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Citrulline (L-citrulline) is an amino acid produced naturally by the body and also found in some foods, such as watermelon, and to a lesser degree in cucumbers and cantaloupe. The body transforms L-citrulline into another amino acid, L-arginine, and also to nitric oxide. L-citrulline is used for people who suffer with fatigue, dementia, muscle weakness, sickle cell disease, erectile dysfunction, high blood pressure, heart disease, and diabetes. It is believed to work by increasing the supply of nitric oxide and substances the body needs to produce certain proteins, and it may also help dilate veins and arteries to improve blood circulation and reduce blood pressure.
Citrulline and Erectile Dysfunction
Arginine is known to help with erectile dysfunction, however oral use of the amino acid results in extensive presystemic metabolism. L-citrulline converts to arginine in the body and is not subject to presystemic metabolism. Therefore, a team of researchers in Italy set out to test the efficacy and safety of citrulline supplements in improving erection hardness in men who had mild erectile dysfunction.
In the single-blind study, 24 men (mean age 56.5 years) received placebo for one month and then citrulline (1.5 g/day) for one month. Two (8.3%) of the 24 men reported an improvement in erection hardness score from 3 (mild erectile dysfunction) to 4 (normal erectile function) when taking placebo, while 12 (50%) of 24 men reported similar results when taking citrulline. No adverse effects were noted. All the men who reported an improvement in erectile function said they were very satisfied with the results. The study’s authors concluded that at least in the short term, citrulline supplementation is safe and well accepted by patients, and that it warrants further research. (Cormio 2011)
Citrulline and Other Health Benefits
A Japanese study investigated the effect of citrulline supplementation on arterial stiffness in middle-aged men. The double-blind, randomized, placebo-controlled parallel-group trial consisted of 15 healthy men with brachial ankle pulse wave velocity (baPWV) who were given 5.6 g/day of citrulline (8 men) or placebo for seven days. After seven days, baPWV was significantly reduced in men who took citrulline. In addition, levels of nitric oxide metabolic products, plasma citrulline, and arginine also were significantly increased only in the citrulline group. No significant differences in blood pressure were noted between the two groups. The findings suggest that short-term use of citrulline supplementation may improve arterial stiffness, independent of blood pressure. (Ochiai 2010)
In a more recent study, researchers explored the effect of a watermelon supplement (2.7 g citrulline/1.3 g arginine) or placebo on heart rate, brachial systolic blood pressure (BP), brachial pulse pressure, aortic systolic BP, and other hemodynamic measures in four men and five women (mean age, 54 years) who had prehypertension (average, 134/77 mm Hg). The regimen involved taking either the supplement or placebo daily for six weeks followed by a four-week washout period and then crossover.
Compared with placebo and baseline measures, there was a significant effect associated with the watermelon supplement on brachial pulse pressure, aortic systolic blood pressure, aortic PP, and augmentation index. The authors concluded that “watermelon supplementation improves aortic hemodynamics through a decrease in the amplitude of the reflected wave in individuals with prehypertension.” (Figueroa 2011)
Side Effects
No side effects have been reported from the use of citrulline.
How To Take Citrulline
Follow package directions or consult a knowledgeable healthcare practitioner regarding the appropriate dose of citrulline.
References
Cormio L et al. Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction. Urology 2011 Jan; 77(1): 119-22
Figueroa A et al. Effects of watermelon supplementation on aortic blood pressure and wave reflection in individuals with prehypertension: a pilot study. Am J Hypertens 2011 Jan; 24(1): 40-44
Ochiai M et al. Short-term effects of l-citrulline supplementation on arterial stiffness in middle-aged men. Int J Cardiol 2010 Nov 8
