If you dive into the ingredient list of any half decent pre-workout supplement, there are going to be some key ingredients that you should expect to see -- with citrulline and beta-alanine being two of them.
These two compounds are amongst some of the most well-researched supplements in the health industry, with a number of individual studies supporting their use.
But the question remains -- is one better than the other, or do you need them both?
What is Citrulline?
Citrulline is a specific type of amino acid found in the human body. Interestingly, it is also found naturally occurring in a variety of fruits and vegetables, including watermelon, squash, cucumber, pumpkin, rockmelon, and honeydew melon.
As an amino acid, citrulline is considered to be “non-essential” because your body does not have the capacity to produce any of its own.
However, it is important to note that your body's ability to create citrulline molecules is not infinite.
In fact, this production process is predicated on having adequate nutrients available to facilitate it. With this in mind, there is a growing body of evidence to suggest that supplementing with greater amounts of citrulline can offer a number of unique benefits.
See, citrulline plays a number of different roles in the human body.
Most people know citrulline for the role it plays in the “urea cycle”, which is the process by which your body eliminates harmful compounds. As such, citrulline is an important part of keeping your body healthy and toxin free.
More importantly, citrulline acts as a “vasodilator”, which is a fancy way of saying it widens your blood vessels. As a result, its supplementation can increase blood flow to the muscle tissue, where it is believed to drive many of its benefits.
What is Beta-alanine?
Like citrulline, beta-alanine is also a specific amino acid that is found in your body, although this one is more predominantly found in your muscles and brain. Under normal conditions, beta-alanine combines with another amino acid called “histidine” to form a compound called “carnosine”.
It is actually for this specific reason that beta-alanine appears in so many pre-workout supplements. You see, carnosine helps reduce the accumulation of lactic acid in your muscle tissue during exercise, which staves off fatigue.
However, the amount of beta-alanine stored in your muscle tissue is relatively small compared to the amount of histidine. This ultimately impairs your ability to produce carnosine, inhibiting your ability to buffer lactic acid during exercise.
Consequently, supplementing with beta-alanine can cause an immediate increase in carnosine production, which has some very specific effects with respect to exercise and training.
Citrulline VS Beta-alanine: what are the benefits?
I have already outlined the role that both of these important compounds play in the human body.
Moreover, I have also alluded to the fact that because of the roles they play, their supplementation can have some pretty significant benefits -- and here they are.
Benefits of Citrulline
I have already mentioned that citrulline is a vasodilator -- which means it helps relax and widen your blood vessels. This is particularly important, because citrulline increases blood flow to your muscle tissue, enhancing the delivery of oxygen and nutrients.
With this in mind, a number of studies have clearly shown that citrulline supplementation can improve weight training performance by increasing the number of repetitions you can perform at a given workload .
For example, without taking citrulline you might be able to bench press three sets of ten reps at 80kgs. Then, with the addition of a citrulline supplement, you might be able to perform three sets of twelve reps using 80kgs.
In the short term this is obviously pretty cool -- but the long term benefits are really what are important here.
If you increase the number of reps you perform in your training session, you see a subsequent increase in your total training volume. Over the duration of a training block this can lead to marked improvements in muscle growth and muscle strength.
Which is precisely why it is such a useful supplement.
As an added bonus, the improved blood flow that comes with citrulline supplementation will also improve your recovery after exercise .
By promoting the movement of proteins and nutrients into your muscle tissue after training, citrulline ensures that your muscles have everything they need to repair and grow stronger. This speeds up recovery between sessions, while also lowering muscle soreness after your session.
Again, the thing to consider here is that improved recovery between training sessions maximises the quality of your subsequent training sessions -- which can again contribute to substantial improvements in strength and size over a longer term training block.
Talk about some serious benefits.
The Benefits of Beta-alanine
As I have already outlined in detail, beta-alanine works in a very different manner to citrulline, where it increases the production of carnosine within your muscle tissue -- which directly limits the build up of lactic acid during exercise.
This ultimately leads to better fatigue resistance when you train.
As a result, the supplementation of beta-alanine has been shown to improve muscular and aerobic endurance during training. This also appears to help you feel less fatigued during your training session, which is quite important .
Collectively this leads to similar results as citrulline, where the amount of repetitions you can perform at a given workload increases. Moreover, as beta-alanine will limit the amount you fatigue across the duration of a training session, it also ensures that every single set you perform is of a high quality.
Over time this can contribute to further increases in volume, promoting additional muscle growth.
Interestingly, the supplementation of beta-alanine has also been shown to enhance fat loss significantly over the duration of a training program, which most likely comes down to your ability to work harder for longer .
This makes it a great option for people in either a bulking OR cutting phase of training.
And the winner is…
Citrulline -- but only by a very small margin.
Both citrulline and beta-alanine have a profound effect on exercise performance by increasing your ability to resist fatigue during your workout. This causes a substantial increase in training volume, which can lead to improvements in muscle size and strength.
And even though beta-alanine appears to help accelerate fat loss, the fact that citrulline also improves recovery after exercise gives it a very slight edge.
With that in mind, if you had to choose one of the two, then citrulline is probably going to offer you a little more bang for your buck.
Now, do you want to hear some good news?
You don't have to choose one!
One thing that I have not yet addressed is the fact that citrulline and beta-alanine appear to improve performance through two very distinct mechanisms. This means that their supplementation is going to be complimentary, rather than having one detract from the other.
As a result, taking both of them pre-workout is likely going to be more beneficial than having one alone.
I guess there is a very good reason that most high-quality pre-workout supplements include both of these compounds within their formula -- because they both work extremely well.
Citrulline and beta-alanine are two of the most commonly used pre-workout compounds on the market -- and for very good reason too. They both have the ability to improve gym performance, reduce fatigue, and accelerate increases in muscle size and strength.
Moreover, with benefits for fat loss and recovery, they both deserve a place in your supplement regime.
- Gonzalez, Adam M., and Eric T. Trexler. "Effects of citrulline supplementation on exercise performance in humans: A review of the current literature." The Journal of Strength & Conditioning Research 34.5 (2020): 1480-1495.
- Sureda, Antoni, and Antoni Pons. "Arginine and citrulline supplementation in sports and exercise: ergogenic nutrients?." Acute topics in sport nutrition 59 (2012): 18-28.
- Hobson, R. M., Saunders, B., Ball, G., Harris, R. C., & Sale, C. (2012). Effects of ?-alanine supplementation on exercise performance: a meta-analysis. Amino acids, 43(1), 25-37.
- Kern, B. D., & Robinson, T. L. (2011). Effects of ?-alanine supplementation on performance and body composition in collegiate wrestlers and football players. The Journal of Strength & Conditioning Research, 25(7), 1804-1815.