The effect of antioxidants on exercise performance
Antioxidants are omnipresent: food, healthcare products, skin care products, cosmetics, supplements. As we cannot escape them, we think they are essential for our general good health and for the wellbeing of our body and cells. Antioxidants protect our cells from molecules known as reactive oxygen species (ROS).
But what is their effect on the performance of a high performance athlete? Let us have a look at the very simplified definitions first:
Free radicals are highly reactive molecules with an unpaired electron in their outer orbital. They try to compensate the free spot in their orbital by attacking healthy cells and stealing one of their electrons. By attacking muscle cells for example, the muscle fibre can be damaged resulting in a loss of performance.
Antioxidants are molecules which will prevent this attack by giving one of their electrons to the free radical, turning it into a non-reactive species. During exercise, the production of these ROS is increased, and the body’s capacities of antioxidant defences could be overwhelmed. Cellular components could be damaged and thus performance could be reduced, associated with exhaustion. Yet, over the last decade, evidence has shown that one amongst many other functions of ROS is to be a signal for training adaptation. For athletes, this is a very important and crucial point.
The body has many different mechanisms to compensate the excessive oxidation which might also take place during exercise:
- Dietary antioxidants can only be used once as antioxidants: this means we need a large amount of exogenous antioxidants for them to have an effective impact (Powers et al, 2008).
- The antioxidant enzymes in our bodies on the other hand, can be used repeatedly and their number increases with training: for example, superoxide dismutase, glutathione peroxidase. The more you train, the more you will produce these enzymes.
Many studies have indicated that the more exogenous high dose antioxidants you take (supplements), the more the signal for the adaptations will be dysregulated and the increased production of antioxidant enzymes is reduced.
In other words, there is no evidence that exercise requires antioxidant supplementation, neither will the recovery be enhanced with these supplements. On the contrary, antioxidant supplementation in high doses can even reduce the very interesting training induced adaptations of our defence system and reduce performance.
Therefore, go for foods naturally packed with antioxidants: seasonal and regional colourful fruits and vegetables (with a preference for organic food), nuts and seeds, herbs, and spices. The food first philosophy remains intact!
Eat at least 400-600g of fruits and vegetables per day (the more colourful the better). Nutrients with antioxidant activity and the most important foods containing these:
- Vitamin C: leafy greens, broccoli, brussels sprouts, kiwi, lemon, strawberries, bell peppers, potatoes
- Vitamin E: nuts, seeds, oil
- Carotenoids: apricots, asparagus, carrots, bell peppers, all green, orange, and yellow fruits and vegetables
- Selenium: brazil nuts, fish, shellfish, brown rice
- Zinc: beef, poultry, seeds, legumes, cashews
- Phenolic compounds: Quercetin (apples, red wine, onions), catechins (tea, cocoa, berries), resveratrol (red and white wine, grapes, peanuts, berries), coumaric acid (spices, berries), anthocyanins (blueberries, strawberries)
Clinical Sports Nutrition, fourth edition; Louise Burke and Vicki Deakin, McGraw-Hill Education
Micronutrition, santé et performance; Denis Richl, De Boeck
König D, Wagner KH, Elmadfa I, Berg A. Exercise and oxidative stress: significance of antioxidants with reference to inflammatory, muscular, and systemic stress. Exerc Immunol Rev. 7:108-33, 2001.
Powers, S.K., and M.J. Jackson (2008). Exercise-induced oxidative stress: cellular mechanisms and impact on muscle force production. Physiol. Rev. 88:1243-1276.
Powers, S.K., L.L. Ji, A.N. Kavazis, and M.J. Jackson (2011). Reactive oxygen species: impact on skeletal muscle. Compr. Physiol. 1:941-969.