Waltham International Symposium: Pet Nutrition Coming of Age Supplemental Vitamin C Appears to Slow Racing Greyhounds 1,2 Rebecca J. Marshall, Karen C. Scott, Richard C. Hill, 3 Daniel D. Lewis, Deborah Sundstrom, Galin L. Jones* and Jean Harper † Department of Small Animal Clinical Sciences and the Center for Veterinary Sports Medicine, College of Veterinary Medicine, University of Florida, Gainesville, FL; *School of Statistics, University of Minnesota, Minneapolis, MN and † Waltham Centre for Pet Nutrition, Leicestershire, UK ABSTRACT During strenuous exercise, markers of oxidation increase and antioxidant capacity decreases. Antioxidants such as vitamin C may combat this oxidation stress. The benefits of vitamin C to greyhounds undertaking intense sprint exercise has not been investigated. The objective of this experiment was to determine whether a large dose (1 g or 57 mmol) of ascorbic acid influences performance and oxidative stress in greyhounds. Five adult female, trained racing greyhounds were assigned to receive each of three treatments for 4 wk per treatment: 1) no supplemental ascorbate; 2) 1 g oral ascorbate daily, administered after racing; 3) 1 g oral ascorbate daily, administered 1 h before racing. Dogs raced 500 m twice weekly. At the end of each treatment period, blood was collected before and 5 min, 60 min and 24 h after racing. Plasma ascorbate, -tocopherol, thiobarbituric acid-reducing substances (TBARS) and Trolox equivalent antioxidant capacity (TEAC) concentrations were mea- sured and adjusted to compensate for hemoconcentration after racing. TBARS, TEAC and -tocopherol concen- trations were unaffected by supplemental vitamin C. Plasma ascorbic acid concentrations 60 min after racing were higher in dogs that received vitamin C before racing than in dogs that either received no vitamin C or received vitamin C after racing. The dogs ran, on average, 0.2 s slower when supplemented with 1 g of vitamin C, equivalent to a lead of 3 m at the finish of a 500-m race. Supplementation with vitamin C, therefore, appeared to slow racing greyhounds. J. Nutr. 132: 1616S–1621S, 2002. KEY WORDS: ● antioxidants ● vitamin C ● exercise ● dogs Free radicals and other reactive oxygen species (ROS 4 ) are produced during normal metabolism. These molecules are highly reactive with phospholipid membranes, triglycerides, nucleic acids, proteins and polysaccharides (1). Nutritive- reducing substances and scavenging enzymes inhibit ROS pro- duction and are normally present in sufficient quantities to prevent cell damage. During exercise, however, the production of ROS and markers of oxidation, such as malondialdehyde and TBARS, appears to increase in proportion to the severity of exercise, whereas antioxidant concentrations decrease (2,3). This oxidative stress has the potential to cause muscle damage, and several investigators have examined whether supplemental antioxidants limit exercise-induced oxidative muscle damage in human (4 –9), canine (10 –13) and equine (14,15) athletes. In sled dogs, plasma concentrations of isoprostane (a marker of lipid peroxidation) and creatine kinase (a marker of muscle damage) increase and vitamin E concentrations de- crease during strenuous endurance exercise (10). Supplemen- tation of sled dogs with -tocopheryl acetate, -carotene and lutein daily for 1 mo decreased DNA oxidation associated with endurance exercise and increased the resistance of lipoprotein particles to oxidation in vitro (11). Daily supplementation of vitamin E (457 IU), -carotene (5.1 mg) and vitamin C (706 mg) did not mitigate the increase in circulating creatine kinase concentrations associated with endurance exercise in sled dogs but there was a significant association between prerace vitamin E concentrations and completion of a race (12). Most studies, however, have failed to show an effect of antioxidant supple- mentation on performance (16). Previous experiments in this laboratory have shown that greyhounds run a consistent race from wk to wk and that dietary manipulation can affect performance (17,18). We have also found that serum vitamin E declines and oxidative stress increases after a short sprint race but that supplementation with high (1000 IU) but not moderate (100 IU) daily doses of 1 Presented as part of the Waltham International Symposium: Pet Nutrition Coming of Age held in Vancouver, Canada, August 6 –7, 2001. This symposium and the publication of symposium proceedings were sponsored by the Waltham Centre for Pet Nutrition. Guest editors for this supplement were James G. Morris, University of California, Davis, Ivan H. Burger, consultant to Mars UK Limited, Carl L. Keen, University of California, Davis, and D’Ann Finley, University of California, Davis. 2 Supported by the Waltham Centre for Pet Nutrition, Leicestershire, UK, and the University of Florida Center for Veterinary Sports Medicine, Gainesville, FL. 3 To whom correspondence should be addressed. E-mail: hillr@mail.vetmed.ufl.edu. 4 Abbreviations used: ALP, alkaline phosphatase; ALT, alanine transaminase; AST, aspartate transaminase; BUN, blood urea nitrogen; CPK, creatine phos- phokinase; ME, metabolizable energy; RBC, red blood cell; ROS, reactive oxygen species; TBARS, thiobarbituric acid-reducing substances; TEAC, Trolox equiva- lent antioxidant capacity; TDF, total dietary fiber; WBC, white blood cell. 0022-3166/02 $3.00 © 2002 American Society for Nutritional Sciences. 1616S Downloaded from https://academic.oup.com/jn/article-abstract/132/6/1616S/4687851 by guest on 23 May 2020