In plain terms: WGP Beta-1,3/1,6-D-Glucan shows early signals in human research but the evidence is limited -- small trials, surrogate endpoints, or not yet independently replicated. It is an emerging area, not yet a proven one.
WGP Beta-1,3/1,6-D-Glucan
The evidence as the record states it
Four indexed randomized controlled trials of yeast beta-1,3/1,6-glucan for upper respiratory tract infection, with mixed results. Auinger 2013 (PMID 23340963, 900 mg/day, n=162): 25 percent fewer symptomatic common cold infections in the per-protocol population (p=0.041). Talbott 2012 (PMID 23378458, Wellmune 250 mg/day, n=77): reduced upper respiratory symptoms in stressed women. Fuller 2017 (PMID 28606567, Wellmune 250 mg/day, n=100): fewer confirmed infections (17 versus 28) but the difference was not statistically significant (p=0.149); symptom days showed a trend (p=0.067) and severity did not differ. Dharsono 2019 (PMID 30198828, 900 mg/day, n=299): the primary endpoint, global WURSS-21 severity, was not significant (p=0.5267); several secondary early-interval severity analyses were. Mah et al. (J Diet Suppl, 2020; PMID 30380356), 357 marathon runners on 250 mg/day for 91 days: the number and duration of URTI episodes did not differ; fewer symptom days only in the per-protocol analysis. Grade C: the registered primary outcomes of the larger trials were null, and the positive findings come from per-protocol and secondary analyses, so no well-designed trial shows a meaningful effect on its primary outcome. Pooled evidence: Zhong et al. (European Journal of Nutrition, 2021; PMID 33900466): systematic review and meta-analysis of 13 randomized trials in healthy subjects, incidence of upper respiratory tract infection OR 0.345 (95% CI 0.192 to 0.620), with fewer episodes and shorter duration. The authors state that high heterogeneity and the small number of trials mean more high-quality research is warranted, which is exactly why this record states no single studied dose.
Why Grade C and not Grade B
Grade C reflects early or limited human evidence -- small trials, surrogate endpoints, or preliminary findings not yet independently replicated. The evidence points in a promising direction but does not yet meet the standard for Grade B. A single well-powered, independently replicated trial with a meaningful endpoint would move this to Grade B or higher.
What would move this grade
A well-powered randomized trial with an objective, clinically meaningful primary endpoint and at least one independent replication would support Grade B or higher.
How this was studied
Form: Two non-interchangeable preparations: Wellmune yeast beta-1,3/1,6-glucan, and an insoluble yeast beta-glucan · Dose: 250 mg/day (Wellmune) or 900 mg/day (insoluble). There is no single studied dose. · Population: Healthy adults across 13 randomized trials in the pooled analysis · Duration: 4 to 26 weeks across trials · What is sold differs: Retail products state a beta-glucan milligram figure without naming the preparation. Evidence for the ingredient class does not transfer to a particular product, which is why this record refuses to state one studied dose.