Kevin Shimkus, B.S.
As important as regular physical exercise is for general health and well-being, a chronic lack of activity contributes to increased chances of adverse health risks and a decreased quality of life. Paradoxically, both of these opposing situations (as well as several others) are associated with an increased production of reactive oxygen species (ROS), commonly known as oxidants or free radicals. ROS are produced in the body and are highly reactive molecules that ‘steal’ electrons from fats, proteins, DNA, and other nearby molecules, who can then ‘steal’ from another molecule, creating a chain-reaction of energy transfers that can damage a cell. These reactions, to a limited extent occur constantly and almost instantly, and can be very dangerous to cells when in high concentrations. With this knowledge, general recommendations for the past 20-30 years have encouraged individuals to increase the body’s concentration of antioxidants- molecules known to buffer and reduce the effects of ROS, to best prevent the damaging effects of free radicals in the body. Since exercise increases ROS production, athletes are one of the populations most susceptible for high levels of damage. However, antioxidants such as vitamins C and E are readily available and cost-effective supplements, allowing nutrition-conscientious athletes the possibility of maintaining high concentrations of antioxidant levels in their bodies. Focusing on muscle, this article aims to point out how new research may identify the importance of ROS signaling during and after exercise and how typical athletes may actually hinder their own gains through over-supplementation of antioxidants.
ROS production can occur within several areas of the muscle cell, including the mitochondria (which produce the cell’s energy) and contractile proteins (the structure that allows muscle to move). Physical activity increases metabolic reactions at each of these sites and contributes to elevated creation of free radicals which can travel, react, and damage all structures of the muscle cell. Antioxidant deficiencies and chronically elevated ROS concentrations can contribute to muscle loss and diminished function through many mechanisms, including protein breakdown, mitochondrial deficiencies, and cell death. Many studies have shown that muscle loss due to inactivity can be delayed or reduced by antioxidant supplementation. But the magnitude and duration of ROS exposure during and immediately following physical activity is actually helpful for signaling the cell to improve due to exercise training, and an overabundance of ingested supplements can reduce exercise’s effects.
A 2008 study looked at the effects of vitamin C (1g/day, a dosage commonly used by sport practitioners) on eight weeks of cycling training changes in men and found that those taking vitamin C supplements at this dosage had decreased endurance capacity and metabolic adaptations compared to the non-supplemented group. Strength athletes may hurt their gains as well, as protein rebuilding and sensitivity to insulin (a muscle-building hormone) are affected by ROS and could theoretically be slowed by an overabundance of antioxidants. Athletes actually have naturally improved antioxidant capacities following training and are better able to handle the increased exposure to free radicals, and a well-varied diet might help provide additional antioxidants to keep the individual at the optimum range, independent of supplementation.
While not yet fully understood, research continues to explain how activity-induced ROS levels create a different response than those seen during injury or inactivity. And while not dismissing the importance of antioxidants and the needs of certain populations to heavily supplement to combat ROS, athletes with moderate levels of antioxidant concentrations should consult educated professionals to optimize their nutrition not only their general health but for also maximizing training gains.
Articles to consider:
- Powers, S. K., Duarte, J., Kavazis, A. N. and Talbert, E. E. (2010). “Reactive oxygen species are signalling molecules for skeletal muscle adaptation.” Experimental Physiology 95: 1–9. http://ep.physoc.org/content/95/1/1.full.pdf+html
- Gomez-Cabrera, M.-C., E. Domenech, et al. (2008). "Oral administration of vitamin C decreases muscle mitochondrial biogenesis and hampers training-induced adaptations in endurance performance." The American Journal of Clinical Nutrition 87(1): 142-149. http://ajcn.nutrition.org/content/87/1/142.full.pdf+html