Dieting Nutrition

Are antioxidants good for athletes?

Over the last century, there’s been an explosion of new understanding with respect to the chemical workings of the human body, it’s processes, the foods we consume, and the interaction between them all. Years ago, people were finding that exercise and exposure to pollution created a lot of oxidative stress on the body by creating free-radicals, and that those compounds can potentially cause damage to cells and even be carcinogenic. So, logically, if you were to supplement your diet with antioxidants like Vitamin A, C, E and other antioxidant compounds, you should be able to reduce the threat of damage caused by oxidative stress and maybe even reduce your risk of cancer or heart disease. After all, eating a diet rich in those antioxidant chemicals (generally a diet rich in fruits and vegetables) is associated with much better health and lower risks of heart disease and cancer. And, there’s always the potential that if your body is under less stress from working out, that maybe your performance could be bolstered by taking supplemental antioxidants that will allow you to work out without causing as much cellular damage and shortening the time needed for recovery between challenging workouts.

Well, it appears more and more to be the case that current scientific research is finding that the exact opposite appears to be the case. Eating a diet high in natural antioxidants and antioxidant phytochemicals is great for your health, but supplementing with antioxidants appears to be detrimental to exercise performance and probably health generally.

Every week or two, I seem to be running across articles citing new studies that indicate that the oxidative stress sustained during endurance training is key to eliciting the positive adaptations that are the main aim of endurance training. That is, going out for a hard run or bike ride causes oxidative stress and the stress itself is at least in part key to improving fitness. Similarly, your body’s own regulation of its production of its own antioxidant chemicals is affected by exposure to oxidative stress. Expose yourself to oxidative stress and your body will become more adept at defending itself against the damage that occurs as a result of that exposure. Likewise, artificially flooding your system with antioxidant chemicals (i.e. supplemental antioxidants) kills your body’s production of those internal antioxidant systems. Interestingly, the oxidative stress also seems to be key to directly influencing performance by bringing about the physiological changes that make you fitter. For example, my attention was recently brought to the following study…


This review offers an overview of the influence of reactive species produced during exercise and their effect on exercise adaptation. Reactive species and free radicals are unstable molecules that oxidize other molecules in order to become stable. Although they play important roles in our body, they can also lead to oxidative stress impairing diverse cellular functions. During exercise, reactive species can be produced mainly, but not exclusively, by the following mechanisms: electron leak at the mitochondrial electron transport chain, ischemia/reperfusion and activation of endothelial xanthine oxidase, inflammatory response, and autooxidation of catecholamines. Chronic exercise also leads to the upregulation of the body’s antioxidant defence mechanism, which helps minimize the oxidative stress that may occur after an acute bout of exercise. Recent studies show a beneficial role of the reactive species, produced during a bout of exercise, that lead to important training adaptations: angiogenesis, mitochondria biogenesis, and muscle hypertrophy. The adaptations occur depending on the mechanic, and consequently biochemical, stimulus within the muscle. This is a new area of study that promises important findings in the sphere of molecular and cellular mechanisms involved in the relationship between oxidative stress and exercise.

And, interestingly, on a hormonal level, the fact that your body is being stressed may be more closely tied to the adaptations that occur as the result of training more than training may increase growth hormone or testosterone production. A recent study found a positive correlation between cortisol production (the stress hormone) and gains in muscle size in a strength training routine, whereas growth hormone and testosterone had little or no correlation with muscle size or strength gains.

Just like most things in your body, if you take over one of its systems and try to cause a certain change, your body will basically do the opposite of what you do to it. If you break or fracture a bone, your body responds by building it back again stronger. If you never lift weight, sustain impact, or become an astronaut in a weightless environment your bones become weak and easy to break. If you train hard, your body will get stronger. If you never exercise, your heart, muscles and nervous system get weak from lack of stimulation… If you take a bunch of daily vitamin C, E in supplemental form, then your body gives up its efforts to create its own antioxidants. In contrast, if you exercise regularly, the exposure to oxidative stress will make your body much better at defending against damages caused by oxidative stress.

The interesting thing is that it appears that consuming natural foods high in antioxidants and antioxidant forming compounds do not cause the same downregulation of internally originating antioxidants. Maybe because if you eat an orange or drink some grean tea, most of the antioxidant compounds are plant chemicals that aren’t as directly related or recognizable to your body as something like vitamin A, C and E and their derivatives. Plants have their own antioxidant systems to keep them protected from the stresses they face, and in eating them, we can augment our own by appropriating their defense systems. Whereas, if we pop vitamin C like candy, we’re killing our own defense systems.

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