What Is L-Citrulline Powder? L-citrulline powder consists of a nonessential amino acid that is produced naturally by the body. It is most commonly taken by bodybuilders and athletes to improve exercise endurance. L-Citrulline Powder Benefits † L-citrulline powder is most well-known for supporting athletic endurance. It supports the cardiovascular system and heart health and may help fortify the immune system. L-Citrulline may also contribute to sexual health and aid libido. Preworkout Boosts nitric oxide production in the body Boost athletic endurance Support cardiovascular health Promote heart health Fortify immune function Contribute to sexual wellness and aid libido