The term “beta-glucan” refers to a class of soluble fibers found in many plant sources. The best documented use of beta-glucan involves improving heart health; the evidence for benefit is strong enough that the FDA has allowed a “heart healthy” label claim for food products containing substantial amounts of beta-glucan. 1 Much weaker evidence supports the potential use of certain beta-glucan products for modifying the activity of the immune system.
Beta-glucan is not an essential nutrient. It is found in whole grains (especially oats, wheat, and barley) and fungi such as baker’s yeast, Coriolus versicolor , and the medicinal mushrooms maitake and reishi .
Different food sources contain differing amounts of the various chemical constituents collectively called beta-glucan. Grains primarily contain beta-1,3-glucan and beta-1,4-glucan. Fungal sources contain a mixture of beta-1,3-glucan and beta-1,6-glucan. Purified products containing only the 1,3 form are also available.
A substantial, if not entirely consistent, body of evidence indicates that beta-glucan, or foods containing it (especially oats), can modestly improve cholesterol profile . 2-11, 35 The most reliable benefits have been seen regarding levels of total cholesterol and LDL (“bad”) cholesterol. Modest improvements of up to 10% have been seen in studies. Possible improvements in HDL (“good”) cholesterol have only been seen inconsistently. It is thought that beta-glucan reduces cholesterol levels by increasing excretion of cholesterol from the digestive tract. This affects two forms of cholesterol: cholesterol from food, and, more importantly, cholesterol from the blood “recycled” by the liver through the intestines. However, virtually all studies involved oats and were conducted by manufacturers of oat products; independent confirmation remains minimal. 36
In addition, beta-glucan may help limit the rise in blood sugar that occurs after a meal. This could, in theory, offer heart-healthy benefits, especially in people with diabetes. 15-19
The other primary proposed use of beta-glucan products involves effects on the immune system. Test-tube , animal , and a few controlled studies in humans suggest that beta-glucans can alter various measurements of immune function. In the alternative medicine literature, these effects are commonly summarized as indicating that beta-glucan is an “immune stimulant.” This description, however, is an oversimplification. The immune system is extraordinarily complicated and, as yet, incompletely understood. At the current level of scientific understanding it is not possible to characterize the effects of beta-glucan more specifically than to say that it has “immunomodulatory” actions, or that it is a “biological response modifier.” These intentionally unsensational terms indicate that we merely know beta-glucan affects (modulates) immune function, not that it improves immune function.
Some of the immune-related effects seen in studies include alterations in the activity of certain white blood cells and changes in the levels or actions of substances, called cytokines, that modulate immune function.
Based on these largely theoretical findings, as well a small number of very preliminary human trials, 29-31 various beta-glucan products have been advocated for the treatment of conditions as diverse as allergic rhinitis , cancer , infections, and sepsis (overwhelming infection following major trauma, illness, or surgery). However, the evidence for actual clinical benefit remains highly preliminary.
One study failed to find that beta-1,3-glucan (in topical gel form) helpful for treatment of actinic keratosis, a form of sun-induced precancerous changes seen in aging skin . 32 Another study found that it had no significant effect on periodontal disease (gingivitis), an inflammation of the gums caused by bacteria found in dental plaques. 37
For improving total and LDL cholesterol, studies have found benefit with beta-glucan at doses ranging from 3 to 15 grams daily. However, benefits have been seen more consistently at the higher end of this range, and one carefully designed study found no benefit at 3 grams daily. 33
Beta-glucan products can contain molecules of various average lengths (molecular weight). Some manufacturers claim superior benefits with either high or low molecular weight versions. However, one study failed to find any difference between high molecular weight and low molecular weight beta-glucan for normalizing cholesterol and blood sugar levels. 34
Beta-glucan, as a substance widely present in foods, is thought to have a high margin of safety. However, if it really does activate the immune system, harmful effects are at least theoretically possible in people with conditions where the immune system is overactive. These include multiple sclerosis , lupus , rheumatoid arthritis , asthma , inflammatory bowel disease , and hundreds of others conditions. In addition, people taking immunosuppressant drugs following organ transplantation surgery could, in theory, increase their risk of organ rejection. However, there are no reports as yet to indicate that any of these hypothetical problems have actually occurred. Maximum safe doses in young children, pregnant or nursing women, or people with severe liver or kidney disease have not been established.
5. Jenkins DJ, Kendall CW, Vuksan V, et al. Soluble fiber intake at a dose approved by the US Food and Drug Administration for a claim of health benefits: serum lipid risk factors for cardiovascular disease assessed in a randomized controlled crossover trial. Am J Clin Nutr. 2002;75:834-839.
7. Keogh GF, Cooper GJ, Mulvey TB, et al. Randomized controlled crossover study of the effect of a highly beta-glucan-enriched barley on cardiovascular disease risk factors in mildly hypercholesterolemic men. Am J Clin Nutr. 2003;78:711–718.
10. Onning G, Wallmark A, Persson M, et al. Consumption of oat milk for 5 weeks lowers serum cholesterol and LDL cholesterol in free-living men with moderate hypercholesterolemia. Ann Nutr Metab. 2000;43:301-309.
11. Uusitupa MI, Ruuskanen E, Makinen E, et al. A controlled study on the effect of beta-glucan-rich oat bran on serum lipids in hypercholesterolemic subjects: relation to apolipoprotein E phenotype. J Am Coll Nutr. 1992;11:651-659.
14. Davy BM, Melby CL, Beske SD, et al. Oat consumption does not affect resting casual and ambulatory 24-h arterial blood pressure in men with high-normal blood pressure to stage I hypertension. J Nutr. 2002;132:394-398.
15. Braaten JT, Scott FW, Wood PJ, et al. High beta-glucan oat bran and oat gum reduce postprandial blood glucose and insulin in subjects with and without type 2 diabetes. Diabet Med. 1994;11:312-318.
17. Jenkins AL, Jenkins DJ, Zdravkovic U, et al. Depression of the glycemic index by high levels of beta-glucan fiber in two functional foods tested in type 2 diabetes. Eur J Clin Nutr. 2002;56:622-628.
24. Kirmaz C, Bayrak P, Yilmaz O, et al. Effects of glucan treatment on the Th1/Th2 balance in patients with allergic rhinitis: a double-blind placebo-controlled study. Eur Cytokine Netw. 2005;16:128-134.
25. Miyazaki K, Mizutani H, Katabuchi H, et al. Activated (HLA-DR+) T-lymphocyte subsets in cervical carcinoma and effects of radiotherapy and immunotherapy with sizofiran on cell-mediated immunity and survival. Gynecol Oncol. 1995;56:412-420.
27. Wakshull E, Brunke-Reese D, Lindermuth J, et al. PGG-glucan, a soluble beta-(1,3)-glucan, enhances the oxidative burst response, microbicidal activity, and activates an NF-kappa B-like factor in human PMN: evidence for a glycosphingolipid beta-(1,3)-glucan receptor. Immunopharmacology. 1999;41:89-107.
29. de Felippe Junior J, da Rocha e Silva Junior M, Maciel FM, et al. Infection prevention in patients with severe multiple trauma with the immunomodulator beta 1-3 polyglucose (glucan). Surg Gynecol Obstet. 1993;177:383-388.
30. Nakano H, Namatame K, Nemoto H, et al. A multi-institutional prospective study of lentinan in advanced gastric cancer patients with unresectable and recurrent diseases: effect on prolongation of survival and improvement of quality of life. Kanagawa Lentinan Research Group. Hepatogastroenterology. 1999;46:2662-2668.
34. Frank J, Sundberg B, Kamal-Eldin, A et al. Yeast-leavened oat breads with high or low molecular weight beta-glucan do not differ in their effects on blood concentrations of lipids, insulin, or glucose in humans. J Nutr. 2004;134:1384-1388.
35. Queenan KM, Stewart ML, Smith KN, et al. Concentrated oat beta-glucan, a fermentable fiber, lowers serum cholesterol in hypercholesterolemic adults in a randomized controlled trial. Nutr J. 2007 Mar 26. [Epub ahead of print]
37. Preus HR, Aass AM, Hansen BF, et al. A randomized, single-blind, parallel-group clinical study to evaluate the effect of soluble beta-1,3/1,6-glucan on experimental gingivitis in man. J Clin Periodontol. 2008;35:236-241.
Last reviewed August 2013 by EBSCO CAM Review Board
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