Taking a pre-workout supplement has become more popular in recent years among everyone from weightlifters to cyclists and more. For those focused on lifting heavier weights and building muscle, or those hoping to give their aerobic exercises a little extra oomph, increasing your intake of the amino acid citrulline — a popular ingredient in supplements –– may be a good option.
The body produces citrulline naturally, and it’s available in certain foods. Citrulline supplements are an option as well, and gym-goers are taking note because, in addition to the role citrulline plays in removing ammonia from the body, it can also benefit exercisers. It widens blood vessels, which allows the flow of more blood to deliver oxygen and nutrients to the tissues when needed most during intense exercise. According to a systematic review and meta-analysis in the International Journal of Sport Nutrition and Exercise Metabolism, that effect can lead to “a small but potentially meaningful ergogenic performance effect during resistance exercise.”In other words, the research suggests citrulline supplements may give you a bit of a boost in your strength training session.
If you’d like to learn more about exactly how citrulline works in the body, what research says about it, and how much you may want to take before your next workout, you’ll find the following information useful.
What Does Citrulline Do?
Citrulline’s traditional job has to do with its role in the urea cycle, which removes ammonia from the body. But that function may not be of much interest for folks with a focus on fitness.
When it comes to taking citrulline supplements for workouts, the real appeal is citrulline’s ability to dilate blood vessels (also known as vasodilation) by increasing L-arginine bioavailability, thus promoting nitric oxide production.Basically, the true goal is to boost nitric oxide production, but supplements don’t contain solely nitric oxide; rather, they have substances that help your body produce it — substances like citrulline and arginine.
And that’s where things get interesting.
Studies have shown that, compared with just L-arginine supplementation, taking citrulline orally is a more efficient way to elevate plasma L-arginine concentrations in the body because the gut absorbs more citrulline than arginine, which, as previously mentioned, boosts nitric oxide production. And, since nitric oxide plays such an important role in the regulation of skeletal muscle and blood vessels, helping arteries relax and improving blood flow (potentially providing more oxygen and nutrients to the tissues, which may help us go harder in the gym), it’s easy to see why someone looking for bigger gains would be interested in upping their citrulline intake.
Additionally, even though citrulline is unlike some other amino acids in that it’s not used specifically to build proteins, studies have shown that it still influences protein synthesis, which may benefit the building of muscle.No wonder lifters are heading for the citrulline aisle, right?
While supplements are an easy way to increase your citrulline intake — and we’ll share more on the citrulline supplements available shortly — food sources are also on option.
Food Sources of Citrulline
Watermelon, including watermelon juice, is the food most frequently discussed regarding citrulline due to the fruit’s high citrulline concentration — a single cup of diced seedless watermelon contains 365 mg of citrulline.The Crimson Sweet watermelon and the Dixielee watermelon have been shown to have the highest levels.However, supplements may be a better option because you would need to eat between 2.2 and 3.3 pounds of fresh watermelon per day to get the minimum effective dose of citrulline, which is 3 grams per day.
Citrulline can be found in most other fruits, vegetables, and nuts too, although the levels researchers found in these other foods were considerably lower than in watermelon.It’s worth noting, though, that there hasn’t been a ton of research on food sources of citrulline, so researchers have yet to determine the exact content in many foods.
Different Types of Citrulline
When it comes to citrulline supplements, it’s important to note that there are two main forms: L-citrulline, which refers to citrulline on its own, and citrulline malate, which is citrulline combined with malic acid. The difference between the two options is a point of debate among some researchers.
While some research has been done on the positive effects of L-citrulline on exercise performance, citrulline malate is a newer and increasingly popular option in sports supplements.With this combination, determining which benefits should be attributed to citrulline and which are due to malate (which has its own impact on energy production) is a challenge, although some evidence suggests that the combination is more effective than L-citrulline alone.
Still, plenty of studies tout the benefits of both types of citrulline, so if you’re looking for a pre-workout supplement, it may be worth trying each to see which is more effective for you. And, as you’ll see in a moment, the type of workout you’re trying to improve may determine which type of citrulline you choose.
Why Is Citrulline Important for Exercisers?
To fully understand how citrulline benefits exercise, it’s helpful to first consider what holds us back in our workouts. At the top of that list is our bodies’ inability to process oxygen as efficiently when our heart rate hits a certain point. In cycling — a sport known for athletes with a high VO2 max (the maximum amount of oxygen your body can use during exercise) — L-citrulline was shown to help them cycle longer by improving the exercising muscles’ ability to take in and process oxygen.
When it comes to strength training, that increase of oxygen in the muscles is also extremely beneficial. By increasing the blood flow and oxygen going to those muscles, some studies have shown that citrulline malate may help exercisers significantly increase their number of reps, reduce post-workout muscle soreness, and decrease fatigue.
The Scientific Evidence for Citrulline Supplementation and Exercise
According to the systematic review and meta-analysis of this topic we mentioned in the beginning of this article, results on citrulline’s effectiveness on boosting exercise remain mixed. Some studies showed impressive benefits, while others suggest additional research is required in areas related to performance and muscle soreness.
The authors of the review found that oral L-citrulline and citrulline malate supplementation increase citrulline, arginine, and nitric oxide concentrations. They state that the enhancement of blood flow is proven — and that many studies have reported positive benefits of supplementation when it comes to exercise and recovery.
The review concluded that more research is needed to determine the precise benefits of citrulline. That being said, analysis of the current studies indicates that citrulline supplements can produce a small, but notable, improvement in resistance training, especially in the lower body (where larger muscles need more oxygen and where a boost to nitric oxide would make a bigger difference).
How Much Citrulline Should I Take?
Citrulline is typically well-tolerated, even in higher doses. If you’re trying to figure out the optimal amount for your workout, keep in mind dosing guidelines.
You’ll find that many pre-workout supplements contain between 3 and 6 grams of L-citrulline or up to 8 grams of citrulline malate.
Considerations Before Taking a Supplement
Always refer to the product label of any supplement you intend to take to check for any warnings associated with the product before you take it.
Conclusion
Whether you include L-citrulline or citrulline malate as part of your pre-workout routine, it may help give your fitness routine a boost. Give it a try — and then track your results so you can make the most of every moment in the gym.
