What are beta-glucans?
Beta-glucans are types of polysaccharides that have been shown to have effects on cholesterol and blood sugar levels and the immune system.
Where do beta-glucans come from? What food contains beta-glucans?They are found in cereals such as oats and barley, in some algae, mushrooms and yeast.
Their properties are related to their origin and chemical structure.
For example, it is the beta-glucans in mushrooms and yeast (beer or bread: Saccharomyces cerevisiae) that support the immune system.
Beta-glucans are polysaccharide chains consisting of several D-glucose units linked together by beta 1-3 and beta 1-4 bonds, with or without branching. The structure of beta-glucans depends on their origin and determines their health benefits:
Beta-glucans from oats and barley are composed of unbranched linear chains with beta 1-3 and beta 1-4 bonds. They are considered to be fibres. Beta-glucans from oats and barley have a prebiotic effect. In contrast, yeast or mushroom beta-glucans are composed of linear chains with beta 1-3 bonds and lateral branches with beta 1-6 bonds.
Therefore, when we talk about yeast and mushroom beta-glucans, we call them beta-1,3/1,6-glucans. The difference between the two lies in the length of the branches. Cereal beta-glucans have been demonstrated to have prebiotic properties owing to their ability to pass undigested through the gastro-intestinal Source: What types of beta-glucans are there, and what are their health benefits? (Pizarro, 2014)
Why are beta-glucans beneficial for health?
Beta-glucans are not digested or absorbed by our digestive system because humans do not have the enzymes to break them down. They arrive intact in the small intestine, where some of them act as dietary fibres and others as biologically active substances on the cells of the immune system.
Oat or barley beta-glucans to lower cholesterol and regulate blood glucose levelsCereal beta-glucans act as dietary fibre. They reduce plasma cholesterol and glucose concentrations and also improve parameters such as dyslipidaemia and insulin resistance.
Daily consumption of at least 3 g of beta-glucans from oats or barley may reduce LDL-cholesterol levels and therefore the risk of cardiovascular disease.
Yeast and mushroom beta-glucans to support the immune system
Yeast and mushroom beta-glucans have immunomodulatory properties. Their mode of action is complex as they interact with various receptors on different cell types and can act on both innate and adaptive immune responses. (De Marco Castro, 2020)
It has been proposed that beta-glucans interact directly at the Peyer's patches located in the membrane of the small intestine. Peyer's patches are areas in the intestines containing a cluster of many immune cells and are essential for initiating and regulating the immune response.
Beta-glucans are ingested by macrophages that participate in activating other cells involved in the immune system, enhancing antimicrobial activity against viruses, bacteria, yeast, and fungi.
Besides, 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 yeast beta-glucans
Beta-glucans and the immune system to prevent flu and colds
Several studies have been published on the role of beta-glucans from fungi and yeast in treating and preventing recurrent respiratory infections such as the common cold or flu in children, adults, and athletes. Respiratory infections are common at all ages, and some people may have up to 6 episodes per year.
Clinical studies using beta-glucans obtained from the yeast Saccharomyces cerevisiae have shown that they help reduce the recurrence of respiratory tract infections, the severity of their symptoms, and decrease episodes of allergy and allergic rhinitis. (Jesenak, 2017) Supplementation with different doses of yeast beta-glucans (Yestimun®) for 24 or 26 weeks has shown the following (Auinger, 2013; Graubaum, 2012):
- improves the immune system response to respiratory infections.
- helps to reduce the number of cold episodes It reduces the intensity of symptoms such as headache, sore throat, difficulty swallowing, hoarseness, cough, runny nose, and poor sleep due to the cold itself.
Supplementation with 250 mg/day of yeast beta-glucans for 4 weeks has also been shown to significantly reduce pollen allergy symptoms and their intensity by half (Pizarro 2014).
Beta-glucans and intense physical exercise
Regular physical exercise has positive effects on the immune system. However, prolonged, high-intensity exercise has negative consequences on immunity.
Therefore, the immunomodulatory activity of beta-glucans has been studied in athletes. A double-blind controlled trial of 75 marathon runners showed that 250-500 mg/day of yeast beta-glucans for 4 weeks after participation in a marathon significantly reduced the frequency of respiratory tract infections.
The treated group also observed a reduction in the feeling of fatigue. The authors of the study suggest that beta-glucans can support the immune system's proper functioning after intense exercise. (Talbott, 2009)
Beta-glucans with vitamin C
Beta-glucans act synergistically with vitamin C to improve the immune response to infections. Joint supplementation of these two nutrients is more effective than vitamin C alone in reducing respiratory infections in children and athletes (San Mauro-Martín, 2015).
How much beta-glucans to take?
To contribute to the immune system's proper functioning, the daily dose of yeast beta-glucans used in the various clinical studies is between 100 and 900 mg. To maintain normal cholesterol and blood sugar levels, a daily dose of 3 and 4 g respectively of oat or barley beta-glucans is recommended.
Are beta-glucans from yeast safe?
According to the European Food Safety Authority (EFSA), the consumption of Saccharomyces cerevisiae yeast is common in bakery products and homebrew populations. Regarding the use of yeast beta-glucans in food supplements,
EFSA allows a maximum of 1275 mg/day for adults and children over 12 years and 675 mg/day for children under 12 years. As yeast or mushroom beta-glucans modulate the immune system, they are not recommended for people taking immunosuppressants.
Auinger A, Riede L, Bothe G, Busch R, Gruenwald J. Yeast (1,3)-(1,6)-beta-glucan helps to maintain the body's defence 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 y Gotteland R, Martín. ß-glucanos: ¿qué tipos existen y cuáles son sus beneficios en la salud?ß-glucans: what types exist and what are their health benefits? Rev. chil. nutr.