Antioxidants Block Effects of Exercise


Research shows that antioxidants block some of the beneficial metabolic effects of exercise. Let’s take a look at why is it so.

The human body is in a constant balancing act. There are external stressors, to which the body has to regularly adapt. Exercise is one such stressor. This is a breaking-down and building-up process. The aim of high-intensity training is to invoke as much need for adaptation as possible without completely destroying the muscle—or as we say, “No pain, no gain.”

In this balancing act, there’s a “just right” or “Goldilocks” zone for upsetting the body. Too little stress and the system won’t realize that it needs to adapt to its environment. Too much stress and you come to the point of injury. In the case of training, the goal is to learn how your body reacts by taking two steps forward and one step back. This way, you’re pushing the limits, but taking time for recovery. If you don’t allow for sufficient recovery, this can lead to an overreaching, non-functional or over-training syndrome— both of which can take weeks to months to recover from.

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It’s known that intense exercise causes remarkable increases in free radicals that can potentially damage tissues.


One of the physiologic mechanisms that encourages adaptations to the environment is “redox biology.” Redox stands for reduction-oxidation, which is the transfer of electrons between molecules. Unstable reactive oxygen molecules or “free radicals” have an unpaired electron that stimulates oxidation reactions with other molecules such as proteins, fats, cholesterol and DNA. These reactions may cause tissue damage. Nevertheless, these reactions are also critical to our survival. For example, our immune cells produce free radicals to eliminate intruders such as bacteria.

Our bodies also have an elaborate system of antioxidants that manage these reactions so they don’t cause more harm than good. The antioxidants in our bodies include many different enzymes and micronutrients that scavenge and eliminate free radicals mostly through “reduction” reactions.

It’s known that intense exercise causes remarkable increases in free radicals that can potentially damage tissues. If you are deficient in dietary and systemic antioxidants such as vitamins E and C, uric acid, ubiquinone, carotenoids, glutathione and polyphenols like resveratrol, you could be at greater risk for free radical damage of your muscle tissue. Moreover, the accumulation of free radicals in contracting muscle can result in inhibition of force production and early fatigue. However, low physiological levels of free radicals are necessary for normal force production in muscle.

Perhaps we shouldn’t just take tons of antioxidants to block all of the free radical damage that we can. We should never forget that our bodies are in a constant state of balance. Our body can only make adaptations when it sees a shift in that balance. The production of free radicals due to the stress of intense training tells your muscle cells that it’s time to adapt and strengthen in order to avoid damage from future stress. The free radicals do this through activation of genes and enzymes that lead to improvements in lean muscle. Even though much of the research on the oxidative stress of exercise is done in models of aerobic endurance exercise, some have examined its role in muscle-building anaerobic exercise.

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Aim to eat fresh vegetables and fruits every day to maintain the ideal level of antioxidants.


One of the ways in which lean muscle is improved is through the actions of insulin-like growth factor 1 (IGF-1). Exercising muscle produces IGF-1, which encourages further growth of lean muscle. Laboratory studies have showed that the production of free radicals is essential to the function of IGF-1 in lean muscle growth. When antioxidants are applied to muscle cells in the laboratory, IGF-1’s function is obliterated.

Although high-intensity exercise can produce numerous free radicals, evidence is overwhelmingly in support of its health benefits. For example, it’s well known that exercise improves sensitivity to insulin. Insulin is essential for improving lean muscle. Exercise seems to increase insulin sensitivity through mechanisms that depend on the formation of free radicals. Moreover, the increase in insulin sensitivity after physical exercise is almost entirely abrogated by daily ingestion of supraphysiologic doses of the commonly used antioxidants vitamin C and vitamin E. Therefore, antioxidant supplementation blocks some of the beneficial metabolic effects of exercise.

Studies also show that your muscle cells have to experience free radical oxidative stress to be able to increase their natural ability to resist oxidative stress. To say it differently, exposure to free radicals automatically strengthens the cells to resist free radicals. The same goes in reverse—if you don’t stress the cells, they lose the ability to resist stress. This is a natural consequence. If you don’t use it, you lose it! A balance between free radical production and antioxidant defense mechanisms seems to represent a vital component of many adaptive responses in skeletal muscle, as well as hypertrophy and atrophy. It seems that if the production of free radicals is ideal (i.e., a little higher than basal levels), the adaptive response is hypertrophy; but if the levels of free radicals are significantly increased above basal ranges and antioxidant-defensive capability, there’s an atrophic response.

What’s interesting is that it was the lower dosed studies that actually showed improvement, while higher dosages of the vitamins had no effect or detriment to training.


Interestingly, the “Goldilocks” level of antioxidants have already been proven in human trials. There are several studies that compared vitamin A, C and E supplementation during high-intensity exercise in trained people. The results of these studies were mixed, with some showing improvement in performance and others with detriment. What’s interesting is that it was the lower dosed studies that actually showed improvement, while higher dosages of the vitamins had no effect or detriment to training. Another study confirmed that the combination of the antioxidants at high doses actually acted as “pro”-oxidants in a model of eccentric (negatives) arm curls.

Is moderation the secret to antioxidant success? The problem with all of the studies on antioxidants is the variability of the variables in the studies. There’s little consensus on dosing, timing and which antioxidant is best. Studies usually fail to account for the amount of antioxidants present in the participant’s diets. Some may eat more vegetables and fruits and have a basis of greater antioxidant levels. If you don’t eat enough vegetables and fruits, you may be at risk of  being vitamin deficient, and thus antioxidant deficient. It would be a good idea if the studies compared vitamin levels before and after supplementation, because in this way it could be discovered that those who were deficient see improvement, while those who aren’t may not respond, or have detriment to antioxidant supplementation. There’s a fine balance when it comes to any supplementation. More isn’t always better.

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Written by Camille Bennett

Camille Bennett is our nutrition expert interested in fitness diet and doesn’t run out of delicious ideas for healthy and nutritional meals.


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