BSN AminoX Review



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AMINOx is BSN’s relatively popular amino-based intra-workout formula. The profile is relatively simple, with an emphasis on the three BCAAs, but does also contain an undisclosed amount of Citrulline, making it sort of unique…[Skip to the Bottom Line]


Leucine is an amino acid that belongs to the group known as branched chain amino acids (BCAAs). In most BCAA products, there is a higher concentration of Leucine than the other two BCAAs. The most common ratio, the ratio found in Pro BCAA, is 2:1:1 of with the higher weight being Leucine. While there is no reliable scientific evidence to indicate one true “optimal ratio”, several studies have confirmed that Leucine is the most important BCAA in regards to muscle protein synthesis. Supplemental Leucine has been shown to increase protein synthesis in rats as well as humans in dozens of studies. A 2012 study found that supplementation with 12 g of L-leucine per day resulted in improved protein synthesis in elderly males consuming a low protein diet, indicating that it may be especially useful for those with low protein intake. Since Leucine is the most studied of the three BCAAs, its mechanism of action has been established. Leucine works via activation of Mammalian Target of Rapamycin (mTOR) which is a signaling protein that signals the body to synthesize protein. To put it simply, Leucine signals mTOR which in turn stimulates protein synthesis.


While Leucine is the most important with regards to muscle protein synthesis, Isoleucine appears to have unique benefits regarding glucose uptake by muscle cells (while lowering blood glucose). In several rat studies, Isoleucine has effectively lowered blood glucose and increased glucose uptake into muscle cells. While the effect of Isoleucine (in isolation) on muscle glucose uptake has not been studied in humans, BCAAs in general due appear to induce glucose uptake, and based on the rat studies this may be due to Isoleucine more so than the others.


Valine appears to possess the least unique benefit, but there are claims circulating that Valine may reduce mental exercise-induced fatigue by reducing the amount of Tryptophan available for Serotonin synthesis. A 2001 study concluded that Valine lowered the amount of exercise-induced 5-HT (Serotonin) in mouse hippocampuses. During exercise Tryptophan is transported to the brain where it is converted into Serotonin. It is hypothesized that Serotonin is responsible for mental fatigue. It has also been established that BCAA directly compete with tryptophan for the same pathway to the brain, and therefore may reduce the amount of Tryptophan available for Serotonin production. This would explain certain subjective anti-fatigue effects of BCAA supplementation noted in a few studies. However, the claim that Valine is solely responsible for this effect is unsubstantiated by human studies. Given the current literature, it appears more likely that BCAAs in general help to attenuate fatigue.


A 2004 study conducted by the American Society for Nutritional Sciences found that BCAA requirement was significantly increased by exercise and that supplementation had “beneficial effects for decreasing exercise-induced muscle damage and promoting muscle-protein synthesis”. A second study, published in the “American Journal of Physiology-Endocrinology and Metabolism”, found that while BCAA intake did not seem to affect amino acid concentration during exercise, it did have a protein-sparing effect during recovery. If you consume a diet rich in complete proteins, then you already receive enough dietary BCAAs to fulfill all normal physiological functions. However, this in no way means you cannot derive added benefit from supplementing with BCAAs.

A 2009 study published in the “Journal of the International Society of Sports Nutrition” tested the effects of BCAA supplementation in comparison to whey protein supplementation or simple carbohydrates (from a sports drink) in athletes. All subjects consumed the same diet and participated in the same physical training regimen. At the end of the 8 week study, the BCAA group significantly outperformed both the whey group and carbohydrate group in terms of lean body mass as well as strength. Results like these make us question whether skeptics of BCAAs have even bothered to read the literature. There is more than enough evidence to conclude that BCAA supplementation can have a significant anabolic effect in both protein deficient AND non-protein deficient humans.

A major criticism of BCAA supplements is that Leucine alone can achieve a significant increase in muscle protein synthesis. While Leucine does appear to be the most critical in regards to muscle protein synthesis, a 2009 study published in the “Journal of the International Society of Sports Nutrition” concluded that BCAAs (2:1:1) have a more pronounced effect on protein synthesis than the same amount of Leucine alone. So, theoretically speaking, if you had to choose, you would choose Leucine, but all three is undeniably a better way to go.


L-Alanine is an amino acid, the primary function of which (aside from building proteins) pertain to glucose metabolism and the transport of nitrogen to the liver. In a 2010 double-blind placebo controlled study, published in the FASEB Journal, it was shown that L-alanine supplementation slightly reduced delayed onset muscle soreness. However, there is some controversy as to whether including l-alanine with other amino acids may result in absorption issues due to competition. No studies have been conducted to determine whether this hypothesis is correct, so we prefer to disregard it as fact for now.


Contrary to popular belief, Taurine is not a stimulant but rather an an amino acid with anti-oxidant properties. In a 2011 study, Taurine was shown to significantly decrease oxidative stress in skeletal muscle following exercise. Prior to that, a 2004 study showed that Taurine may decrease exercise induced DNA damage, as well as “enhance the capacity of exercise due to its cellular protective properties”. A recent 2013 study noted a 1.7% improvement in 3k-time trial of runners after supplementing with Taurine, but noted that more research would be required to determine the exact mechanism of action.

It’s unfortunate that Taurine has developed a sort of stigma because of its inclusion in energy drinks. While Taurine does not provide “energy” in the way that caffeine does, several studies have shown its effectiveness as an antioxidant with workout-enhancing properties, and while the exact mechanism of action remains unknown, it appears likely that Taurine may improve exercise performance by reducing some of the cellular oxidative damage that generally leads to fatigue. The usual dose of Taurine used for performance enhancement is about 1 gram.


Citrulline is a precursor to the amino acid Arginine, which is a precursor to Nitric Oxide (NO). A 2009 study, published in the “Journal of Free Radical Research”, found that 6 grams of Citrulline Malate given to male cyclists before a race increased “plasma Arginine availability for NO synthesis and PMNs priming for oxidative burst without oxidative damage”.

You may be wondering: How can Citrulline be more effective at increasing Arginine than Arginine itself? The problem with supplemental Arginine is that it is metabolized in the intestines and liver into other substances such as Ornithine and Urea. The intestines and liver contain relatively high levels of Arginase, the enzyme that converts Arginine to Ornithine and Urea. As a result, very little goes on to be involved with the synthesis of NO because it is being diverted for other purposes. Citrulline, on the other hand, is able to bypass the liver and is metabolized into Arginine elsewhere, where not as much Arginase is present. Thus, more of the Arginine is able to convert into NO.

A 2002 study, published in the “British Journal of Sports Medicine” found that Citrulline supplementation (6g/day for 15 days) significantly increased ATP production during exercise in healthy adult males. A 2011 study, the subjects of which were rats, found that supplemental Citrulline increased muscular contraction efficiency (less ATP was required for the same amount of power), in-line with the findings of the above-mentioned human study.

With regards to its inclusion in the AMINOx formula: There is preliminary evidence to suggest Citrulline may act in a synergistic manner with Leucine by positively affecting leucine’s stimulation of mTOR. However, this is currently only a theory and has yet to be proven. Furthermore, the exact amount of Citrulline present in the AMINOx formula is undisclosed so we cannot possibly be certain about how effective, or synergistic, it really is in this case.


Malic Acid is a naturally occurring compound, found in particularly high levels in green apples and responsible for the tart taste. Malic Acid plays an important role in the Krebs Cycle (also known as the Citric Acid Cycle), the process by which the body generates energy from the macronutrients (protein, carbs, and fat) we consume. It is commonly alleged that Malic Acid supplementation may improve physical performance, as evidenced in a 2007 study in which mice that were treated with Malic Acid demonstrated improved stamina (swimming). However, no human studies have been conducted to further test these findings.


Citric Acid is a necessary component of the Krebs Cycle, also known as the Citric Acid Cycle. It is alleged to reduce acidity which could theoretically increase time to fatigue in the exercising muscle. However, studies assessing the implications of Citric Acid for exercise are entirely non-existent.


Sodium Bicarbonate, also known as Baking Soda, is an effective intracellular, reducing acidosis in the working muscle in a similar manner as Beta-Alanine. Several studies have demonstrated the ability the performance enhancing effects of Sodium Bicarbonate with most of the benefit being observed in longer-term exercise (when intra-cellular fatigue is more of an issue).


AMINOx is one of the more simplistic but complete BCAA formulas we’ve reviewed. BCAAs, Citrulline, and Taurine are all quite scientifically validated ingredients, and the addition of certain anti-fatigue ingredients further enhances the intra-workout potential of AMINOx. The only issue with the formula is that we can’t be sure of the exact amount of each ingredient. That being said, 10g is more than enough to include relatively effective amounts of the major ingredients. Ultimately, AMINOx is an effective pre/intra-workout formula and at about 60 cents per serving, is very appropriately priced relative to reconstruction cost.

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