Abstract
Euglena gracilis produce high amounts of algal β-1,3-glucan, which evoke an immune response when consumed. This study investigated the effect of supplementation with a proprietary Euglena gracilis fermentate (BG), containing greater than 50% β-1,3-glucan, on immune function as measured by self-reported changes in upper respiratory tract infection (URTI) symptoms. Thirty-four healthy, endurance-trained participants were randomized and received either 367 mg of BG or placebo (PLA) for 90 days. Symptoms were assessed by the 24-item Wisconsin Upper Respiratory Symptom Survey and safety via clinical chemistry, hematology, vitals, and adverse event reporting. Participants supplemented with BG over 90 days reported fewer sick days (BG: 1.46 ± 1.01; PLA: 4.79 ± 1.47 days; p = 0.041), fewer URTI symptoms (BG: 12.62 ± 5.92; PLA: 42.29 ± 13.17; p = 0.029), fewer symptom days (BG: 5.46 ± 1.89; PLA: 15.43 ± 4.59 days; p = 0.019), fewer episodes (BG: 2.62 ± 0.67; PLA: 4.79 ± 0.67; p = 0.032), and lower global severity measured as area under curve for URTI symptoms (BG: 17.50 ± 8.41; PLA: 89.79 ± 38.92; p = 0.0499) per person compared to placebo. Sick days, symptoms, and global severity were significantly (p < 0.05) fewer over 30 days in the BG group compared to PLA. All safety outcomes were within clinically normal ranges. The study provides evidence that supplementation with a proprietary Euglena gracilis fermentate containing greater than 50% β-1,3-glucan may reduce and prevent URTI symptoms, providing immune support and protecting overall health.