Low-dose of yeast beta-glucan on respiratory symptoms and psychological well-being in moderately stressed adults

Yeast beta-glucan (YBG) is an immunomodulatory polysaccharide that enhances host defense, but optimal dosing for respiratory and psychological benefits requires investigation. This 12-week randomized, double-blind, placebo-controlled trial (ISRCTN 48336189) enrolled 198 moderately stressed adults (PSS-10 scores: 14-26) assigned to placebo, low-dose YBG (120 mg), or moderate-dose YBG (204 mg) daily. The primary outcome was upper respiratory tract infection symptom severity measured by WURSS-21. Both YBG doses improved symptoms compared with placebo (adjusted mean change, 95% CI: placebo +3.42 [0.91 to 5.93]; 120 mg -2.27 [-4.82 to 0.28]; 204 mg -3.51 [-6.06 to -0.96]), with only 204 mg exceeding the minimal clinically important difference. Both doses reduced negative mood states (<i>p</i> < 0.001), with no safety concerns observed. These findings suggest that YBG may support respiratory and emotional health in stressed populations, with 204 mg demonstrating the most consistent clinically meaningful effects.