How reliable is the labeling of a commercial phytosteroid product? A 12-week randomized double-blind training study

Phytosteroids like 20-hydroxyecdysone (20E) and diosgenin (DSG) have shown promising anabolic and performance-enhancing effects in in vitro, animal, and human studies. Combining phytosteroids is common in supplements, with early in vitro research suggesting additive effects via distinct signaling pathways. However, human studies on the combined effects of 20E and DSG are lacking. This study aimed to evaluate the anabolic and performance-enhancing potential of a commercially available 20E and DSG supplement.

Twenty-eight resistance-trained young men were recruited for this study. Participants were randomized into two groups: a 20E and DSG (EcDi) group, and a placebo (Plac) group. Both groups performed free-weight resistance training three times per week for 12 weeks. The EcDi group received a commercially available phytosteroid product three times a day (as recommended on the label), while the Plac group received a placebo product. Assessments were conducted at four time points (T0, T1 [4 weeks], T2 [8 weeks], T3 [12 weeks]) and included measurements of one-repetition maximum (1-RM) for the squat (SQ) and bench press (BP) exercises, as well as body weight (BW), fat-free mass (FFM), muscle mass (MM), fat mass (FM), and muscle thickness of the pectoralis major (PM) and the proximal, middle and distal regions of the anterior (i.e. M. rectus femoris and M. vastus intermedius) and lateral quadriceps femoris (i.e. M. vastus lateralis and M. vastus intermedius). Liver and kidney function, along with endocrine parameters, were measured via blood samples pre- and post-intervention. Additionally, the concentration of 20E and DSG in the product was measured by LC-MS/MS, and its biological activity was evaluated using C2C12 cells after the intervention. Data were analyzed using a linear mixed model (LMM).

Twenty-four participants completed the study successfully. Significant improvements in 1-RM SQ and BP were observed across both groups, indicating a time but no specific group effect. Similarly, significant time effects without group effects were found for FFM, MM, FM and muscle thickness (anterior quadriceps femoris at 30%, lateral quadriceps femoris at 50% and PM). Subsequent analyses of the supplement revealed that less than 1% of the claimed 20E concentration and 10.4% of the claimed DSG concentration were present in the capsules. In addition, no biological activity or hypertrophic effects were detected in the C2C12 cells.

This study demonstrated that the prescribed resistance training protocol resulted in significant anabolic and performance-enhancing effects that did not differ between groups. The lack of group-specific differences suggests that the tested phytosteroid supplement did not provide additional benefits. The significant discrepancy between the claimed and actual 20E and DSG concentration resulted in the lack of biological activity in C2C12 cells and likely contributed to the absence of measurable group-specific effects. To enhance the reliability of future phytosteroid research, we strongly recommend: (1) verification of active compound concentrations in supplements, its actual content and absence of potential contamination with prohibited substances, (2) confirmation of their biological activity using in vitro models. Implementing these measures will help to minimize inconsistencies and enhance the reliability of future studies on phytosteroids.