It seems logical: exercise generates free radicals, free radicals are bad, so athletes should take lots of antioxidants. But this intuitive reasoning is wrong — and understanding why is one of the most important lessons in sports nutrition. Welcome to the antioxidant paradox and the principle of hormesis.
Hormesis: The Dose Makes the Medicine
Hormesis is the phenomenon where a low or moderate dose of a stressor produces a beneficial adaptive response, even though a high dose would be harmful. Exercise is a classic example: the temporary oxidative stress of training is not merely tolerated — it is the signal that tells your body to get stronger. The reactive oxygen species (ROS) produced during exercise activate NRF2 and other adaptive pathways that build antioxidant defenses, mitochondria, and resilience.
How Over-Supplementing Backfires
Here is the paradox: if you flood your system with high-dose antioxidants (large amounts of vitamin C and E, for example) around your workouts, you can neutralize the ROS signal before it does its job. Several well-known studies found that heavy antioxidant supplementation blunted key training adaptations — including mitochondrial biogenesis and improvements in insulin sensitivity. In effect, you can supplement away some of the benefits you trained for.
Why Whole Foods Are Different
This does not mean antioxidants are bad — it means context and dose matter. Whole foods deliver antioxidant and NRF2-activating compounds in moderate, balanced amounts alongside fiber and other nutrients. They support health without the sledgehammer effect of isolated mega-doses. This is why our guidance emphasizes NRF2 foods and compounds like sulforaphane that activate your own defenses rather than simply dumping antioxidants into the system.
Practical Guidelines for Athletes
- Get antioxidants from food, not routine high-dose pills around training.
- Avoid mega-dosing vitamin C and E chronically unless directed by a professional for a specific reason.
- Time any supplements thoughtfully — away from the key adaptation window if used.
- Respect recovery as the real driver of adaptation; see overtraining and oxidative stress.
The smartest athletes work with their biology, not against it. Support NRF2 through training and food, and let the beneficial stress of exercise do its job. Return to the complete guide to NRF2 for athletes for the full picture.
This article is for educational purposes only and is not medical or professional training advice. Individual responses to exercise and nutrition vary. Consult a qualified healthcare provider or sports professional before making significant changes to your training, diet, or supplement routine — especially if you have a medical condition or take medication.
Frequently Asked Questions
Are antioxidant supplements bad for athletes?
Not inherently, but routine high-dose antioxidant supplements (especially large amounts of vitamin C and E) taken around training can blunt beneficial adaptations. The issue is dose and timing. Getting antioxidants from whole foods avoids this problem while still supporting health.
What is hormesis in simple terms?
Hormesis is the idea that a moderate dose of a stressor triggers a beneficial adaptation, even though too much would be harmful. Exercise is a prime example: the mild oxidative stress of training signals your body to build stronger defenses and more mitochondria.
Which supplements are most likely to blunt training gains?
Research has focused on high doses of vitamin C (often around 1000 mg) combined with vitamin E taken around workouts, which have been shown to interfere with some endurance and metabolic adaptations. Whole-food antioxidants and NRF2 activators like sulforaphane are not associated with the same concern.
So should I avoid all supplements as an athlete?
No — some supplements (like protein, creatine, or addressing a diagnosed deficiency) are useful and evidence-based. The specific caution is about routine high-dose antioxidant vitamins around training. Focus on a food-first approach and use targeted, evidence-based supplements thoughtfully.