NOW Foods Beta 1,3/1,6-D-Glucan 100 mg provides a highly purified yeast-derived beta-glucan polysaccharide — one of the most researched natural immune-modulating compounds available. Beta-glucans activate macrophages and neutrophils by binding to specific immune receptors (particularly Dectin-1 and CR3), priming these first-line immune defenders for faster, more effective response to pathogens without causing inappropriate immune activation. Research supports beta-glucan for enhancing immune surveillance, reducing the duration and severity of upper respiratory tract infections, and supporting immune function in athletes subject to post-exercise immune suppression. NOW Foods uses the 1,3/1,6 linkage pattern specifically — the form with the strongest evidence for immune modulation — at 100 mg per capsule, manufactured in their GMP-certified facility with purity verification.