Citrulline: good or bad for sleep?

Citrulline: definition and health benefits

Citrulline, or L-citrulline, is an amino acid that occurs naturally in the body.

In particular, it helps to remove excess toxic ammonia from the body by converting it into urea, a much less harmful substance which can then be excreted by the kidneys via urine.

Citrulline is also converted into arginine in the body, a precursor of nitric oxide (NO). This gas promotes vasodilation, which is important for maintaining blood flow and cardiovascular health. Increasing citrulline intake is sometimes recommended for improving the quality of erections.

Through its effect on the circulation, citrulline also supports stamina and physical performance, and is thus particularly popular with sportspeople.

This amino acid also plays a role in muscle recovery by facilitating the removal of metabolic waste products from muscles (often associated with muscle fatigue).

What are the best sources of citrulline?

Citrulline-rich foods

Small amounts of citrulline are found in several fruits and vegetables, including watermelon, known scientifically as Citrullus lanatus from which it takes its name, and other cucurbits such as cucumber, melon, pumpkin and squash.

Citrulline supplements

Sportspeople often take extra citrulline on top of that provided by the diet in the form of dietary supplements which provide a much higher dose (such as L-Citrulline). In supplements, citrulline has zero or negligible taste and is thus particularly easy to take.

If you want to supplement with citrulline, be sure to consult a health professional. It’s particularly important to seek medical advice if you suffer from heart disease (especially if you're on medication that affects blood pressure), kidney disease or liver disease, if you are pregnant or breast-feeding, have abnormal intestinal absorption, or are affected by citrullinemia (a urea disorder).

Citrulline: harmful or beneficial to sleep?

How can citrulline affect sleep?

It’s reasonable to question citrulline’s effects on sleep, given that obtaining restful sleep is a key concern for sportspeople as it is for anyone wishing to maintain good physical and mental health.

Though research is limited, the early signs are positive: taking citrulline may actually promote better sleep since it improves the circulation (which leads to better control of body temperature, good nutrient distribution, effective elimination of waste products …) and reduces muscle tension.

An animal study suggests it also has a cardioprotective effect in the case of obstructive sleep apnoea (1).

In addition, several studies have concluded that arginine (the amino acid obtained from citrulline) plays a role in regulating variables of sleep quality or at least does not impair sleep (2-4).

Summary of citrulline’s effects on sleep

In short, citrulline appears to have no negative effects on sleep.

Existing data suggests that in principle, taking citrulline presents no risk to sleep quality, indeed quite the contrary.

Of course, since everyone responds differently to supplementation, it is ultimately up to you to establish whether citrulline affects your ability to fall asleep and get a good night’s sleep.

The best supplements for sleep problems

If you’re specifically looking for a supplement to help with insomnia, we’d recommend focusing on the following (whether alongside citrulline or not):

• melatonin, alias the ‘sleep hormone’ (such as in the product Melatonin Spray);
• relaxing plants like valerian and California poppy (try Natural Sleep Formula);