Antioxidants Beneficial if Not Overdone

Antioxidants like vitamins E and C are beneficial to exercising horses, but only at recommended levels, reported Carey Williams, PhD, equine extension specialist and associate director of the Rutgers University Equine Science Center. Williams presented this information in her talk titled "Antioxidant Research and Its Application to Feeding Horses" at the 2010 Kentucky Equine Research (KER) Nutrition Conference held April 26-27.

Oxidation is the biochemical process by which energy is created for cells to maintain both integrity and function. When not all of the oxygen is consumed during oxidation, damaging reactive oxygen species (ROS) are produced.

"These ROS damage DNA, lipids, and contribute to degenerative changes such as aging and cancer," said Williams. "Antioxidants may prevent damage by scavenging ROS, decreasing the conversion of less reactive ROS to more reactive ROS, assisting the repair of damage caused by ROS, and providing a favorable environment for other antioxidants."

The positive effects of both vitamin E and vitamin C in exercising horses have been reported in athletic horses.

"For example, horses supplemented with vitamin E had a more moderate degree of programmed cell death (apoptosis) in white blood cells, higher levels of other antioxidants in their systems like glutathione, and lower levels of the muscle enzyme creatine kinase, which can leak out of potentially damaged cells and into the blood if not protected," summarized Williams.

Williams' review of the literature on antioxidants also found that older horses also appear to have higher degrees of apoptosis in their white blood cells and may be able to reap the protective rewards of antioxidant supplementation, especially while exercising.

Williams did note, however, that caution should be taken when supplementing with high levels of vitamin E.

"Research studies conducted in my laboratory indicated that high levels of vitamin E (10 times the recommended 1000 UI/day) may be detrimental to the metabolism of beta-carotene, a precursor of vitamin A," Williams explained. "High levels of vitamin E should be avoided."

More information regarding the 17th KER nutrition conference, summaries of some presentations, and video interviews is available at

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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