An Evaluation of L-Arginine as a Performance Booster

INTRODUCTION

 L-Arginine, an amino acid, has also been an integral amino acid within our bodies. It wasn’t until 1886 when Ernst Schulze, a German Scientist, isolated Arginine from pumpkin seedlings (13). Since the discovery, the effects of L-Arginine has been widely interpreted, manipulated, and utilized to increase the performance of athletes and people alike. The most prominent claims revolving around this supplement within scientific journals was its effective role in power output and strength, vasodilation through increase of Nitric Oxide, and antioxidative stress management. The accuracy of these claims will be evaluated in order to uncover the truth about L-Arginine.

 L-Arginine is a conditionally essential amino acid meaning it can either be produced by the body naturally or acquire through nutrition during times of physiological stress. L-Arginine can be found in any protein containing item. Overconsumption may lead to a small amount of side effects such as indigestion, nausea, diarrhea, airway inflammation, or even low blood pressure. Be sure to consult with a doctor or consume in a controlled environment in order to reduce side effects. As an amino acid it has roles in healing, vascular health, immune activity, and protein production. It is most known as a substrate to create Nitric Oxide which dilates blood vessels thus increasing nutrient delivery and athletic performance (5).

POWER/PERFORMANCE

The first set of articles identified L-Arginine’s role as a performance booster, in order to get a better “pump” or simply push more weight or run faster. The first set of studies on L-Arginine had the intention to test the benefits towards human performance. Collectively, the first group of articles tested either performance, upper body muscle strength, or exercise capacity. There were multiple methods as to how these properties were examined. In a study by Robert Soderman, human performance was evaluated by having thirty-five track and field athletes, college males and females, perform two exercise trials using a windgate Anaerobic Power Cycle Ergometer Test with L-Arginine supplementation or a placebo lasting 30 seconds (13).

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The results of this study showed that peak power did appear to be higher in the supplemented group rather than the control group. This study also mentioned that peak power was reached very early yet their average power throughout the whole test had no significant change, proving that L-Ariginine benefits athlete’s explosive ability in the short term (13). In a study by, Andrew Quesada, L-Arginine supplementation was observed on the muscular strength of the upper body. Twenty males in college with an average weight and fat percentage, participated in a random, double blind study (10). After 8 weeks of 12g/day supplementation of L-Arginine or a placebo the participants were told to perform a one rep max bench press and then how many reps at 85% of max could be performed at weeks 1, 3, 5, and 8 (10). Although there wasn’t significant change, the 1RM of those individuals that consumed the L-Arginine increased their max by 12kg by the end of the study while the control only improved by 3kg (10).The number of repetitions of the supplemented group also appeared to be greater than the control. This study reinforces the idea that L-Arginine supplementation does in fact increase nutrient delivery, allowing people to lift more weights.

Another study, by Yulia Lomonosova, observing rats, assessed that L-Arginine could reduce exercise induced damage (8). This study suggested that L-Arginine supplementation before eccentric contractions could remove exercise-induced damage. In a test on mice using a control, effective, effective with L-Arginine, and effective with inhibitor group, L-Arginine was deemed effective once again (8). L-Arginine was observed to protect against post-exercise damage to the sarcolemma and reduce the number of actual damaged muscle. This means that L-Arginine, in this study can be used to reduce too many muscle tears thus reducing recovery times. The last study in this section, performed by Stéphane Doutreleau observed the effectiveness of L-Arginine when it came to heart transplant patients.  In a double blind study Heart transplant patients performed a 6 minute walk test and a maximal bike test initially and at 6 weeks (4). The results showed of course the exercise capacity of heart transplant patients decreased but, their quality of life increased and submaximal exercise capacity improved (4). After heart transplants the endothelium is weakened and L-Arginine strengthened the endothelium recovery (4).

 This first set of articles did in fact support the claims of L-Arginine improving the power output aid of this amino acid. It makes an observable difference in the vascularization of those that underwent the experiments. These studies didn’t seem to have a large group of participants, the Soderman and Quesada tests were done at University of Wisconsin and California State University Fresno respectively, so these studies were credible, yet only contained a niche group of college athletes (13, 10). The rat study group had an adequate amount of participants, 56 mice, but did not mention other diet factors that could have affected the results (8). All of these studies were done by clinical biologists, from Universities, Medicine Faculty Physiology Institute, or a publishing in the American Journal of Clinical Nutrition

VASODILATION (NO2 Production)

 This next set of articles was used to examine the vasodilation effects of L-Arginine. L-Arginine is a precursor to Nitric Oxide which is directly related to dilating blood vessels thus transporting more nutrients throughout the body. NO2 operates by relaxing the blood vessels, allowing more blood to flow with less resistance. This first study done by da Silveira Alvares and published in theMedicine & Science in Sports & Exercise Journal, “Effect of L-arginine Supplementation on Plasma Citrulline and Ornithine” (3). This study was used to observe which pathways use L-Arginine and the methods used here contained 15 trained males in a random, double blind study (3). They were split into an L-Arginine supplemented group and a placebo group, their blood was drawn at intervals during an exercise test that lasted 120 minutes (3). This study concluded that there was definitely increased levels of plasma arginine during exercise. This is important because it proves that L-Arginine is preferred by the Urea Cycle thus being the main substrate to regulate Nitric Oxide Synthase which creates NO2 (3). The next study published in the Biochemical and Biophysical Research Communications Journal by Masahiko Morita indicated that increased plasma L-Arginine enhanced NO bioavailability (9). Rats or New Zealand white rabbits were given L-Citrulline or L-Arginine or both to examine plasma L-Arginine levels (9). Blood flow was significantly increased and the plasma L-Arginine is a direct component of that. What was concluded in this study was that L-Arginine may be used in the future to regulate cardiovascular function or simply increase blood flow. This next study sort of builds of the last. Done by Soyoung Shin in the same journal, to examine the activation of Nitric Oxide Synthase (12). This study determined that intracellular Arginine does not determine NO production, rather extracellular Arginine, the plasma Arginine (12). The “l-arginine paradox” as defined by Nakaki, T, states that “exogenous L-arginine causes NO-mediated biological effects despite the fact that nitric oxide synthases are theoretically saturated with the substrate L-arginine (6). So this is saying that L-Arginine is responsible for Nitric Oxide production and not the dependence of Nitric Oxide Synthases. Extracellular L-Arginine, that being transported freely is what is responsible for the dilation of blood cells.

Once again, these studies further supported claims that L-Arginine is effective in dilating blood vessels, thus increasing nutrient delivery and boosting performance. Extracellular L-Arginine is responsible for NO2 production, L-Arginine, when compared to L-Citrulline, is considered the more favorable substrate to use in the Nitric Oxide Synthase, and that an increase in plasma L-Arginine enhances Nitric Oxide Bioavailability. One strength regarding these research studies where that they observed chemical impact rather than human performance. The study done by Soyoung Shin was done within a lab culture and the results reported, were translated to relate to how it would work within the human body (12). A weakness observed was that these lab studies are not always reliable due to the fact that within a laboratory setting, results not explicitly done to the body may show different results. Although L-Arginine was isolated within a lab study, I believe actual animal trials should be undergone before any misleading assumptions are shared. Morita, is a part of a function research group and da Silveira was published in the Medicine & Science in Sports & Exercise Journal, both studies appear to be quite reliable (9,12).

HEALTH MANAGEMENT

The last section of claim investigation regards L-Arginine and its use in improving our health, not just athletic performance. L-Arginine has been said to play a role in immune function, and balancing oxidative stressors. The first study here observes L-Arginine as an ergogenic aid in healthy subjects. Conducted by Thiago S. Álvares, regarding sports medicine, the effectiveness of nutrient delivery to healthy subjects was observed in a few recent studies and through an analysis Álvares concluded, it is too early to recommend dietary supplements containing L-arginine as an ergogenic aid for healthy physically active subjects. He compiled research from a few other L-Arginine studies that tested the physical effects of L-Arginine and although positive outcomes were demonstrated, “since none of the reports investigated the underlying mechanisms. It is inconclusive to claim the effects were due to increased NO production via L-arginine supplementation” (1). The majority of what was researched had positive results surrounding the performance of those that supplemented with L-Arginine yet Álvares believes more research must be done. The last study conducted by Lingling Shan at the Department of Biochemistry Pharmacy, School of Chemistry and Life Science, SuZhou University, China, observes L-Arginine’s ability to manage oxidative stress. Within this study 48 rats were divided into six groups, a control, one where the rat swam until exhaustion, and another where it swam daily for 8 weeks, each group had regular test subjects and test subjects with L-Arginine supplementation (11). After the exercise tests, oxidative stress was observed within the fatigued rats. Through the L-Arginine supplement exercise-induced activation of NO synthase did not initially occur and increased Nitric Oxide and anti-superoxide levels (11). Interpreting this data it can be concluded that L-Arginine is responsible for reducing exercise-induced imbalances of oxidative stress and its antioxidant defense capacity (11). L-Arginine is responsible in slowing the increase of free radicals and managing the impact of oxidative stress. If imbalances are present within the body L-Arginine can activate the Nitric Oxide pathway to support cell function under stress.

According to the first article in this section, Álvares, analyzed multiple studies concerning L-Arginine being beneficial when it comes to physical activity or activation of vasodilation, yet disagreed with the claims that L-Arginine is responsible for the dilating blood cells. He believed in these studies it was unclear the exact cause of the effects. This article was helpful because it contained many other studies within it yet disagreed with the claims that were being proven elsewhere. A weakness this article contained was that it briefly mentioned the other studies he was examining rather than provide more information about them, which one could look up themselves. The Chinese study on rats examining oxidative stress was beneficial to determine L-Arginine’s effectiveness. The study seemed to be organized well enough to obtain accurate results with a clear determinant that L-Arginine worked. One weakness I could think of is the small sample size during the rat study. If more rats were used it may be possible to provide more confidence in determining the effectiveness of the results. Both of these studies were published in a Sports Medicine Journal or the Journal of Applied Physiology thus granting them credible.

OVERALL CONCLUSION

 After researching the effectiveness of L-Arginine as a sports supplement, many of the popular claims proved to have actual significance and proved clear results. L-Arginine, in conjugation with proper nutrition can be a useful ergogenic aid. As a precursor to Nitric Oxide, its role in vasodilation benefits the body through increased nutrient delivery, improved athletic performance and reduced exercise-induced oxidative stress. Of course like many sports supplements, much more research must be done before determining the safety of everyday supplementation to boost performance. The research articles examined all deemed credible and were beneficial at bringing some light into L-Arginine and its mechanisms of action. It is possible that L-Arginine will be incorporated more within sports supplements in order to gain that extra edge when performing.

References

1. Álvares, T., Meirelles, S., Bhambhani, C., Paschoalin, M., & Gomes, Y. (2011). L-Arginine as a Potential Ergogenic Aidin Healthy Subjects. Sports Medicine, 41(3), 233-248.
2. Apel, Frank (July 2015). “Biographie von Ernst Schulze” (PDF). Retrieved 2017-11-06.
3. Da Silveira Alvares, T. A., Conte-Junior, C. M., Paschoalin, V. T., Silva, J. S., De Mello Meirelles, C., Bhambhani, Y., & Gomes, P. (2011). Effect of L-arginine Supplementation on Plasma Citrulline and Ornithine at Rest and After Resistance Exercise: 2226: Board #103 June 2 2:00 PM – 3:30 PM. Medicine & Science in Sports & Exercise, 43(5 Suppl 1), 590.
4. Doutreleau, Stephane, Rouyer, Olivier, Di Marco, Paola, Lonsdorfer, Evelyne, Richard, Ruddy, Piquard, Francois, & Geny, Bernard. (2010). L-Arginine supplementation improves exercise capacity after a heart transplant. American Journal of Clinical Nutrition, 91(5), 1261-1267.
5. L-arginine. (2005). Alternative Medicine Review, 10(2), 139-147.
6. L-arginine, Emedicince Health. WebMD. https://www.emedicinehealth.com/l-arginine/vitamins-supplements.htm
7. Linden, Wadley, Garnham, & Mcconell. (2011). Effect of l-Arginine Infusion on Glucose Disposal during Exercise in Humans. Medicine & Science in Sports & Exercise, 43(9), 1626-1634.
8. Lomonosova YN, Shenkman BS, Kalamkarov GR, Kostrominova TY, Nemirovskaya TL. L-arginine supplementation protects exercise performance and structural integrity of muscle fibers after a single bout of eccentric exercise in rats. PLoS One. 2014;9(4):e94448. Published 2014 Apr 15. doi:10.1371/journal.pone.0094448
9. Morita, M., Hayashi, T., Ochiai, M., Maeda, M., Yamaguchi, T., Ina, K., & Kuzuya, M. (2014). Oral supplementation with a combination of L-citrulline and L-arginine rapidly increases plasma L-arginine concentration and enhances NO bioavailability. Biochemical and Biophysical Research Communications, 454(1), 53-7.
10. Quesada, A. S., Jackson, C. G., Greer, F. A., & Anderson, T. R. (2011). Effects of L-arginine Supplementation on Upper Body Muscular Strength in Male Recreational Body Builders: 2227: Board #104 June 2 2:00 PM – 3:30 PM. Medicine & Science in Sports & Exercise, 43(5 Suppl 1), 590.
11. Shan, L., Wang, B., Gao, G., Cao, W., & Zhang, Y. (2013). L-Arginine supplementation improves antioxidant defenses through L-arginine/nitric oxide pathways in exercised rats. Journal of Applied Physiology (Bethesda, Md. : 1985), 115(8), 1146-55.
12. Shin, Mohan, & Fung. (2011). Intracellular l-arginine concentration does not determine NO production in endothelial cells: Implications on the “l-arginine paradox”. Biochemical and Biophysical Research Communications,414(4), 660-663.
13. Soderman, R., & Albrechtsen, S. (2014). Over-the-counter L- Arginine Supplements To Improve Power In Track And Field: 165 Board #3 May 28, 9. Medicine & Science in Sports & Exercise, 46, 30.