A Pilot Randomized Controlled Trial on the Effects of Selenium Supplementation Combined with Exercise on Body Composition and Selenium Bioactivity

Introduction: Selenium (Se) is a crucial trace element that plays an important role in fat metabolism and muscle building. Selenoproteins, such as glutathione peroxidase (GPx) and selenoprotein P (SEPP), are key examples of Se bioactive proteins that contribute to overall physiological processes. In addition, exercise is well known for its beneficial effects on body composition. However, limited data exist regarding the effectiveness of Se supplementation combined with exercise on changes in body composition and Se bioactivity. This pilot randomized controlled trial aimed to determine the effects of Se supplementation combined with exercise on body composition and Se bioactivity, as indicated by GPx and SEPP levels. Methods: A total of 40 participants were recruited and allocated into two groups: an intervention group (n = 20) that received 200 µg of Se daily combined with regular exercise for 12 weeks, and a control group (n = 20) that performed regular exercise alone without Se supplementation for 12 weeks. Body composition was assessed using gold-standard and bioelectrical impedance methods, including BOD POD and InBody270. GPx and SEPP concentrations were determined using High-Performance Liquid Chromatography–Inductively Coupled Plasma Mass Spectrometry. Results: The results showed that at the endpoint, participants in the intervention group had a significantly lower percentage of body fat compared with the control group (p < 0.05). In addition, fat-free mass, GPx activity, and SEPP concentrations in the intervention group were significantly higher than those in the control group (p < 0.05). There were no significant differences in dietary habits between groups, except for Se intake, which was significantly higher in the intervention group at the endpoint (p < 0.05). Conclusions: Se supplementation combined with exercise was effective in improving body composition by reducing body fat percentage, increasing fat-free mass, and enhancing Se bioactivity compared with exercise alone.