The Lowdown on L-Citrulline for Peak Performance
by Meg Smith
This week’s newsletter looks at the effects of L-citrulline as a pre-workout supplement, based on a study conducted by Coach Meg as part of her university studies.
Have you ever wondered what’s behind all the hype about L-citrulline in your pre-workout supplement? It’s promoted as a performance enhancer, claiming to pump more blood to your muscles for better workouts (1). But before you measure out another scoop, let’s take a closer look at the science behind L-citrulline to see if these claims are the real deal, or just another marketing ploy from big nutrition brands.
The science behind L-citrulline
After you consume L-citrulline, it makes its way to your kidneys, where it gets converted to L-arginine, a necessary process for the production of nitric oxide (2). Nitric oxide plays a crucial role in enhancing exercise performance as it increases blood flow by widening your blood vessels, allowing more blood containing oxygen and nutrients to be delivered to your working muscles during exercise (2). This increased blood flow also means that waste products, which are produced by the muscles during exercise (such as lactic acid), are removed from circulation quicker, improving muscle function and aiding in the recovery process (3). Now that you’ve got a basic understanding of the science behind L-citrulline, let’s explore its various forms and their distinct benefits.
Types of Citrulline Supplementation
Citrulline is commonly found in pre-workout supplementation products and comes in 2 common forms: L-citrulline and citrulline malate. Both forms have been found to enhance performance, but in different ways.
Citrulline Malate: a combination of L-citrulline and malic acid. Usually, 6g citrulline + 2g malate. Citrulline malate works to replenish the muscles’ energy store more rapidly, leading to quicker recovery and boosting strength and power performances (4). It has also been shown to increase the number of reps performed in upper and lower body weighted exercises, reduce fatigue, and help lessen muscle soreness after exercise (5).
L-Citrulline: an amino acid found in watermelon and produced naturally by the body (2). Also typically found in pre-workout supplementation, usually in 6g doses. L-citrulline directly converts to L-arginine in the body, leading to increased nitric oxide production and improved exercise performance (2). Less is understood about the potential performance benefits of pure L-citrulline and whether it could outweigh the benefits of citrulline malate. This is where our study steps in, aiming to uncover whether L-citrulline holds the key to unlocking those performance PBs.
Study Details
To understand the effect of pure L-citrulline on performance, we carried out a simple experiment. Young, healthy, and active participants volunteered to take part in this experiment where they were required to perform 2 performance tests consisting of 3 exercises, separated by 7 days (details below). The participants were either given a sugar pill (a pill that looked the same as the L-citrulline supplement but didn't contain any active ingredients) or a 6g dose of L-citrulline. The participants were unaware which pill they had been given to see if the effects observed (if any at all) were caused by the actual supplement or simply the participant's perception of its effectiveness.
Study Design
Study Results
The results show that L-citrulline supplementation provided no performance improvements for the number of press ups and Counter Movement Jump (CMJ) height achieved. Hand grip strength decreased with L-citrulline supplementation. There was no difference between males and females observed. Now that we've seen the study outcomes, let's explore what these results mean and consider some important factors to keep in mind when deciding what pre-workout mix to load up on!
Thoughts on L-citrulline: Exploring Options and Factors to Consider
After reviewing our experiment's findings, it's important to think about what might have affected the results and suggest what your best options moving forwards may be.
Individual Differences Matter: In our study, there were no effects on 2 of our performance tests, however, L-citrulline had a negative effect on hand grip strength. 16 out of our 26 participants produced a lower score on the hand grip strength dynamometer after they had L-citrulline supplementation, with the remaining 10 seeing no differences or some even improvements with L-citrulline supplementation. Another study found that taking L-citrulline reduced time to exhaustion on a graded treadmill test.6 This highlights that everyone’s body responds differently to supplementation and therefore results may vary between individuals. Therefore, even though 2 of our performance tests were unaffected by L-citrulline supplementation, the reduction in hand grip strength suggests that L-citrulline does have the potential to negatively impact performance. We would suggest that pre-workout supplementation containing citrulline malate is the way to go.
Exercise Variation: We used simple bodyweight exercises; press ups and CMJs in our experiment. These exercises might not capture all the challenges you face during a regular gym workout. Research using heavier weights, up to 80% of one-repetition maximum lift, has shown performance improvements with L-citrulline and citrulline malate (5). This could suggest that citrulline supplements have greater potential to enhance strength and power performance when working closer to maximum.
Short-Term vs. Long-Term Effects: Our study only looked at the immediate effects of taking 6g of L-citrulline 60 minutes before exercise. However, other research showing performance improvements used longer-term supplementation, up to 8 days, and hence, current L-citrulline supplementation recommendations suggest taking the supplement every day for about a week makes it more likely to see good results (2).
Choosing Wisely: Optimal Supplements for Your Gym Journey
After looking at our study's results, it's clear that L-citrulline didn't boost performance as expected. It actually made hand grip strength worse for many. It seems everyone's body responds differently to supplements, but to hit those PBs in the gym, citrulline malate seems like a safer bet. It's essential to think about how hard you're exercising, how long you're taking the supplement, and that everyone's different when it comes to supplements. We would recommend citrulline malate as your go to pre-workout but remember that no supplement should ever replace a healthy diet and lifestyle. Always prioritise your overall health and consult with a healthcare professional before starting any new supplement regime.
References:
1. Bailey SJ, Blackwell JR, Lord T, Vanhatalo A, Winyard PG, Jones AM. l-Citrulline supplementation improves O2 uptake kinetics and high-intensity exercise performance in humans. Journal of Applied Physiology. 2015;119(4):385-395. doi:https://doi.org/10.1152/japplphysiol.00192.2014
2. Gonzalez AM, Trexler ET. Effects of Citrulline Supplementation on Exercise Performance in Humans. Journal of Strength and Conditioning Research. 2020;34(5):1. doi:https://doi.org/10.1519/jsc.0000000000003426
3. Bescós R, Sureda A, Tur JA, Pons A. The effect of nitric-oxide-related supplements on human performance. Sports medicine (Auckland, NZ). 2012;42(2):99-117. doi:https://doi.org/10.2165/11596860-000000000-00000
4. Gough LA, Sparks SA, McNaughton LR, et al. A critical review of citrulline malate supplementation and exercise performance. European Journal of Applied Physiology. 2021;121(12). doi:https://doi.org/10.1007/s00421-021-04774-6
5. Glenn JM, Gray M, Wethington LN, Stone MS, Stewart RW, Moyen NE. Acute citrulline malate supplementation improves upper- and lower-body submaximal weightlifting exercise performance in resistance-trained females. European Journal of Nutrition. 2015;56(2):775-784. doi:https://doi.org/10.1007/s00394-015-1124-6
6. Hickner RC, Tanner CJ, Evans CA, et al. L-Citrulline Reduces Time to Exhaustion and Insulin Response to a Graded Exercise Test. Medicine & Science in Sports & Exercise. 2006;38(4):660-666. doi:https://doi.org/10.1249/01.mss.0000210197.02576.da