What are beta-glucans?
Beta-glucans are a type of polysaccharide for which effects on cholesterol, blood glucose, and the immune system have been proposed.
Where are beta-glucans found?
They are found in cereals such as oats and barley, in algae, fungi, and yeasts. Their properties are related to their chemical structure, origin, molecular weight, and solubility, beta-glucans from fungi and yeasts (from beer or bread: Saccharomyces cerevisiae) that act on the immune system.
Structure of beta-glucans
Beta-glucans are polysaccharide chains consisting of several glucose units linked together through beta 1-3 and beta 1-4 bonds, with or without branches. The structure of beta-glucans depends on where they come from and determines their health benefits.
Oat and barley beta-glucans are composed of unbranched linear chains with beta 1-3 and beta 1-4 bonds, whereas yeast and fungal beta-glucans are composed of linear chains with beta 1-3 bonds and side branches with beta 1-6 adhesives.
Therefore, when reference is made to yeast and fungal beta-glucans, they are referred to as beta-1,3/1,6-glucans. The difference between the two is in the length of the branches, which are longer in yeast.
What are the health properties of beta-glucans?
Beta-glucans are neither digested nor absorbed in our digestive system because humans do not have enzymes to degrade them. So they arrive intact in the small intestine where they act, some as dietary fiber and others as biologically active substances on the cells of the immune system.
Beta-glucans from cereals (oat, barley): cholesterol and glucose
In cereal beta-glucans, they act as dietary fiber reducing plasma concentrations of cholesterol and glucose and improving parameters such as dyslipidemia and insulin resistance. Daily consumption of at least 3 g of beta-glucans from oats or barley can reduce LDL-cholesterol levels and consequently reduce the risk of cardiovascular disease.
Yeast and mushroom beta-glucans for the immune system
Yeast and fungal beta-glucans exhibit immunomodulatory properties. Their mode of action is quite complex because they interact with different cell types and act on innate and adaptive immune responses. (De Marco Castro, 2020)
It has been proposed that they interact directly with Peyer’s patches, located in the small intestine membrane. Or they can be ingested by the macrophages with subsequent activation of other cells involved in the immune system, improving antimicrobial activity against viruses, bacteria, yeasts, and fungi.
In addition, beta-1,3/1,6-glucans induce leukocyte activation, increase the number of Th1 lymphocytes, balance the Th1/Th2 ratio, modulate antibody production, and produce anti-inflammatory mediators. (Bashir, 2017)
Clinical studies with beta-glucans
Beta-glucans and immune system to prevent flu and cold
Several published studies on the role of fungal and yeast beta-glucans in the treatment and prevention of recurrent respiratory infections such as the common cold or flu in children, adults, and athletes.
Clinical studies conducted with beta-glucans obtained from the yeast Saccharomyces cerevisiae have been shown to reduce recurrent respiratory tract infections and the severity of their symptoms and reduce allergy and allergic rhinitis episodes. (Jesenak, 2017)
Respiratory infections are the most common type of infection at any age, with some people presenting up to 6 episodes per year. Taking a supplement with different doses of yeast beta-glucans (Yestimun®) for 24 or 26 weeks has shown the following (Auinger, 2013; Graubaum, 2012):
- improve the immune system’s response to respiratory infections
- reduce the number of episodes of the common cold
- reduce the intensity of symptoms such as headache, sore throat and difficulty in swallowing, hoarseness, cough, runny nose, and poor sleep quality due to the cold itself
Supplementation with 250 mg/day of yeast beta-glucans for 4 weeks has also been shown to significantly reduce overall pollen allergy symptoms and intensity by half (Pizarro 2014).
Beta-glucans and intense physical exercise
Regular physical exercise has positive effects on the immune system. However, prolonged and high-intensity physical activity has negative consequences on immunity.
Therefore, the immunomodulatory activity of beta-glucans has also been studied in athletes.
A double-blind, controlled trial conducted with 75 marathon runners showed that consumption of 250 to 500 mg/day of yeast beta-glucans for 4 weeks after participating in a marathon significantly reduced the frequency of respiratory tract infections. The treated group also improved feelings of fatigue, tension, and stamina, suggesting that beta-glucans can improve immunity after intense exercise. (Talbott, 2009)
Beta-glucans and vitamin C
Beta-glucans act synergistically with vitamin C to improve the immune response to infections. Joint supplementation of both nutrients is more effective than vitamin C alone in reducing respiratory infections in children and athletes (San Mauro-Martín, 2015).
What dose of beta-glucans is advisable to take?
The proven daily dose for yeast beta-glucans in different clinical studies with children and adults ranges from 100 to 900 mg for immune system enhancement.
It’s recommended a daily dose of 3 and 4 g respectively of beta-glucans from oats or barley to maintain normal cholesterol and blood glucose levels.
Safety of yeast beta-glucans
According to the European Food Safety Authority (EFSA), the consumption of Saccharomyces cerevisiae yeast is common in the population through bakery products and craft beer without any risk of allergy. Therefore, it concludes that the consumption of yeast beta-glucans is safe for humans.
Regarding the use of yeast beta-glucans in food supplements, EFSA authorizes a maximum of 1,275 mg/day for adults and children over 12 years of age and 675 mg/day for children under 12 years of age.
As yeast or mushroom beta-glucans modulate the immune system, it is not recommended for people taking immunosuppressants.
Auinger A, Riede L, Bothe G, Busch R, Gruenwald J. Yeast (1,3)-(1,6)-beta-glucan helps maintain the body’s defense against pathogens: a double-blind, randomized, placebo-controlled, multicentric study in healthy subjects. Eur J Nutr. 2013 Dec;52(8):1913-8.
Bashir KMI, Choi JS. Clinical and Physiological Perspectives of β-Glucans: The Past, Present, and Future. Int J Mol Sci. 2017 Sep 5;18(9):1906.
De Marco Castro E, Calder PC, Roche HM. β-1,3/1,6-Glucans and Immunity: State of the Art and Future Directions. Mol Nutr Food Res. 2020 Mar 29:e1901071.
Graubaum H, Busch R, Stier H and Gruenwald J, “A Double-Blind, Randomized, Placebo-Controlled Nutritional Study Using an Insoluble Yeast Beta-Glucan to Improve the Immune Defense System,” Food and Nutrition Sciences, Vol. 3 No. 6, 2012, pp. 738-746. DOI: 10.4236/fns.2012.36100.
Jesenak M, Urbancikova I, Banovcin P. Respiratory Tract Infections and the Role of Biologically Active Polysaccharides in Their Management and Prevention. Nutrients. 2017 Jul 20;9(7):779.
Pizarro C, Sebastián; Ronco M, Ana María and Gotteland R, Martín. ß-glucans: what types exist and what are their health benefits?Rev. chil. nutr. [online]. 2014, vol.41, n.4, pp.439-446.
San Mauro-Martín, Garicano-Vilar E. Role of vitamin C and beta-glucans on the immune system: review. Rev Esp Nutr Hum Diet. 2015;19(4):238-245.
Talbott S, Talbott J. Effect of BETA 1, 3/1, 6 GLUCAN on Upper Respiratory Tract Infection Symptoms and Mood State in Marathon Athletes. J Sports Sci Med. 2009 Dec 1;8(4):509-15.