I first tried l-arginine several months ago after seeing this post: http://forums.phoenixrising.me/inde...since-starting-nitric-oxide-supplement.43761/ and reacted very badly to l-arginine, got very tired. Dang! Then I recently did another experiment thinking the arginine may have depleted my phosphorus (via refeeding syndrome mechanism) but again I got severely fatigued after 3 days on the l-arginine despite taking high phosphorus foods. And then I discovered that l-arginine lowers cortisol: http://www.ncbi.nlm.nih.gov/pubmed/17510493 http://www.livestrong.com/article/526970-l-arginine-and-anxiety/ I upped my adrenal glandular (Drenamin) quite a bit and added in some licorice and my energy is returning. I know some people have had great results with arginine products -- this just shows to me how different we all are, though similar in so many ways too - we all seem to have different processes occurring. I'm hoping like everyone here that Ron Davis will be able to shed some light on all these mysteries!