L-Citrulline supplements can reduce symptoms of mild erectile dysfunction by promoting blood flow throughout the body.Shirai, M., Hiramatsu, I., Aoki, Y., Shimoyama, H., Mizuno, T., Nozaki, T., Fukuhara, S., Iwasa, A., Kageyama, S., & Tsujimura, A. (2018). Oral L-citrulline and Transresveratrol Supplementation Improves Erectile Function in Men With Phosphodiesterase 5 Inhibitors: A Randomized, Double-Blind, Placebo-Controlled Crossover Pilot Study. Sexual Medicine, 6(4), 291-296. But ED is a complex issue that may have roots in underlying health conditions, both physical and mental. Even if L-citrulline helps with your ED, it would be wise to speak with a physician about detecting and treating underlying causes.