At a glance:
- Antioxidants neutralize free radicals produced during training, but moderate oxidative stress is an essential molecular signal for training adaptations.
- Research suggests that high doses of vitamin C and vitamin E may hinder muscle mass gains and training adaptations.
- The best way to get antioxidants is through a varied diet—berries, vegetables, nuts and whole grains.
- Supplements should only be considered if a deficiency has been identified, preferably on a doctor’s recommendation.
Antioxidants protect your body’s cells from the harmful effects of free radicals—and their importance increases during training. Intense physical exertion significantly increases the production of oxidative species in the body, which has brought antioxidants growing attention among athletes. In this guide, we look at what the science actually says about antioxidants in the context of training.
What are antioxidants, and how do they work during training?
Antioxidants are molecules that neutralize reactive oxygen species (ROS), which are produced naturally during metabolism. During training—particularly intense endurance or plyometric training—oxygen consumption increases severalfold, accompanied by a substantial rise in ROS production.
It is important to understand that not all reactive oxygen species are harmful. In moderate amounts, they are important signaling molecules that trigger adaptive processes: muscle protein synthesis, activation of mitochondrial enzymes and upregulation of the body’s own defense mechanisms. In other words, regular, moderate training acts as a kind of antioxidant: it increases the activity of the body’s endogenous antioxidants (e.g. superoxide dismutase, glutathione) (Gomez-Cabrera et al., 2008).
The body’s main antioxidant defenses:
– Endogenous enzymes: superoxide dismutase (SOD), catalase, glutathione peroxidase
– Micronutrients from food: vitamin C, vitamin E, beta-carotene, polyphenols, selenium, zinc
Fat burning and training involve the same metabolic processes—and moderate oxidative stress is an essential molecular signal in both, rather than simply a source of damage.
Do high doses of antioxidants help you achieve better training results?
This is one of the most debated topics in sports science. A landmark study showed that high daily doses of vitamin C and vitamin E (1000 mg vitamin C + 400 IU vitamin E) hinder the body’s health-promoting adaptations following training—particularly improvements in insulin sensitivity and mitochondrial adaptation (Ristow et al., 2009). Participants who took antioxidants did not gain the same metabolic benefits from training as the control group.
An 11-week double-blind controlled trial provided more specific findings: athletes who took vitamin C and vitamin E supplements showed smaller gains in muscle mass and less mitochondrial adaptation than the placebo group (Paulsen et al., 2014). A review confirms this trend: high-dose antioxidant supplements may interfere with training adaptations, particularly when taken immediately before or after a workout (Peternelj & Coombes, 2011).
Testosterone and training is another area in which hormonal adaptations are sensitive to external factors—similarly, supplements can affect the body’s natural adaptive processes.
Which food sources can provide enough antioxidants?
Most experts—including the World Health Organization (WHO)—recommend getting antioxidants primarily from a varied diet rather than supplements. The European Food Safety Authority (EFSA) has set the recommended daily intake for adults at 80–110 mg for vitamin C and 11–13 mg TE (α-tocopherol equivalents) for vitamin E—amounts that can readily be obtained from a normal mixed diet.
The best food sources of antioxidants:
| Nutrient | Rich sources |
|---|---|
| Vitamin C | Bell peppers, blackcurrants, rose hips, citrus fruits |
| Vitamin E | Nuts, seeds, olive oil, green vegetables |
| Beta-carotene | Carrots, sweet potatoes, pumpkin, spinach |
| Selenium | Brazil nuts, fish, eggs |
| Polyphenols | Bilberries, dark berries, green tea, dark chocolate |
What is functional training? reflects a holistic approach to the body—and the same philosophy applies to nutrition: a varied diet that includes plant foods provides a broad spectrum of antioxidants without the risks of supplements.
When might antioxidant supplements be justified?
Although routinely taking high doses is generally not recommended if you train, there are situations in which supplements may be considered:
- Dietary deficiency: in cases of severe calorie restriction, a limited diet or digestive disorders
- Recovery after illness: when oxidative stress is elevated for other reasons
- Extremely intense, high-volume training: e.g. ultra-endurance athletes competing on several consecutive days
Even in these cases, supplements are recommended only when an actual deficiency has been identified—preferably through a blood test and on a doctor’s recommendation (Powers & Jackson, 2008).
Practical advice: avoid high doses of vitamin C and vitamin E immediately before or after a workout. The moderate oxidative stress produced during training is a beneficial signal for your body—do not suppress it with supplements.
References
- Gomez-Cabrera MC, Domenech E, Viña J. (2008). Moderate exercise is an antioxidant: upregulation of antioxidant genes by training. Free Radical Biology and Medicine, 44(2), 126–131. PMID: 18182652
- Ristow M, Zarse K, Oberbach A, Klöting N, Birringer M, Kiehntopf M, Stumvoll M, Kahn CR, Blüher M. (2009). Antioxidants prevent health-promoting effects of physical exercise in humans. Proceedings of the National Academy of Sciences, 106(21), 8665–8670. PMID: 19433800
- Paulsen G, Cumming KT, Holden G, Hallén J, Sølie BR, Benestad HB, Raastad T. (2014). Vitamin C and E supplementation hampers cellular adaptation to endurance training in humans: a double-blind, randomised, controlled trial. Journal of Physiology, 592(8), 1887–1901. PMID: 24492839
- Peternelj TT, Coombes JS. (2011). Antioxidant supplementation during exercise training: beneficial or detrimental? Sports Medicine, 41(12), 1043–1069. PMID: 21780842
- Powers SK, Jackson MJ. (2008). Exercise-induced oxidative stress: cellular mechanisms and impact on muscle force production. Physiological Reviews, 88(4), 1243–1276. PMID: 18923182
Frequently asked questions
Are antioxidants beneficial for people who exercise?
Antioxidants from food support overall health and recovery. However, research suggests that high-dose supplements may interfere with adaptations to training, so choosing food sources over supplements is recommended.
When should you take antioxidants—before or after a workout?
Taking high doses of vitamin C and vitamin E immediately before or after a workout is not recommended, as they may inhibit the beneficial adaptation processes triggered by training. If you use supplements, take them with a meal in the morning instead.
Which foods contain the most antioxidants?
The richest sources include dark berries (bilberries, blackcurrants), bell peppers, rose hips, spinach, nuts, seeds and green tea. A varied diet of plant-based foods provides a broad spectrum of antioxidants.
Does vitamin C speed up recovery after a workout?
In amounts obtained from food, vitamin C supports collagen synthesis and immune function. Very high doses (over 1000 mg per day) are not recommended for people who exercise, as research suggests they may inhibit adaptations to training.
How can you tell if you need antioxidant supplements?
The best way is to have a blood test to identify any vitamin deficiencies. If you eat a varied diet, supplements are rarely necessary. Consult your doctor before using high-dose supplements.
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