Food-products are forever being fortified with antioxidants to the point where they’re now synonymous with a healthy diet. But just how beneficial is supplementation to a training athlete?
You’ve probably come across some of the supposed wonders of antioxidants. Anti-aging, disease prevention, lowering of blood pressure? But as usual there’s no explanation, no evidence, no real vindication of why they’re good for you just that they are.
This happens with all health-related fads as we the public demand that one wonder cure for everything. We’re spoon fed information, jump on the bandwagon and in next to no time we’re eating blueberries and cranberries by the dozen and drinking enough green tea to sink a ship.
So one would expect that a training athlete should consume more of these antioxidants because more usually means better, right?
Wrong. Well potentially anyway, and here’s why.
Putting the Anti in Antioxidants
Antioxidants are literally anti-oxidants, preventing the oxidation of other molecules. Oxidation of a molecule occurs when an electron is lost leaving the molecule in a reactive state.
These loose electrons are known as free radicals, whilst unbalanced molecules are known as reactive oxygen species (ROS) such as oxygen ions and peroxides. They are molecules or any chemical species that contain one or more unpaired electrons in their outer shell.
Damage occurs when a free radical or ROS comes into contact with another molecule. As they are highly reactive, the free radical or ROS will seek to pair itself with another electron in order to balance itself, drawing electrons away from other molecules which in turn become free radicals and ROS themselves, often producing a chain reaction.
Eventually a protein or lipid vital for the regulation of the cell will become damaged and the cell will lose some of its primary function. DNA too can be damaged creating cross-links which are essentially “kinks” in the DNA sequence, disrupting DNA replication, protein transcription and even causing cell death.
Antioxidants act sacrificially by binding with potentially damaging, free radicals and ROS without becoming reactive themselves. By removing these substances antioxidants can elongate the cell cycle, and this is the basis for their anti-aging effects.
During exercise contracting skeletal muscle produces free radicals and ROS as by-products of energy metabolism. Mitochondria are thought to be the predominant source of ROS production in muscles as the inner membrane is the site of an important part of energy metabolism – the electron transport chain (ETC).
The basics of the ETC are relatively simple. In essence it is a series of reduction-oxidation (redox) reactions in which a molecule (hydrogen carrier) gains an electron, reducing it, and then releases the electron soon after, oxidising it.
In total there are four known complexes with complexes I and III being known areas of electron leakage. Research suggests that between 2-5% of all oxygen consumed by mitochondria may undergo one electron reduction, generating superoxide a dangerous ROS.
Therefore during exercise when we require more energy and our oxygen consumption increases we produce more of this harmful superoxide. Exercise for too long or too hard and the muscle will become fatigued. Although fatigue can be contributed to a number of factors an imbalance of antioxidants and superoxide in favour of the latter causing damage to muscle tissue. This is known as oxidative stress.
So at this point you’re probably wondering why making a conscious effort to eat more foods that are high in antioxidants or even supplementing your diet with them is a bad thing.
Most of us train to see some improvement in our health, in our appearance or our running time. And most of us realise that we can’t progress without a little pain somewhere down the line. Waking up the next morning with aches and pains is usually a good indicator of an intense and beneficial workout.
No pain, no gain
Aching on a molecular level translates as injury to muscle fibres. As part of the recovery process the affected areas see an increase in white blood cell migration. Although this is a vital process in the regeneration of damaged muscle tissue these white blood cells release a significant amount of ROS. The effect of this release can be such that previously undamaged muscle tissue may also be affected.
This hints that ROS may play a role in the remodelling of muscle fibres, preparing them for future bouts of intense exercise. Supplementing your diet with antioxidants and subsequently reducing free radical activity may actually inhibit this process by removing the stimulus resulting in a delay in muscle adaptation.
Furthermore research conducted by Gomez-Cabrera investigated the effects of a powerful antioxidant called allopurinol on rats subjected to exercise. One group of rats were administered with allopurinol and exercised whilst the second group were just exercised.
In group 1 allopurinol neutralised almost all free radical and ROS activity, preventing the harmful side-effects. As expected, in group 2 free radical and ROS production increased. However they also witnessed increased activity of many proteins associated with muscle adaptation and up-regulation of superoxide dismutase, the body’s own natural antioxidant.
It seems that cells have sought to utilise free radicals and ROS in a controlled manner to signal adaptive responses. By ingesting too many antioxidants we might be disturbing our body’s natural homeostatic balance of antioxidants and free radicals. Why expend energy creating enzymes to breakdown muscle tissue for remodelling if something already exists within muscle that we can use?
Everything in Moderation
The most unscientifically scientific advice I can give to anyone, not just athletes, is a slightly clichéd phrase my mother has used since I was a young child. Everything in moderation.
While this does not quantify how much of something you should eat or drink or how often you should do so it does lend itself nicely to the antioxidant / free radical debate. By eating a healthy balanced diet our bodies receive all of the fuel and nutrients it needs to maintain itself and very often needs no form of supplementation.
Further research is being conducted to better understand these processes but the general consensus within the scientific community is shifting away from antioxidants being a miracle cure. In the media however they will continue to be held in high esteem until the next fad comes along.
 Gomez-Cabrera et al. (2005). http://onlinelibrary.wiley.com/doi/10.1113/jphysiol.2004.080564/pdf
 Jackson (2006). http://www.ncbi.nlm.nih.gov/pubmed/18191749
 Jackson (1999). http://journals.cambridge.org/download.php?file=%2F45433_C7E9F050E85211B6C5EC594C275AF200_journals__PNS_PNS58_03_S0029665199000877a.pdf&cover=Y&code=7d666d9b1b173358a239898b8d35813a