Antioxidant supplementation during resistance training has no significant effect on muscle protein synthesis rates as measured by short-term isotope tracer methods, indicating that acute anabolic signaling changes do not result in altered net protein balance.

When you lift weights, your muscles produce molecules called ROS that act as signals to turn on protein-building pathways. Taking antioxidant supplements reduces these ROS signals, which lowers the activity of a key protein called p70S6K that helps start protein production. Even though this signal is weaker, the total amount of new muscle protein made stays the same because other pathways compensate. At the same time, antioxidants reduce the breakdown of old proteins by lowering another ROS-driven system, so the overall balance of protein building and breaking stays unchanged.