Beta-glucans are a type of soluble fiber found in oats and barley, and mushrooms, as well as yeasts, bacteria, and algae. Beta-glucans are a key factor in the cholesterol-lowering effect of oats. As with other soluble fibers, beta-glucans lower circulating cholesterol levels by binding to dietary cholesterol, reducing its absorption, and by altering cholesterol metabolism, partly through effects on the gut microbiome.^1,2 A meta-analysis of results from 21 controlled trials that included a combined total of 1,120 participants with mildly elevated cholesterol levels found supplementing with a minimum of 3 grams per day of beta-glucan for at least three weeks led to reductions in total and LDL-cholesterol levels.³ In one placebo-controlled trial that included 191 subjects with borderline to very high LDL-cholesterol levels, taking 3 grams of beta-glucan daily for four weeks reduced LDL-cholesterol levels by 6% and cardiovascular risk scores by 8%.⁴ A placebo-controlled crossover trial that had 83 participants with moderately high cholesterol levels found LDL-cholesterol levels dropped 15.1%, total cholesterol levels decreased 8.9%, and non-HDL-cholesterol levels fell 12.1% after eight weeks of supplementing with 3 grams of beta-glucan daily.⁵

Beta-glucan is a fiber-type polysaccharide (complex sugar) derived from the cell wall of baker’s yeast, oat and barley fiber, and many medicinal mushrooms, such as maitake. Numerous experimental studies in test tubes and animals have shown beta-glucan to activate white blood cells.^6,7,8,9,10 In fact, there have been hundreds of research papers on beta-glucan since the 1960s.¹¹ The research indicates that beta-1,3-glucan, in particular, is very effective at activating white blood cells known as macrophages and neutrophils. A beta-glucan–activated macrophage or neutrophil can recognize and kill tumor cells, remove cellular debris resulting from oxidative damage, speed up recovery of damaged tissue, and further activate other components of the immune system.^12,13 Although the research in test tube and animal studies is promising, many questions remain about the effectiveness of beta-glucan as an oral supplement to enhance immune function in humans. Controlled trials are necessary to determine whether humans can benefit from beta-glucan, and in what amounts oral beta-glucan must be taken from meaningful effects.