How long does it take for citrulline to start working?

Citrulline, which is most commonly found in dietary supplements in the form of citrulline malate, is a preparation with a wide range of applications. Although it is most often used before physical exercise, it is worth knowing that its properties can also be useful for people with various medical conditions.

1. Characteristics of citrulline
2. The effects of citrulline
3. Duration of citrulline action

However, it is worth noting that healthy people can expect to see results after just a few dozen minutes, while those struggling to improve their health often have to wait a little longer, even weeks.

Characteristics of citrulline

Citrulline, an important amino acid, is not synthesised in the body in the usual way, as is the case with many other amino acids.

The amino acid responsible for detoxification

Its formation is closely related to the urea cycle, which is a key metabolic process that takes place in the liver and is responsible for removing ammonia, a toxic product of protein metabolism, from the body.

In addition, citrulline can also be produced in the body from ornithine, another amino acid involved in the urea cycle. After being produced in the liver, citrulline is transported to the kidneys, where it participates in further transformations.

Citrulline for blood vessels

Unlike classic amino acids, citrulline is not used for the synthesis of body proteins. Its main role is to participate in the removal of ammonia through the urea cycle, and it also serves as a precursor for the synthesis of the amino acid arginine, which is crucial in the production of nitric oxide, an important factor in the regulation of blood vessel tone.

The effects of citrulline

Understanding the mechanism of action of citrulline in the context of urea excretion requires looking at its role as a precursor to arginine. Arginine, an essential amino acid, plays a key role in the urea cycle. This cycle is an important element in the metabolism of nitrogen, a basic element in proteins. As a result, urea, the end product of the urea cycle, is effectively excreted by the kidneys.

What does citrulline supplementation lead to?

Citrulline supplementation leads to increased arginine levels, which in turn can accelerate the processes associated with urea excretion. This phenomenon is particularly important in the context of intense physical exercise, where the management of nitrogen and its by-products, such as urea, is crucial for maintaining metabolic balance.

Effect on blood thinning

When it comes to citrulline's effect on lowering blood pressure, its ability to increase the production of nitric oxide (NO) in the body plays a key role. Nitric oxide is a known vasodilator, which translates into a potential reduction in blood pressure. This effect is particularly important in the context of cardiovascular health, where maintaining adequate blood pressure is fundamental to preventing various diseases, including dementia and premature death.

Citrulline supplementation can therefore be part of a strategy to regulate blood pressure, although it should also be remembered that the dilation of blood vessels, known as vasodilation, is a phenomenon that is important to strength sports enthusiasts, as it is known as the ‘muscle pump’.

The most important functions of citrulline

Duration of citrulline action

The effectiveness of citrulline in the process of urea excretion and in lowering blood pressure depends on many individual factors, such as dosage, digestion time, absorption, and the specifics of a person's metabolism. The time it takes for the expected effects to occur may vary, for example in people who are malnourished or have liver and/or kidney disorders.

Interestingly, the first signs of citrulline's effect on urea excretion may be noticeable within tens or hundreds of minutes after ingestion, but the full effects often only become apparent after regular use for several days or even a week. The same principle applies to the effect of citrulline on blood pressure and physical performance. The initial effects may be visible relatively quickly, but stable and long-term dilation and relaxation of blood vessels often requires a longer period of regular supplementation.

When using citrulline in a pre-workout context, it is most often recommended to consume it about 30-60 minutes before exercise. For long training sessions, the time between consumption and exercise can be shortened. To optimise citrulline metabolism, it is often combined with arginine and ornithine.

Sources:

• Allerton TD, Proctor DN, Stephens JM, Dugas TR, Spielmann G, Irving BA. l-Citrulline Supplementation: Impact on Cardiometabolic Health. Nutrients. 2018 Jul 19;10(7):921. doi: 10.3390/nu10070921. PMID: 30029482; PMCID: PMC6073798.
• Rashid J, Kumar SS, Job KM, Liu X, Fike CD, Sherwin CMT. Therapeutic Potential of Citrulline as an Arginine Supplement: A Clinical Pharmacology Review. Paediatr Drugs. 2020 Jun;22(3):279-293. doi: 10.1007/s40272-020-00384-5. PMID: 32140997; PMCID: PMC7274894