Free radicals have traditionally received a negative press. These highly reactive molecules, produced naturally in the body, can damage cells and are thought to contribute to, among other things, the development of cancer. They sound pretty nasty then and, as exercise increases their production, many athletes try to counter the effects of free radicals by dosing up with the supposed antidote – antioxidant vitamins. But before you drop another E (vitamin), could it be time to go supplement cold turkey?
Super supplements containing ‘good’ antioxidant vitamins such as A, C, E and selenium are flying off the shelves. Perhaps this isn’t surprising, considering that research, such as that carried out by Elodie Gauche and her team from the National Institute of Sport and Physical Education in France, suggests these mixtures can aid recovery from hard exercise, and offset the cell and muscle damage caused by the free radicals produced during training and racing.
Certainly many athletes seem to be taking these studies seriously. The 2005 UK Sport Drug Free Survey of 520 athletes found 70 per cent used vitamin C supplements. Similarly, in a study of 1,620 elite athletes, Jorunn Sundgot-Borgen at the Norwegian School of Sports Science found that over a quarter of males and more than 40 per cent of females took mineral supplements. Not a problem, you might think, but if these athletes are habitually ‘mega-dosing’ – excessively exceeding the recommended daily intake (RDA) for the vitamins – they could, at the very least, be harming their performance and, worse, they could possibly be harming their overall health.
Less is more
When it comes to performance on your bike, highly respected IndianaUniversity researchers Jaume Padilla and Tim Mickleborough have suggested that antioxidants may prevent favourable adaptations to training. They cite research on athletes competing in ultra endurance events who showed significant increases in oxidative stress – the amount of damage within the muscle caused by racing – when taking around 1000mg of vitamin C daily – over 16 times the UK RDA of 60mg – for around five years compared to those not using supplements.
In their letter to the Journal of Medicine in Science and Exercise, the two experts concluded: “We believe that the recommendation that physically active individuals should supplement with antioxidants needs to be revised as exogenous [outside sources of] antioxidants may prevent useful and protective adaptations to habitual exercise.”
In other words, overdoing antioxidants may be giving you fewer fitness gains for the time that you put in – it could even be causing a hole in the defences against future exercise stress. This was echoed by several leading experts at the PowerBar Sports Nutrition Conference in the summer of 2007, who suggested that high doses of antioxidants may actually be reducing the training gains of athletes.
This isn’t just a couple of boffins trying to rock the establishment boat. Other researchers have also suggested that raised levels of free radicals do not automatically mean that all that is happening is bad. In fact, free radicals ‘signal’ other pathways to make useful adaptations; they are a part of the metabolism of oxygen and therefore a pathway of communication to other processes in the body. Part of the adaptation to exercise is to make the body’s capacity to withstand the stress of raised oxygen use more effective for future events. You not only get fitter through training, your body also gets better at dealing with the waste products that result from exercise. This is a beneficial adaptation for the body in order to tolerate future exposure to exercise stress, a process termed hormesis. If the free radicals do not get to signal processes that should take place after training stress, fewer training benefits result – which could explain why antioxidant over-dosing results in some amateur athletes piling in mileage but failing to show the results in races.
While some believe that free radicals cause ageing, cancer and diseases such as Parkinson’s, others claim that they may actually extend life. Research on cells shows that free radicals produced from oxygen use cause an extension of the cell life as a result, and questions the use of antioxidants in some diseases such as diabetes, while a study in the Journal of the American Medical Association by Goran Bjelakovic from Copenhagen University Hospital, Denmark, published in early 2007, analysing data on 180,000 human subjects, found that antioxidant supplements beta carotene, A and E may ‘increase mortality’.
Free radicals may be linked to certain degenerative processes, but they also form part of the adaptation to stress that your body is under every day. They are doing a job that does not need to be totally quelled and, paradoxically, the common response of mega dosing with antioxidants is not good for you or your performance gains. Instead, eat a wide variety of colourful fruit and vegetables: fruit and veg packed with natural antioxidants like tomatoes, carrots, spinach, raisins, oranges, berries, grapes, kiwi, kale, broccoli and red peppers – giving some well-needed variety from the boring apple or banana option that most people stick to.
Recommended daily allowance of antioxidants
To give you an idea of the values for normal dietary intake, current RDA mean values for antioxidants across seven countries in the EU are:
- Vitamin A (800-2400ug [microgram])
- Vitamin C (60-180mg),
- Vitamin E (10-20mg)
- Selenium (55-88ug)