Beta-glucans

What are beta-glucans?

Beta-glucans are a type of fiber found in the cell walls of cereals, algae, bacteria, and fungi. Their natural functions range from glucose storage to cellular and whole-plant structural integrity and to cell protection. Beta-glucans can be taken as a supplement or consumed as part of the diet, with the richest dietary sources being oats, barley, oyster mushrooms, and shiitake mushrooms. All beta-glucans consist of chains of glucose molecules linked via β-glycosidic bonds, but the chain length, branching, and types of β-linkages can vary, leading to differences in biological activity and physical characteristics. For example, cereal beta-glucans are soluble, consisting of unbranched chains of glucose units linked with a mixture of β-(1,3) and β-(1,4) bonds. On the other hand, fungal beta-glucans can be soluble or insoluble, and their glucose units are linked with β-(1,3) bonds, with or without branches attached via β-(1,6) bonds. While beta-glucans from oats and barley demonstrate some favorable effects on metabolic health, beta-glucans from yeasts and mushrooms are better known for their immune-modulating properties.

What are beta-glucans’ main benefits?

The beta-glucans found in cereals are the most thoroughly researched type, and their benefits appear similar to other kinds of soluble dietary fiber. In people with dyslipidemia, beta-glucans from oats or barley may provide small reductions in LDL cholesterol and total cholesterol. These beta-glucans also promote satiety and are linked to a small degree of weight loss. When included in a carbohydrate-containing meal, beta-glucans from oats and barley may lower the postmeal increase in blood glucose and insulin. Although reductions in fasting blood glucose and hemoglobin A1c (HbA1c) have been reported in people with type 2 diabetes, these effects have tended to be small enough that their clinical relevance is questionable. Beta-glucans are found on the surface of potentially pathogenic microorganisms like bacteria or yeasts, which means the presence of these beta-glucans in the body can signal to the immune system that a pathogen is present and it’s time to mount an immune response. When fungal beta-glucans are supplemented directly, the same effect may be achieved without the infective pathogen. Accordingly, preliminary research has tended to report that fungal beta-glucans may enhance immune function, which could be useful in a variety of contexts.

What are beta-glucans’ main drawbacks?

Cereal and fungal beta-glucans taken orally are generally reported to be safe and well tolerated, and most research has not identified any major side effects associated with the use of beta-glucans. Possible side effects are generally gastrointestinal, including diarrhea, constipation, nausea, flatulence, or abdominal cramping. Due to the immune-stimulating properties of fungal beta-glucans, use in people with an autoimmune disease should warrant caution. Although this hasn’t been explored in clinical research, it’s theoretically possible that fungal beta-glucans could worsen autoimmunity. There’s a lack of research looking at whether beta-glucans are safe during pregnancy. It’s probably safe to assume that exposure to beta-glucans through food poses no harm.

How do beta-glucans work?

The metabolic effects of oat and barley beta-glucans are largely due to their physical properties as soluble, viscous dietary fibers. These beta-glucans can hold onto water, creating a gel-like consistency in the gastrointestinal tract. This can have many effects, including slower gastric emptying, reduced digestion and absorption of glucose, and enhanced elimination of bile acids which can have the downstream effect of lowering cholesterol. Fungal beta-glucans from yeast or mushrooms may produce immune-modulating effects by binding to pattern recognition receptors on immune cells in the gastrointestinal tract. This can lead to the initiation of an immune response by the innate immune system, which might include the activation of macrophages, neutrophils, and natural killer cells. Still, changes in the levels of immune cells or the compounds they produce (e.g., cytokines) are not consistently found. Lastly, interactions between beta-glucans and the gut microbiome may contribute to the effects of beta-glucans, in terms of both their metabolic effects and their immune-modulating effects. Preclinical research suggests that beta-glucans may have prebiotic properties, meaning they could promote the growth of beneficial microorganisms in the gut which may provide health benefits to the body. However, there’s currently no clinical research connecting the benefits of beta-glucans to microbiome modulation.