For you nitric oxide/arginine users, I hope you kept your receipts.
Just released in the prestigious Journal of Nutrition was an article that took an involved approach to studying the ergogenic potential of arginine. As many of you likely know, supplementation with arginine has been one of the most popular forms of supplementation in the last ten years.
Briefly, arginine is an amino acid considered by many to be conditionally essential and was most supported initially for its ability to enhance growth hormone levels. In this respect, a number of early studies reported a 2.7-fold increase in growth hormone levels 60 min after after ingesting 1.5 grams of arginine and lysine in clinically ill populations (Suminski et al. 1997). A separate study showed a significant increase in young males 30 minutes after 1.2 grams of arginine and 1.2 grams of lysine, while growth hormone levels after 90 minutes were increased almost 8-fold, however, this response required both amino acids be ingested together (Isidori et al. 1981). In addition, arginine administration was shown in various non-human research models to increase nitric oxide synthesis and promote vasodilation and for all intent purposes, the beast was released (Kingwell 2000).
Popularity for NO-modulators soared, but an overall lack of supportive data existed. To their credit, the makers of NO2 funded what is still today one of the few training studies which employed arginine supplementation while resistance training over several weeks. Very modest improvements in peak power production in the legs and maximal bench press strength were found (Campbell et al. 2006). Several years after that, a study was completed using NO-Shotgun and reported many positive effects, but considering the other ingredients provided (essential amino acids and creatine in addition to arginine) it could not effectively be determined any specific impact of arginine (Shelmadine et al. 2009).
Researchers from the University of Memphis followed with a study comparing Alpha-GPC to other purported nitric oxide modulators and reported that none of the NO modulators increased NO to a similar degree as Alpha-GPC (Bloomer et al. 2010).
This leads us to the study recently published by a well-known research group out of McMaster University in Canada (Tang et al. 2010). The researchers designed a study to determine the impact of 10 grams of arginine supplementation on the synthesis of nitric oxide, blood flow within muscle tissue and protein synthesis inside muscle tissue after an exercise bout. All subjects completed two exercise bouts where in one condition they ingested 10 grams of arginine along with 10 grams of essential amino acids or they ingested 20 grams of a control protein. Ten grams of arginine is a healthy dose and more than what is typically provided in most formulations, and quite a bit more than what was initially to increase growth hormone levels. An additional ten grams of essential amino acids was provided to ensure muscle protein synthetic mechanisms were activated and also that enough of the necessary building blocks were in place in case arginine did stimulate an increase in muscle building. A total of 20 grams of amino acids were provided in the control group to allow the researchers to accurately evaluate any change which may have occurred in the arginine + EAA group. As expected, arginine administration increased arginine levels in the blood, but this increase did nothing to increase production of nitric oxide. Similarly, blood flow increased after exercise (as it should have), but including arginine did nothing to change blood flow. According to this data, arginine does nothing to increase blood flow, vasodilation, etc., which is why I hope you kept your receipt. The last shred of hope would be if for some reason rates of protein synthesis increased after arginine was provided, but this wasn’t found either as exercise resulted in an increase in muscle protein synthesis, but arginine inclusion was the same as when amino acids were provided.
While it’s never safe to draw strong conclusions from one study, that’s not the message to be derived from this article. When looking at all the available scientific literature, the data overall just doesn’t support using arginine or any other nutrient to increase nitric oxide production to improve your health and how you respond to your exercise program.
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