What is L-Norvaline?
L-norvaline is an amino acid, it's rather uncommon and most sources are synthetic, but it does occur naturally.
It's an isomer of the branch chain amino acid valine, but norvaline is a non branched amino acid.
It appears in a number of "pump" based pre-workouts because of its role as an arginase inhibitor.[2,3]
If you aren't sure what that is, don't feel alone... it's a pretty complex subject, but we're going to give you a simple and to the point explanation.
What are the benefits?
In order to understand the benefits of L-norvaline, you need to have some general background information on the nitric oxide (NO) cycle.
As you can see in the graphic on the right, arginine is required for the production of NO.
It's not that simple though, arginine isn't always used to produce NO. There are two major enzymes that compete for arginine, nitric oxide synthase (NOS) and arginase.[4,5]
When arginine is metabolized by NOS, it gets converted into either nitric oxide (NO) or citrulline. On the other hand, if the arginine gets broken down by arginase, it becomes either ornithine or urea.[6,7]
What does all of this have to do with l-norvaline?
It's simple... L-norvaline blocks arginase from breaking down arginine.
In turn, this allows the arginine to get broken down by NOS, which ultimately leads to a greater rate of conversion to NO. It's this reason that norvaline makes an excellent addition to arginine supplements.
You can think of norvaline as the guard dog protecting your arginine from getting broken down into urea.
The "not so nice" side of norvaline
There is a dark side to norvaline...
Due to it's inhibitory effect on the synthesis of urea, over time l-norvaline can cause an ammonia buildup.
The good news is, these effects can be negated by another NO booster, citrulline.
Citrulline has been proven to be extremely effective at clearing ammonia from the body.[9,10,11] As mentioned above, it provides an even greater boost in NO synthesis.
You can read more on our citrulline page for more information.
The takeaway message here is:
Be careful if you are going to use l-norvaline as a standalone supplement. If you decide to go that route, you'll need to have a strategy in place for preventing an ammonia build up.
The bottom line
L-norvaline is a potent compound with a lot to offer, however, you have to use it wisely. You can greatly increase both the safety and efficacy of l-norvaline when you stack it with arginine, and citrulline.
It will work hand-in-hand with your arginine supplement, protecting it from getting broken down into waste - thus increasing the rate of nitric oxide synthesis. The citrulline will lend further support to the synthesis of nitric oxide, while simultaneously counteracting the ammonia buildup brought on by l-norvaline.
- Merriam-Webster; "Norvaline;"
- Pokrovskiy M., et al.; International journal of hypertension; "Arginase Inhibitor in the Pharmacological Correction of Endothelial Dysfunction;" June 2011
- Ming XF., et al.; BMC cardiovascular disorders; "Inhibition of S6K1 accounts partially for the anti-inflammatory effects of the arginase inhibitor L-norvaline;" March 2009
- Chang CI., et al.; The American journal of physiology; "Arginase modulates nitric oxide production in activated macrophages;" January 1998
- Priyanka D., et al.; PLOS Pathogens; "Modulation of the Arginase Pathway in the Context of Microbial Pathogenesis: A Metabolic Enzyme Moonlighting as an Immune Modulator;" June 2010
- Yang Z., Ming XF.; Current hypertension reports; "Endothelial arginase: a new target in atherosclerosis;" April 2006
- Mori M., Gotoh T.; Biochemical and biophysical research communications; "Regulation of nitric oxide production by arginine metabolic enzymes;" September 2000
- Takeyori S., et al.; The journal of biochemistry; "Regulation of Urea Synthesis in Rat LiverInhibition of Urea Synthesis by L-Norvaline;" March 1979
- Rabier D., Kamoun P.; Amino Acids; "Metabolism of citrulline in man;" 1995
- Callis A., et al.; Arzneimittel-Forschung; "Activity of citrulline malate on acid-base balance and blood ammonia and amino acid levels. Study in the animal and in man;" June 1991
- Kaore SN., et al.; Fundamental & clinical pharmacology; "Citrulline: pharmacological perspectives and its role as an emerging biomarker in future;" February 2013