Beta-glucans are fibers (polysaccharides) that naturally occur in oats, barley, mushrooms, and yeast. Beta-1,3/1,6-D-glucans are a specific form of beta-glucans. The numbers refer to the way in which glucose molecules are bonded.

Beta-1,3/1,6-D-glucan is a natural polysaccharide extracted from the cell wall of yeast species such as Saccharomyces cerevisiae.

Beta-glucans can be found in oats, barley, baker's yeast (Saccharomyces cerevisiae), certain mushrooms (such as shiitake and reishi), and some seaweeds.

Grifola frondosa, better known as maitake or “the dancing mushroom,” naturally grows at the base of deciduous trees such as oak. This unique mushroom has been valued for centuries in Asian cuisine and traditional herbal medicine.