The possible causes of zinc deficiency in athletes are inadequate intakes, excessive losses by sweat and urine, and redistribution of plasma zinc to specific tissues to counteract the oxidative stress and the maintenance of the immune response. Intense physical exercise increases oxygen consumption and induces excessive formation of free radicals and reactive oxygen species (ROS). ROS may promote lipid perioxidation, protein oxidation and cell damage.
In a recent study (2012), undertaken by Sao Paulo University, Brazil, elite swimmers were found to have plasma zinc concentrations below normal levels and erythrocyte zinc levels at borderline or within lower reference limits. Previous findings support this most recent study, with Lukaski et al., (1990), demonstrating a decrease in plasma zinc levels for competitive swimmers at the beginning, during, and post training. More recent findings (1992, 1995) reinforce the work of Lukaski et al., (1990), by showing low plasma zinc concentrations before, during and 30 minutes after training in elite swimmers, especially during rest periods after exercise.
In the most recent study (2012) athletes were evaluated at three different times: two time points being scheduled within 48 hours after training. It is thought, that the times selected may have influenced plasma zinc concentrations given that strenuous physical activity increases oxygen demand compared with resting conditions. It is well understood that increased mitochondrial oxygen consumption produces an oxidative stress that leads to the generation of reactive oxygen species and lipid perioxidation, resulting in muscle inflammation and damage. This being so, elite swimmers may be at increased risk of injury due to ongoing low plasma zinc concentrations.
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