The term free radicals refers to substances that bring about cell damage, ageing, and even cancers. As you know, antioxidants are defense mechanisms against these deleterious events. Free radical production is known to be greater during exercise; hence, supplementation with these antioxidants. However, scientists are starting to discover this could be erroneous, and that for normal physiological functioning in the cells, there needs to be a balance between the free radicals and antioxidants.
Free radicals refer to reactive oxygen species (ROS) and nitrogen species (RNS). These are highly reactive in the body due to an unpaired valence electron (remember drawing your dots around your periodic elements in chemistry class?). The following are the five main radicals found in muscle fibers:
- Superoxide - formed in the mitochondria and cytosol
- Hydrogen peroxide - can be formed from superoxide via an enzyme.
- Hydroxl radical - which is formed when the previous two radicals react with metal ions such as iron or copper.
- Nitric Oxide (still want to take those pre-workout “pump” supplements?) - formed by the amino acid L-arginine reacting with the enzyme nitric oxide synthase
- Peroxy nitrite - formed in the cytosol when Superoxide reacts with Nitric Oxide
These are all linked with the mitochondrial transport chain activity (responsible for creating ATP for energy) and this is the primary reason they increase during exercise. When created, they wreak havoc on cell membranes, proteins, DNA, and even the ability of the muscle to contract (this one is due to Nitric Oxide. Like I said, do you still want to take your BSN NO-Xplode?)
Although you may think these are your enemies, scientists are starting to suggest that these radicals are necessary for proper exercise adaptations responsible for mitochondrial genesis and capillarization, muscle atrophy, glucose transport ability, increase in blood flow, and the cellular repair processes.
Antioxidants scavenge these free radicals and convert them into unreactive substances. They contain two classes: endogenous and exogenous (those that are consumed ie. Vitamins A, C, E). So let’s get to the negative effects of supplementing with antioxidants:
- One group reported significantly greater oxidative damage following half and full Ironman triathalons in athletes who took antioxidants suppelements than in those who did not.
- Other groups report interference of oral antioxidant vitamin C on exercise-induced signalling and dependent events such as the expression of an enzyme responsible for mitochondrial volume as well as improvements in insulin sensitivity.
- Another group reports that supplementing with vitamin C & E prevented exercise-induced vasodilation by blocking nitric oxide release (okay, maybe you do want to take your “pump” supplement).
- Mean improvements in oxygen uptake was 2 times greater and improvements in endurance capacity 7 times greater in humans who received a placebo rather than vitamin C daily via increases in peripheral adaptations to exercise.
- Vitamins E & C also have negative effects on muscle recovery from eccentric weight training by delaying the recovery process.
The authors conclude that more research is necessary to better understand dosage, timing, and settings necessary for antioxidant supplementation. Clearly, there needs to be a balance between free radicals and antioxidants. Now, free radicals are not so bad as you thought, n’est-ce pas (that’s French)?
Michah Gross, Oliver Baum & Hans Hoppeler (2011): European Journal of Sport Science, 11:1, 27-32