Effects of fermented soybean supplementation on secretory immunoglobulin A, myeloperoxidase, and antioxidant capacity: a randomised, placebo-controlled dietary intervention trial

Immune health and antioxidant defence play critical roles in protecting the body against infections, oxidative stress and inflammation. Both innate and adaptive immune responses are influenced by nutrition and diet, while antioxidants help maintain cellular homeostasis by mitigating oxidative damage. Fermented soybean (FSB) is rich in bioactive compounds like isoflavones and peptides, which have been shown to support immune function and antioxidant capacity. A randomised, placebo-controlled, 12-week intervention trial was performed on FSB supplementation The effects of FSB on immunological function and antioxidant status were evaluated at baseline and at weeks 4, 8, and 12. FSB intervention group demonstrated significantly higher secretory immunoglobulin A and myeloperoxidase levels compared to the baseline and placebo groups (p < 0.05). Over the course of the trial, salivary total antioxidant capacity increased significantly (p < 0.05). Our findings indicated FSB improved innate immunological and mucosal function, as well as antioxidant defence. FSB may serve as a functional food for enhancing immune support and regulating antioxidant status, particularly for younger individuals and specific populations at risk of infection. The study was registered on 29 July 2024 at clinicaltrials.gov (NCT06524271).