Background　L-Citrulline, a potent precursor of L-arginine, is an α-amino acid which is known to be effective in enhancing nitric oxide synthase-catalyzed nitric oxide production, which is involved in vasodilation. The objective of this study was to evaluate the effect of supplemented L-citrulline on swelling of the lower leg in females.
Methods　In a double-blind, randomized, placebo-controlled cross-over protocol, 11 healthy female volunteers（26.9±2.1 years old）received L-citrulline（3.2 g／day）or placebo for 5 days. On day 1（single administration）and day 5（continuous administration）, the circumference of the lower leg and the pooled urine weight during long-term seating and oral water loading were measured.
Results　Long-term seating stress caused the leg swelling remarkably. Compared with the placebo trial, the increment in the circumference of the lower leg during long-term seating stress was significantly reduced in the L-citrulline trial. No significant change in the pooled urine weight was observed in the two trials.
Conclusions　These results indicate that L-citrulline supplementation is useful for reducing leg swelling induced by long-term seating stress in females, probably due to improving peripheral circulation without a diuretic effect.