out of the body as waste.³ 

Safety matters 

The study of β-glucans is rather new and we can expect to learn more as researchers focus on various mushroom species. So far, though, it’s clear that mushroom β-glucans may play a role in supporting healthy cholesterol levels and immune system function.

Unlike other immunomodulators, however, mushroom β-glucans show low-to-negligible toxicity in studies. Stay tuned for new findings concerning these powerhouse mushroom nutrients can optimize immune system function against infections and disease![7] 

REFERENCES

[1] Van Steenwijk, H. P., Bast, A., & De Boer, A. (2021). Immunomodulating Effects of Fungal Beta-Glucans: From Traditional Use to Medicine. Nutrients, 13(4), 1333–. https://doi.org/10.3390/nu13041333

[2] Camilli, G., Tabouret, G., & Quintin, J. (2018). The Complexity of Fungal β-Glucan in Health and Disease: Effects on the Mononuclear Phagocyte System. Frontiers in Immunology, 9, 673–673. https://doi.org/10.3389/fimmu.2018.00673

[3] Nitschke, Modick, H., Busch, E., von Rekowski, R. W., Altenbach, H.-J., & Mölleken, H. (2011). A new colorimetric method to quantify β-1,3-1,6-glucans in comparison with total β-1,3-glucans in edible mushrooms. Food Chemistry, 127(2), 791–796. https://doi.org/10.1016/j.foodchem.2010.12.149

[4] Moradali, M.-F., Mostafavi, H., Ghods, S., & Hedjaroude, G.-A. (2007). Immunomodulating and anticancer agents in the realm of macromycetes fungi (macrofungi). International Immunopharmacology, 7(6), 701–724. https://doi.org/10.1016/j.intimp.2007.01.008

[5] Ren, L., Perera, C., & Hemar, Y. (2012). Antitumor activity of mushroom polysaccharides: a review. Food & Function, 3(11), 1118–1130. https://doi.org/10.1039/c2fo10279j

[6] Cerletti, C., Esposito, S., & Iacoviello, L. (2021). Edible Mushrooms and Beta-Glucans: Impact on Human Health. Nutrients, 13(7), 2195–. https://doi.org/10.3390/nu13072195

[7] Novak, M. & Vetvicka, V. (2008) β-Glucans, History, and the Present: Immunomodulatory Aspects and Mechanisms of Action, Journal of Immunotoxicology, 5:1, 47-57, DOI: 10.1080/15476910802019045