Powering up performance-enhancing supplements: Should you combine beetroot with citrulline? Original paper

In this randomized crossover trial in elite rowers, supplementing with beetroot + citrulline had little effect on exercise performance metrics, compared to beetroot alone and to a placebo.

Whether supplementing with beetroot and citrulline is better than beetroot alone for improving exercise performance in athletes.

The outcomes assessed were countermovement jump height, VO₂peak, power output (average power and peak power), blood lactate (exercise), and maximum heart rate.

20 male elite rowers (average age of 29; average rowing experience of 13 years).

In this 7-day randomized crossover trial, the participants supplemented with either beetroot extract (BR; 3.5 grams, providing 500 milligrams of nitrate), beetroot extract and citrulline (BR+CIT; 3.5 grams and 6 grams, respectively), or a placebo every day.

At the end of each supplementation period, there was a study visit in which the participants performed a countermovement jump test, followed by a Wingate test (all-out rowing for 45 seconds), and finally, a VO₂peak test (the participants rowed against an incrementally increasing resistance until volitional exhaustion). Blood lactate was assessed before the Wingate test and 3 and 5 minutes after, peak power output was assessed during both the Wingate test and the VO₂peak test, and maximum heart rate was assessed during the VO₂peak test.

All of the participants completed the same weekly training regimen throughout the study, and they refrained from strenuous exercise for 24 hours before each test. A registered dietitian prescribed an individualized diet for each participant.

Compared to the placebo, peak power output during the VO₂peak test (but not the Wingate test) was higher with BR+CIT.

A potential limitation is that there was no washout period between conditions, so it’s possible that the residual effects of one supplementation period influenced the subsequent supplementation period.