Benefits
Helps maintain healthy LDL cholesterol (oat and barley beta-glucan)
About 3 g a day of oat or barley beta-glucan, eaten as part of a diet low in saturated fat and cholesterol, is the basis of an FDA-authorized health claim, and EFSA reached the same conclusion for oat beta-glucan in 2010. A meta-analysis of 28 randomized trials and a second of 58 found LDL about 0.25 and 0.19 mmol/L below control, with large differences from trial to trial and no change in HDL.
Smaller blood sugar rise after carbohydrate meals
In a meta-analysis of 103 single-meal comparisons in 538 people, adding oat beta-glucan to a carbohydrate meal cut the glucose response by 23% and the insulin response by 22%; material below 300 kg/mol molecular weight did not work. A pooled analysis of four 3 to 8 week trials in 350 adults with type 2 diabetes found fasting glucose 0.52 mmol/L and HbA1c 0.21 points lower.
Yeast beta-glucan and upper respiratory immune defense
A pooled analysis of 13 trials in healthy adults linked yeast beta-glucan with fewer upper respiratory infections, but its authors noted high heterogeneity and few studies. Individual trials show mixed results: a 299-person trial eased symptoms in the first week of a cold but did not reduce how many people caught one, and two 250 mg Wellmune trials did not reach statistical significance.
Gut bacteria shifts with high molecular weight barley beta-glucan
In a crossover trial in adults with mildly high cholesterol, 3 g a day of high molecular weight barley beta-glucan raised Bacteroides and lowered Firmicutes, while low molecular weight material changed nothing. A 3-week trial of 3.3 g a day of oat or barley beta-glucan in 14 young adults found stool frequency and weight unchanged. Neither trial showed a digestive benefit.
Mechanism of action
Viscous gel and bile acid binding
Oat and barley beta-glucan form a viscous gel in the gut that binds bile acids and reduces their reabsorption. The liver then draws on blood cholesterol to make new bile acids, which is the proposed basis of the cholesterol effect. Processing that breaks the fiber down to low molecular weight cuts viscosity, and in pooled meal trials low molecular weight oat beta-glucan lost its glucose effect.
Slower stomach emptying and glucose absorption
Viscous beta-glucan slows stomach emptying and the absorption of carbohydrate, which is thought to explain the smaller rise in blood sugar and insulin after a meal. The effect depends on eating the fiber with the carbohydrate meal.
Dectin-1 and CR3 receptor binding (yeast beta-glucan)
In laboratory studies, yeast beta-1,3/1,6-glucans bind the Dectin-1 and complement receptor 3 receptors on macrophages, neutrophils and NK cells, priming innate immune cells. Oat beta-1,3/1,4-glucan is not thought to act this way. This is a proposed mechanism; it has not been shown to prevent infections in trials.
Fermentation in the colon
Beta-glucans reach the colon largely intact and are fermented by gut bacteria into short-chain fatty acids. In the cited human trial, high molecular weight barley beta-glucan raised Bacteroides and lowered Firmicutes; an increase in Bifidobacterium or Lactobacillus was not reported.
Clinical trials
Meta-analysis of 28 randomized trials comparing at least 3 g a day of oat beta-glucan with a control, including in-house study reports from CreaNutrition AG (Whitehead et al. 2014, Am J Clin Nutr)
Pooled trials using 3.0 to 12.4 g a day for 2 to 12 weeks.
LDL cholesterol was 0.25 mmol/L lower (95% CI 0.20 to 0.30) and total cholesterol 0.30 mmol/L lower than control, with no effect on HDL cholesterol or triglycerides. Dose and duration did not change the result, and lowering was greater in people with higher starting LDL.
Systematic review and meta-analysis of randomized trials of at least 3 weeks (Ho et al. 2016, Br J Nutr)
58 trials, 3,974 participants; median dose 3.5 g a day.
LDL cholesterol was 0.19 mmol/L lower, non-HDL cholesterol 0.20 mmol/L lower and apoB 0.03 g/L lower than control. Heterogeneity was considerable (I-squared 79% for LDL and 99% for non-HDL), so the size of the effect varied a lot between trials.
Systematic review and meta-analysis of acute crossover feeding trials adding oat beta-glucan to carbohydrate test meals (Zurbau et al. 2021, Eur J Clin Nutr)
103 trial comparisons in 538 people with and without diabetes.
Glucose response (iAUC) fell by 23% and insulin response by 22%, with high certainty of evidence. Material above 300 kg/mol molecular weight worked and material below it did not. This measures single meals, not long-term blood sugar control.
Double-blind, randomized, placebo-controlled trial of 900 mg a day of brewer's yeast beta-1,3/1,6-glucan for 16 weeks in winter (Dharsono et al. 2019, J Am Coll Nutr)
299 generally healthy adults who reported at least three colds in the previous year.
The number of people with a clinically confirmed infection did not differ (71 on beta-glucan, 70 on placebo), and overall severity was similar. Severity of physical symptoms during the first week of an episode was lower on beta-glucan.
Double-blind, placebo-controlled trial of Wellmune yeast beta-1,3/1,6-glucan, 250 mg a day for 90 days in winter, with infections medically confirmed (Fuller et al. 2017, Nutrition)
100 community-dwelling adults aged 50 to 70; 49 per group completed.
There were 17 confirmed infections on Wellmune and 28 on placebo (odds ratio 0.55, 95% CI 0.24 to 1.26, P = 0.149), not statistically significant. Symptom days showed a trend (P = 0.067) and symptom severity did not differ. Interferon-gamma release from stimulated blood rose, a laboratory marker.
Randomized, double-blind, placebo-controlled 90-day trial of Wellmune, 250 mg a day, during the peak cold season (Fuller et al. 2012, Nutrition)
100 healthy adults (mean age about 21); 97 completed.
Days with cold symptoms tended to be fewer (198 versus 241, P = 0.06), which is not statistically significant. Of the severity scores, only the ability to breathe easily improved significantly.