Oral vitamin E supplementation on oxidative stress, vitamin and antioxidant status in intensely exercised horses
Authors: WILLIAMS C. A., CARLUCCI S. A.
Journal: Equine Veterinary Journal
Summary
Williams and Carlucci investigated whether increasing vitamin E supplementation beyond standard recommendations could improve antioxidant status and reduce oxidative stress in exercising horses, given the lack of clear guidance on optimal dosing for athletic animals. Using a Latin square design, twelve unfit Standardbreds received either no supplementation (control), 5,000 IU/day, or 10,000 IU/day of DL-α-tocopheryl acetate across three four-week periods separated by washout phases, with blood sampling and heart rate monitoring during and after treadmill interval exercise tests. Notably, horses receiving vitamin E supplementation actually demonstrated higher heart rates during exercise compared to controls, whilst the high-dose group (10,000 IU/day) showed significantly lower plasma β-carotene levels than the moderate-dose group, suggesting potential metabolic interference between vitamin E and carotenoid absorption. Neither supplementation level reduced oxidative stress markers or improved antioxidant recovery compared to unsupplemented controls, despite the high-dose group receiving nearly ten times the 1989 NRC recommended allowance. For equine professionals managing intensely exercised horses, these findings suggest that excessive vitamin E supplementation offers no performance or metabolic advantage and may actually compromise micronutrient status; practitioners should reconsider blanket high-dose supplementation protocols and instead focus on meeting baseline requirements through balanced nutrition.
Read the full abstract on the publisher's site
Practical Takeaways
- •Supplementing intensely exercised horses with high-dose vitamin E (5,000-10,000 IU/day) does not improve their ability to handle oxidative stress or enhance recovery—save money by avoiding excessive supplementation above NRC recommendations
- •High-dose vitamin E may interfere with β-carotene metabolism; if supplementing, use moderate levels and monitor whether horses have adequate forage-based carotenoid intake
- •Horses' natural antioxidant systems respond adequately to intense exercise without supplementation; focus on consistent training, recovery time, and overall nutrition rather than megadose micronutrient protocols
Key Findings
- •Horses supplemented with 5,000 or 10,000 IU/day vitamin E showed no reduction in oxidative stress compared to unsupplemented controls during intense exercise
- •High-dose vitamin E (10,000 IU/day) resulted in significantly lower plasma β-carotene levels compared to moderate supplementation (5,000 IU/day), suggesting inhibitory effects on carotenoid metabolism
- •All groups showed exercise-induced increases in antioxidant markers (glutathione peroxidase, retinol, α-tocopherol) that returned to baseline within 24 hours regardless of supplementation level
- •Excessive vitamin E supplementation at 10-times the NRC recommended level provided no performance or metabolic advantage and may be counterproductive