L-Arginine Sucks



Walk into any supplement shop and talk a good long look at the rows and rows of pre workout they have sitting on the shelves. After you’re done staring at the nice, shiny labels, turn the tub around to take a good look at the ingredients panel. Once you get past the cocktail of stimulants, focus boosters, and vitamins, you’ll arrive at the “Pump Matrix”.


Chances are you’ll see one ingredient in particular included in virtually everyone of those products -- L-Arginine. While you might not be familiar with this ingredient, it’s the amino acid that started the nitric oxide (NO) booster craze back in the 1990s. Back then, NO-boosting supplements were simply nothing but arginine, and they flew off the shelf like hotcakes all with the promise of monstrous pumps and skin-tearing vascularity.


But there’s a dirty little secret out there nobody really knows about…


L-Arginine does NOTHING for nitric oxide production or your pumps!


Numerous studies have shown that orally supplemented l-arginine (the same form used in many pre workouts), even when dosed at 6g/day, has no benefit on nitric oxide production or athletic performance.[1,2,3]


“4 weeks of L-arginine supplementation did not cause beneficial changes in metabolic and hormonal parameters, beyond those achieved with exercise alone”


“The results of this study suggested that short-term arginine supplementation had no effect on nitric oxide production, lactate and ammonia metabolism and performance in intermittent anaerobic exercise in well-trained male athletes.”


So, why is l-arginine still lauded for its nitric oxide boosting benefits and used extensively in pre workouts claiming to enhance the pump?


It all goes back to some early research showing that when used intravenously, l-arginine (at a massive 30g dose) elevated nitric oxide levels in sick and healthy humans.[4,5] The issue is that virtually every single person taking supplements to boost nitric oxide consume them orally.

When l-arginine is supplemented orally, it’s been shown to have no effect compared to an infusion of l-arginine.[4] This is due to ingredient bioavailability.


You see, when you take something intravenously (with an IV), you’re directly infusing it into the bloodstream, guaranteeing 100% bioavailability. However, when consuming something orally, the ingredient must survive the torturous path through the GI system before it can be absorbed in the small intestine and transported into the bloodstream


Here’s where l-arginine runs into a buzzsaw known as your GI. Arginine is rapidly broken down by intestinal arginase and converted to ornithine and urea, leaving it with an incredibly low bioavailability[6] of about 20%, meaning if you consumed 10g of arginine, you’d only absorb about 2g worth. So, a way around this would be to consume 20-30g worth of arginine, but that comes a great deal of GI distress and stomach upset, which isn’t exactly ideal pre workout.[3]


That’s why Primeval Labs Mega Pre contains NO Arginine whatsoever!


L-Citrulline for Proven Results


So, if L-Arginine isn’t particularly effective for boosting nitric oxide in the body, what is?




L-Citrulline is a nonessential amino acid prevalent in watermelon, which has been shown to be extremely effective for improving vasodilation and nitric oxide levels in the body. In fact, l-citrulline is even more effective than l-arginine when it comes to increasing plasma arginine levels in the body.[6] This is is mainly attributed to l-citrulline’s superior bioavailability in the body.


The end result is better nitric oxide production, greater blood flow and vascularity, and massive muscle pumps! With greater blood flow, you’ll experience better energy and endurance during training, due to the increased amounts of oxygen and nutrients constantly shuttled to your muscles.


Mega Pre contains a heaping 6g dose of pure l-citrulline to fuel constant nitric oxide production generating monstrous pumps and those skin-tearing veins you’ve always wanted. But that’s not all!


Mega Pre also includes VasoDrive-AP, a duo of tripeptides that inhibits ACE (angiotensin converting enzyme). ACE is an enzyme that causes blood vessels to constrict, limiting blood flow, nutrient delivery, and pumps. By combining the vasorelaxation abilities of VasoDrive-AP alongside the NO-boosting powers of L-Citrulline, Mega Pre has everything you need for sustained nitric oxide production, giving you better performance and pumps in the gym for substantial gains!



  1. Liu T-H, Wu C-L, Chiang C-W, Lo Y-W, Tseng H-F, Chang C-K. No effect of short-term arginine supplementation on nitric oxide production, metabolism and performance in intermittent exercise in athletes. J Nutr Biochem. 2009;20(6):462-468. doi:10.1016/j.jnutbio.2008.05.005.

  2. Alvares TS, Conte-Junior CA, Silva JT, Paschoalin VMF. L-arginine does not improve biochemical and hormonal response in trained runners  after 4 weeks of supplementation. Nutr Res. 2014;34(1):31-39. doi:10.1016/j.nutres.2013.10.006.

  3. Robinson TM, Sewell DA, Greenhaff PL. L-arginine ingestion after rest and exercise: effects on glucose disposal. Medicine and science in sports and exercise. 2003;35(8):1309-1315.

  4. Bode-Böger SM, Böger RH, Galland A, Tsikas D, Frölich JC. L-arginine-induced vasodilation in healthy humans: pharmacokinetic–pharmacodynamic relationship. British Journal of Clinical Pharmacology. 1998;46(5):489-497. doi:10.1046/j.1365-2125.1998.00803.x.

  5. Bode-Boger SM, Boger RH, Alfke H, et al. L-arginine induces nitric oxide-dependent vasodilation in patients with critical  limb ischemia. A randomized, controlled study. Circulation. 1996;93(1):85-90.

  6. Schwedhelm E, Maas R, Freese R, et al. Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine: impact on nitric oxide metabolism. British journal of clinical pharmacology. 2008;65(1):51-59.