Description

Citrulline is divided into 2 main types commonly found in functional foods. L-Citrulline is a supplement with Citrulline, and no other supplements are used by the body. Citrulline malate, on the other hand, has a combination of malate, so it plays a role in the production of energy.

L-citrulline, an α-amino acid, contributes to Nitric oxide (NO) synthesis through this NOS-dependent pathway via its conversion to L-arginine. Polyphenols may enhance NO production by increasing eNOS expression and activity and promote NO bioavailability via their antioxidant effects, which protect NO from breakdown by reactive oxygen species (ROS). Within the NOS-independent pathway, nitrate (NO3-) is reduced to nitrite (NO2-) and then NO. Thus, it is proposed that NO availability may be improved by increasing the availability of NO3-, NO2-, L-arginine, L-citrulline, or polyphenols[1].

Food source

There is no set amount of l-citrulline that each person needs per day. Instead, people with particular health needs or susceptibility to conditions supported by increased nitric oxide might benefit from eating more foods high in l-citrulline and taking l-citrulline supplements.

1. Red Watermelon

When it comes to fruits with the most citrulline, watermelon tops the charts. The name citrulline comes from "citrullus," which is the Latin word for watermelon, according to the National Library of Medicine.

The citrulline in watermelon has the potential to act as an antioxidant, according to a June 2005 study in the ?Journal of Chromatography?. It also contains the natural antioxidant lycopene, which gives it its red colour.

2. Yellow Watermelon

Though not as popular as red varieties, watermelon with yellow flesh is another good source of citrulline. Like other types of watermelon, it's rich in the antioxidant vitamin C and is very hydrating.

3. Casaba Melons

The casaba-type melon was found to a top source of citrulline, according to a March 2019 study in the ?Journal of Horticulturae?. This type of melon belongs to a group that also includes honeydew and may have similar nutritional benefits, including providing fibre and small amounts of many vitamins and minerals, all with minimal calories and no fat, per the University of Florida.

4. Cucumbers

Cucumbers have citrulline because they're part of the same family as watermelon, called Cucurbitaceae. Like watermelon, cucumbers are very hydrating and have 97 per cent water.

Benefits

L-Arginine is an essential amino acid and a precursor for synthesising vascular nitric oxide, while L-Citrulline is a non-essential amino acid substrate for increasing L-arginine. Both L-arginine and L-Citrulline in translational studies may acutely lower blood pressure[2]. Current meta-analysis for L-arginine or L-Citrulline interventions in blood pressure have identified significant heterogeneity.

References

[1] Noah M A d’Unienville. “Effect of food sources of nitrate, polyphenols, L-arginine and L-citrulline on endurance exercise performance: a systematic review and meta-analysis of randomised controlled trials.” Journal of the International Society of Sports Nutrition (2021): 76.

[2] Hillsley, Ashley and C. McLachlan. “Assessment of Registered Clinical Trial Designs: Comparison of L-Arginine and/or L-Citrulline Interventions for Hypertension.” Pharmaceuticals 32 18 (2024).