There may be such a thing as too much antioxidant supplementation.
Not everything the body calls stress is something we want to eliminate. Resistance training temporarily increases reactive oxygen species, or ROS. We tend to hear ROS and immediately translate the sequence as oxidative damage → antioxidants → good.
But ROS are not only damage. They are also signals. Part of the oxidative stress created by training participates in pathways that tell muscle something happened and it should adapt.
That makes high-dose antioxidant supplementation more interesting than the simplistic formula:
Antioxidants are good, therefore more antioxidants must be better.
The human evidence is mixed
In one randomized trial, participants taking 1,000 mg of vitamin C plus 235 mg of vitamin E daily showed attenuation of several exercise-responsive signaling pathways, including p38 MAPK, ERK1/2, and p70S6K. The same study did not find less muscle growth after ten weeks. Read the trial.
Other trials have produced more concerning outcomes. A small study in trained men found results suggesting that vitamin C and E supplementation could blunt some strength and hypertrophy adaptations. Read the study.
The necessary counterweight is that a systematic review and meta-analysis of randomized trials did not find a significant overall reduction in gains in strength or lean mass. Read the review.
The useful conclusion is not that antioxidant supplements always block progress. It is that suppressing more oxidative stress does not automatically produce a better physiological outcome.
Hormesis matters
Training works partly because we expose the body to a manageable stressor and force adaptation:
Training → stress and ROS → signaling → adaptation.
Aggressively suppressing the signal creates at least a plausible point where “recovery optimization” begins to interfere with the event we are trying to recover from.
This is why I am increasingly skeptical of supplements marketed simply as “everyone needs this antioxidant.” Vitamin E is essential; that does not mean every person benefits from supplemental vitamin E, much less a megadose. Deficiency, dietary intake, lipid status, and the reason for supplementing are separate questions.
My practical default is to correct an identified deficiency, eat an antioxidant-rich diet, and be more skeptical of megadosing isolated antioxidants merely because oxidative stress sounds frightening.
Sometimes the stress we are trying to eliminate is part of the signal we paid the gym to create.