Glutathione in Athletic Performance, Endurance, and Sports Nutrition
Physical exercise intensity can be related to plasma glutathione levels
Gambelunghe C, Rossi R, Micheletti A, Mariucci G, Rufini S. [J Physiol Biochem 2001 Mar;57(2):9-14] The aim of the present study was to examine the effect of different kinds of physical exercise on plasma glutathione levels. Our results suggest that GSH plays a central antioxidant role in blood during intensive physical exercise and that its modifications are closely related to exercise intensity.
Oxidants, antioxidant nutrients and the athlete
Packer L. [Department of Molecular and Cell Biology, University of California, Berkeley 94720-3200, USA.] Strenuous physical exercise induces oxidative stress. Severe or prolonged exercise can overwhelm antioxidant defences, which include vitamins E and C and thiol antioxidants, which are interlinked in an antioxidant network, as well as antioxidant enzymes. Evidence for oxidative stress and damage during exercise comes from direct measurement of free radicals, from measurement of damage to lipids and DNA, and from measurement of antioxidant redox status, especially glutathione. There is little evidence that antioxidant supplementation can improve performance, but a large body of work suggests that bolstering antioxidant defences may ameliorate exercise-induced damage, suggesting that the benefits of antioxidant intervention may be for the long term rather than the short term.
Antioxidants and physical performance
Clarkson PM. Department of Exercise Science, University of Massachusetts, Amherst 01003, USA.[Crit Rev Food Sci Nutr 1995 Jan;35(1-2):131-41] Performance of strenuous physical activity can increase oxygen consumption by 10- to 15-fold over rest to meet energy demands. The resulting elevated oxygen consumption produces an “oxidative stress” that leads to the generation of free radicals and lipid peroxidation. A defense system of free radical scavengers minimizes these dangerous radicals. Changes in antioxidant scavengers and associated enzymes (e.g., glutathione, tocopherol, glutathione peroxidase) also provide clues about demands on the defense system. Physical training has been shown to result in an augmented antioxidant system and a reduction in lipid peroxidation. Supplementation with antioxidants appears to reduce lipid peroxidation but has not been shown to enhance exercise performance. The “weekend athlete” may not have the augmented antioxidant defense system produced through continued training. This may make them more susceptible to oxidative stress. Whether athletes or recreational exercisers should take antioxidant supplements remains controversial. However, it is important that those who exercise regularly or occasionally ingest foods rich in antioxidants.
Zamora AJ, Tessier F, Marconnet P, Margaritis I, Marini JF. [Eur J Appl Physiol 1995;71(6):505-11] The functional and structural responses to acute exercise (E) and training, (T) with or without selenium supplementation (Sel), were investigated in a double-blind study on 24 young male subjects. The results in Sel would seem to suggest a dampening effect of the selenium on the mitochondria changes, both in chronic and acute exercise. The mechanism of this action on mitochondrial turnover is uncertain, but might be related to a higher efficiency of the selenium-dependent enzyme glutathione peroxidase.
Reductions in blood glutamine concentration following intense exercise may contribute to immune suppression in overtrained athletes
- Plasma amino acid concentrations in the overtraining syndrome: Possible effects on the immune system
Parry-Billings M, Budgett R, Koutedakis K et al (1992). [Medicine and Science in Sports and Exercise 24, 1353-8] Overtraining and long-term exercise are associated with an impairment of immune function. We provide evidence in support of the hypothesis that the supply of glutamine, a key fuel for cells of the immune system, is impaired in these conditions and that this may contribute to immunosuppression. Plasma glutamine concentration was decreased in overtrained athletes and after long-term exercise (marathon race) and was increased after short-term, high intensity exercise (sprinting). Branched chain amino acid supplementation during long-term exercise was shown to prevent this decrease in the plasma glutamine level. Given the proposed importance of glutamine for cells of the immune system, it is concluded that the decrease in plasma glutamine concentration in overtraining and following long-term exercise, and not an intrinsic defect in T lymphocyte function, may contribute to the immune deficiency reported in these conditions.
- Immunological hazards from nutritional imbalance in athletes
Shephard RJ, Shek PN. [Exerc Immunol Rev 1998;4:22-48] This review examines the influences of nutritional imbalance on immune function of competitive athletes, who may adopt an unusual diet in an attempt to enhance performance. Since endurance exercise leads to protein catabolism, an athlete may need 2.0 g/kg protein rather than the 0.7-1.0 g/kg recommended for a sedentary individual. Both sustained exercise and overtraining reduce plasma glutamine levels, which may contribute to suppressed immune function postexercise. Vitamins are important to immune function because of their antioxidant role. However, the clinical benefits of vitamin C supplementation are not enhanced by the use of more complex vitamin mixtures, and excessive vitamin E can have negative effects. Iron, selenium, zinc, calcium, and magnesium ion all influence immune function. Supplements may be required after heavy sweating, but an excessive intake of iron facilitates bacterial growth.
- Glutamine, exercise and immune function. Links and possible mechanisms
Walsh NP, Blannin AK, Robson PJ, Gleeson M. [Sports Med 1998 Sep;26(3):177-91] Glutamine is the most abundant free amino acid in human muscle and plasma and is utilised at high rates by rapidly dividing cells, including leucocytes, to provide energy and optimal conditions for nucleotide biosynthesis. Falls in the plasma glutamine level have been reported following endurance events and prolonged exercise. These levels remain unchanged or temporarily elevated after short term, high intensity exercise. Plasma glutamine has also been reported to fall in patients with untreated diabetes mellitus, in diet-induced metabolic acidosis and in the recovery period following high intensity intermittent exercise. Furthermore, athletes experiencing discomfort from the overtraining syndrome exhibit lower resting levels of plasma glutamine than active healthy controls. Therefore, physical activity directly affects the availability of glutamine to the leucocytes and thus may influence immune function.
- Does endurance exercise impair glutamine metabolism?
Parry-Billings M, Blomstrand E, Leighton B et al (1990). Canadian Journal of Sport Science 13, 13P (abstract)
- Plasma glutamine changes after high intensity exercise in elite male swimmers. Kargotich S, Rowbottom DG, Keast D et al (1996). Medicine and Science in Sport and Exercise 28, S133 (abstract)