Reviews

Scivation Xtend Review

Xtend is arguably the most well-known BCAA supplement, though over the years the formula has changed slightly and Scivation has come out with several sequels including the upcoming Xtend GO

Scivation Xtend

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L-LEUCINE

Leucine is an amino acid that belongs to the group known as branched chain amino acids (BCAAs). If you have ever purchased a BCAA product, you may have noticed that it contains more leucine than the other two BCAAs (isoleucine and valine). The ratio is generally something along the lines of 2:1:1, but we’ve seen as much as 8:1:1 in favor of leucine.

Xtend contains the standard 2:1:1 ratio of leucine, isoleucine, and valine respectively. While no study has ever proved that there is an “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.

Most recently, 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. However, leucine has been shown to be effective at dosages ranging from 2-5 grams. Leucine is the most frequently studied of the three BCAAs and several studies now have demonstrated that leucines primary mechanism of action is via activation of Mammalian Target of Rapamycin (mTOR) which is a protein that signals the body to synthesize protein. Leucine signals mTOR which in turn stimulates protein synthesis.

L-ISOLEUCINE & L-VALINE

While Leucine does appear to be more important in regards to muscle protein synthesis, isoleucine’s importance for athletes/bodybuilders pertains more to its ability to induce glucose uptake by (muscle) cells. Valine does not appear to have any unique benefits aside from helping to build proteins (as do all amino acids), but is generally grouped in because it shares the same ‘branched chain’ structure as the other two.

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 does not mean you cannot derive benefit from supplementing with BCAAs. Given the litany of studies proving the muscular/exercise-related benefits of BCAA supplementation in non-protein deficient humans, we conclude that BCAAs are among the most scientifically validated ingredients currently marketed as exercise supplements (second perhaps to creatine).

L-GLUTAMINE

Glutamine is a non-essential amino acid (your body can make it) that is required for several bodily functions, from immune health, to providing an alternative fuel-source for the brain. However, if you’re a regular at the gym (we assume you are if you’re reading this), you have probably heard of glutamine as it relates to working out. You may have also realized that glutamine, despite being one of the most widely used supplements, is also one of the most debated.

It is true that some of the alleged effects of this amino acid are not quite as grounded in science as some supplement companies might have you think, but to say that it’s completely useless is a misconception. Because glutamine is an amino acid, some people assume that it may have a muscle sparing effect. However, these claims are far from substantiated, and while we won’t dispute them, we can’t believe them.

So what is glutamine really good for? Glutamine has shown a lot of promise when it comes to fighting exercise induced immune system suppression. While it is true that our immune systems ultimately benefit from regular exercise, in the short-term, exercise actually temporarily lowers our immune defenses, thus making us more susceptible to infection during that time-frame.

This temporary compromise of the immune system has been proven to correlate with lower levels of glutamine. For this reason, it is suggested that increased uptake of glutamine may help keep the immune system strong post-exercise. In addition, lower glutamine levels have been recorded in over-trained athletes, suggesting that higher levels of glutamine may help to prevent overtraining.

CITRULLINE MALATE

The benefits of Citrulline supplementation pertain to its ability to increase ATP production, as well as buffer ammonia (generally associated with muscle fatigue). Citrulline has also been shown to increase blood arginine levels more effectively than supplemental arginine itself, making it a popular additive to nitric-oxide enhancing supplements. One thing that’s important to note is that most studies that have been done showing a positive correlation between citrulline supplementation and increased performance have used doses of atleast 6 grams. A 2008 study showed that even 15 gram dosages are safe.

However, it also showed little added benefit at that dosage. Another study that used 6 grams/day found that “The changes in muscle metabolism produced by CM treatment indicate that CM may promote aerobic energy production.” With regards to its inclusion in the Xtend formula: There is preliminary evidence to suggest Citrulline may act in a synergistic manner with Leucine by positively affecting leucine’s stimulation of mTOR.

Xtend contains 1 gram of Citrulline per serving, and while no studies exist which have tested the effects of this particular dosage, we cannot rule out some marginal benefit.

ELECTROLYTES

Electrolytes are compounds that, when placed in a solution such as water, become ionized (electrically charged). Your body requires these ions to carry electrical impulses from cell to cell (this is how your cells communicate). In other words, a proper balance of electrolytes is required to maintain healthy muscle and nerve function. Xtend contains Sodium and Potassium in levels far exceeding most sports drinks.

While it is true that exercise may increase the demand for electrolytes, we feel that their importance has been somewhat overstated through the marketing campaigns of certain sports drink manufacturers. However, while we don’t view electrolytes as much of a selling point, they are a fine addition to any supplement designed for prolonged/intense exercise (assuming they do not increase the price considerably).

THE BOTTOM LINE

Xtend is certainly one of the most comprehensive BCAA supplements we have analyzed. the formula contains 7 grams of BCAAs, as well as 2.5 grams of Glutamine and 1 gram of Citrulline. At a price of 75 cents per serving, even if Xtend just contained the 7 grams of BCAAs, it would still be a competitively priced BCAA supplement. Given that it also contains a somewhat sufficient dose of Glutamine and a marginally sufficient dose of Citrulline, we conclude that Xtend provides more ‘bang for your buck’ than most competing products.

REFERENCES
  1. Doi, Masako, et al. “Isoleucine, a blood glucose-lowering amino acid, increases glucose uptake in rat skeletal muscle in the absence of increases in AMP-activated protein kinase activity.” The Journal of nutrition 135.9 (2005): 2103-2108.
  2. Doi, Masako, et al. “Isoleucine, a potent plasma glucose-lowering amino acid, stimulates glucose uptake in C2C12 myotubes.” Biochemical and biophysical research communications 312.4 (2003): 1111-1117.
  3. Norton, Layne E., and Donald K. Layman. “Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise.” The Journal of nutrition 136.2 (2006): 533S-537S.
  4. Anthony, Joshua C., Tracy Gautsch Anthony, and Donald K. Layman. “Leucine supplementation enhances skeletal muscle recovery in rats following exercise.”The Journal of nutrition 129.6 (1999): 1102-1106.
  5. Casperson, Shanon L., et al. “Leucine supplementation chronically improves muscle protein synthesis in older adults consuming the RDA for protein.”Clinical Nutrition 31.4 (2012): 512-519.
  6. Shimomura, Yoshiharu, et al. “Nutraceutical effects of branched-chain amino acids on skeletal muscle.” The Journal of nutrition 136.2 (2006): 529S-532S.
  7. Shimomura, Yoshiharu, et al. “Exercise promotes BCAA catabolism: effects of BCAA supplementation on skeletal muscle during exercise.” The Journal of nutrition 134.6 (2004): 1583S-1587S.
  8. MacLean D.A..Graham,T.E. and B. Saltin. “Branched-chain amino acids augment ammonia metabolism while attenuating protein breakdown during exercise.” American Journal of Physiology-Endocrinology And Metabolism 267.6 (1994): E1010-E1022.
  9. Castell, Linda M., and Eric A. Newsholme. “The effects of oral glutamine supplementation on athletes after prolonged, exhaustive exercise.” Nutrition13.7 (1997): 738-742.
  10. Gleeson, M., and N. C. Bishop. “Elite athlete immunology: importance of nutrition.” International journal of sports medicine 21.Sup. 1 (2000): 44-50.
  11. Nair, K. S., R. G. Schwartz, and S. T. E. P. H. E. N. Welle. “Leucine as a regulator of whole body and skeletal muscle protein metabolism in humans.”American Journal of Physiology-Endocrinology And Metabolism 263.5 (1992): E928-E934.
  12. Alvestrand, A., et al. “Influence of leucine infusion on intracellular amino acids in humans.” European journal of clinical investigation 20.3 (1990): 293-298.
  13. Le Plénier, Servane, et al. “Effects of leucine and citrulline versus non-essential amino acids on muscle protein synthesis in fasted rat: a common activation pathway?.” Amino acids 43.3 (2012): 1171-1178.

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