The effect of beta-carotene on race performance was evaluated using eleven well-trained runners (all running 40 miles per week) while monitoring the time to complete a 5 kilometer race by K. LeBanc, Ph.D. and coworkers from Louisiana State University, Baton Rouge, LA. In addition, beta-carotene's effects on oxidative stress was also measured by malondialdehyde (MDA) concentrations, a marker of muscle damage.

These subjects were tested using a double blinded, cross-over design. During the supplemental phase, each subject ingested 25000 IU of beta-carotene daily. The results indicated that there was a statistically significant improvement in 5 kilometer race performance. The average race times during the placebo and beta-carotene phases were 19:55 minutes and 19:18 minutes respectively. In addition, 64% of the subjects noted a subjective benefit from the use of beta-carotene supplementation. There was no statistically significant effect on MDA levels.

The results of this study indicate that beta-carotene can provide a beneficial influence on race performance in well-trained runners. 

Reference: Medicine and Science in Sports and Exercise. 31: S118, 1999.