Nitric-Oxide boosters: Do they improve performance?

Nitric-Oxide (NO) is known to play an active role in “regulating blood flow, mitochondrial respiration, and platelet function”⁷, leading to the common belief that increasing the level of NO in the body will improve the delivery of oxygen and nutrients to muscles that are being worked.  But before discussing whether it works, I first want to introduce the theory of how it works.

There are two well known pathways in which NO synthesis occurs: NO synthase (NOS) dependent and NOS independent.  L-carnitine has shown to increase NO levels, however, the precise pathway it follows is still unknown⁷.  L-arginine and L-citrulline, on the other hand, are precursors for activating the NOS dependent pathway⁷, which may explain why the oral ingestion of L-arginine is a popular choice for those looking to  increase NO levels.  L-arginine also happens to be the supplement of choice for researchers interested in studying the effects of increased NO levels.


The Facts
A review published in the Sports Med journal in 2011 compared studies that had been done using L-arginine as a ergogenic aid - that is studies that used L-arginine as a pre-workout supplement to enhance strength, power, and muscle recovery.  A total of 11 studies were evaluated, five of which concentrated on the short term effects and eight that concentrated on the long term effects.  The results were mixed; three short term studies and four long term studies showed improvement in performance².  The review concluded that,

“…it is still premature to recommend dietary supplements containing L-arginine as an ergogenic aid for healthy physically active subjects.”

Another review published just this month, February 2012, also compared results from studies which looked at L-arginine supplementation to increase performance; however it broke the studies up by the subjects’ level of training.  The result was a remarkable correlation; the less trained you are, the greater benefit you will get from supplementation of L-arginine⁷.  The authors’ state,

“…training status of the subjects seems to be an important factor linked to the ergogenic effect of NO supplementation. Studies involving untrained or moderately trained healthy subjects showed that NO donors could improve tolerance to aerobic and anaerobic exercise. However, when highly trained subjects were supplemented, no positive effect on performance was indicated.”

Also noted is that the subjects used in the studies were predominately young males, and further research on older and female subjects needs to be performed to determine if NO supplementation would be beneficial.

Personal Experience

I recently tried supplementing L-arginine pre-workout after receiving it from my mother-in-law for free.  It was pure L-arginine with no added sugars or chemicals, which was a big plus, but it also meant that it tasted awful.   Awful is not the correct word, It was atrocious.  However, I preferred it this way because I don’t like to consume any artificially made substances or chemicals, or at least try to limit them as much as possible.

I gave it a full eight week trial, one whole bulking cycle, and the only difference I experienced was a bad taste in my mouth.  The difference in my strength and size gains was negligible to what I normally see in a bulk cycle.

L-Arginine Benefits

Just because the supplementation of L-arginine didn’t have an ergogenic effect doesn’t mean that it doesn’t have uses.  In fact supplementation of L-arginine has shown to have a positive effect on various ailments; it will help with endothelial dsyfunction⁵, has been shown to correct and prevent hypertension⁴, improve wound healing time in diabetics¹, reduce high blood pressure⁶, and even decrease blood pressure in women with preeclampsia⁸.

Conclusion

The reviews clearly show that if you are healthy and at least moderately trained, the supplementation of L-arginine, or anything to raise NO levels, will not aid in physical performance.  It is only untrained individuals that see any benefits.  One has to weigh those possible benefits with the consequences; the cost of the supplement, the awful taste, and last but not least, the possibility of serious side effects.  While WebMD does state that serious side effects “are rare in healthy people”, why take the risk?  If you really need a stimulant before your workout, then get some caffeine (I am not talking about those energy drinks full of ingredients you nor I can pronounce, but instead something like green-tea or a cup of strong black coffee).  More on that at another time though.

References

[1]  Barbul, Adrian , Udaya Tantry, Frank J. Thornton, and Maria B. Witte. "L-Arginine supplementation enhances diabetic wound healing." Metabolism - Clinical and Experimental  51.10 (2002): 1269-1273. Metabolism - Clinical and Experimental. Web. 17 Feb. 2012.

[2]  Gomes,  Paschoalin,  Bhambhani,  Meirelles, and  Álvares. "L-Arginine as a potential ergogenic aid in healthy subjects." Sports Med 41.3 (2011): 233-248. PubMed. Web. 15 Feb. 2012.

[3]  Griffin, R. Morgan. "L-Arginine Supplements." WebMD. N.p., n.d. Web. 18 Feb. 2012. <http://www.webmd.com/vitamins-and-supplements/lifestyle-guide-11/supplement-guide-l-arginine>.

[4]  NAGAYA, NORITOSHI . "Short-term Oral Administration of L-Arginine Improves Hemodynamics and Exercise Capacity in Patients with Precapillary Pulmonary Hypertension." American Journal of Respiratory and Critical Care Medicine 163 (2001): 887-891. American Journal of Respiratory and Critical Care Medicine. Web. 14 Feb. 2012.

[5]  Schuler, MD, Gerhard , Stephan Gielen, MDa, Sandra Erbs, BSca, Lutz  Hilbrich, MDa, Rainer Hambrecht, MDa, Eduard Fiehn, MDa, and Nina Schoene, MDa. "Correction of endothelial dysfunction in chronic heart failure." Journal of the American College of Cardiology 35.3 (1999): 706-713. Science Direct. Web. 17 Feb. 2012.

[6]  Strazzullo, Pasquale , Licia Lacovielloc, Roberto Laconeb,  Ermenegilda Paganob, Alfonso Siania, and Francesco Scopacasad. "Blood pressure and metabolic changes during dietary l-arginine supplementation in humans." American Journal of Hypertension 13.5 (2000): 547-551. Science Direct. Web. 15 Feb. 2012.

[7]  Tur JA, Pons A., and Sureda A Bescós R. "The effect of nitric-oxide-related supplements on human performance." Sports Med 42 (2012): n. pag. pubmed.gov. Web. 17 Feb. 2012.

[8]  Zdebski, Z. , R. Korbut, R. Olszanecki, and K. Rytlewski. "Effects of prolonged oral supplementation with l-arginine on blood pressure and nitric oxide synthesis in preeclampsia." European Journal of Clinical Investigation 35.1 (2005): 32-37. Print.