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Amino Acid

Nitrogen-containing structural units that make up peptides and proteins. There are 20 amino acids coded by our DNA and involved in protein synthesis, of which nine are essential and must be consumed in the diet.

Our evidence-based analysis on amino acid features 28 unique references to scientific papers.

Research analysis led by Kamal Patel .
Reviewed by
Examine.com Team
Last Updated:

Amino Acid Summary

Amino Acid supplements are isolated amino acids or groups of isolated amino acids (as is the case with BCAAs) which are typically in lower doses than protein supplements and more specific.

Amino Acids are already consumed in the diet via dietary protein, but superloading specific amino acids in isolation may exert unique effects not found with food or protein supplement intake.

Amino Acids, in isolation, have a wide range of varying effects. They may either be naturally occurring amino acids (such as Taurine or Leucine) or can be slightly modified naturally occurring amino acids (as is the case with Beta-Alanine).

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Things To Know & Note

Also Known As

Amino Acids

Do Not Confuse With

Protein Supplements

Frequently Asked Questions about Amino Acid

How much protein can you eat in one sitting?
You can eat as much protein as you want in one sitting. There is a limit in how fast your body can absorb protein, but any excess protein will simply reside in your gut.

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  2. Munck LK, et al. Transport of neutral, cationic and anionic amino acids by systems B, b(o,+), X(AG), and ASC in swine small intestine. Comp Biochem Physiol A Mol Integr Physiol. (2000)
  3. Munck LK. Chloride-dependent amino acid transport in the small intestine: occurrence and significance. Biochim Biophys Acta. (1995)
  4. Dave MH, et al. Expression of heteromeric amino acid transporters along the murine intestine. J Physiol. (2004)
  5. Palacín M, et al. Molecular biology of mammalian plasma membrane amino acid transporters. Physiol Rev. (1998)
  6. Groneberg DA, et al. Intestinal peptide transport: ex vivo uptake studies and localization of peptide carrier PEPT1. Am J Physiol Gastrointest Liver Physiol. (2001)
  7. Nutritional Value of {15N}-Soy Protein Isolate Assessed from Ileal Digestibility and Postprandial Protein Utilization in Humans.
  8. Net Postprandial Utilization of {15N}-Labeled Milk Protein Nitrogen Is Influenced by Diet Composition in Humans.
  9. Luiking YC, et al. Casein and soy protein meals differentially affect whole-body and splanchnic protein metabolism in healthy humans. J Nutr. (2005)
  10. Dockray GJ. Cholecystokinin and gut-brain signalling. Regul Pept. (2009)
  11. Chandra R, Liddle RA. Cholecystokinin. Curr Opin Endocrinol Diabetes Obes. (2007)
  12. Storr M, et al. Endogenous CCK depresses contractile activity within the ascending myenteric reflex pathway of rat ileum. Neuropharmacology. (2003)
  13. Geraedts MC, et al. Direct induction of CCK and GLP-1 release from murine endocrine cells by intact dietary proteins. Mol Nutr Food Res. (2011)
  14. Deutz NE, et al. Increased intestinal amino-acid retention from the addition of carbohydrates to a meal. Clin Nutr. (1995)
  15. Ten Have GA, et al. Absorption kinetics of amino acids, peptides, and intact proteins. Int J Sport Nutr Exerc Metab. (2007)
  16. Zebrowska T, et al. Secretion of endogenous amino acids in the gastrointestinal tract and amino acid resorption in the swine. Arch Tierernahr. (1976)
  17. Contribution of rat liver and gastrointestinal tract to whole-body protein synthesis in the rat.
  18. Intestinal Mucosal Amino Acid Catabolism.
  19. Van Der Schoor SR, et al. The high metabolic cost of a functional gut. Gastroenterology. (2002)
  20. Deutz NE, Bruins MJ, Soeters PB. Infusion of soy and casein protein meals affects interorgan amino acid metabolism and urea kinetics differently in pigs. J Nutr. (1998)
  21. Soeters PB, de Jong CH, Deutz NE. The protein sparing function of the gut and the quality of food protein. Clin Nutr. (2001)
  22. Bruins MJ, Deutz NE, Soeters PB. Aspects of organ protein, amino acid and glucose metabolism in a porcine model of hypermetabolic sepsis. Clin Sci (Lond). (2003)
  23. In vivo amino acid metabolism of gut and liver during short and prolonged starvation.
  24. van Goudoever JB, et al. Intestinal amino acid metabolism in neonates. Nestle Nutr Workshop Ser Pediatr Program. (2006)
  25. Arnal MA, et al. Protein feeding pattern does not affect protein retention in young women. J Nutr. (2000)
  26. Arnal MA, et al. Protein pulse feeding improves protein retention in elderly women. Am J Clin Nutr. (1999)
  27. Soeters MR, et al. Intermittent fasting does not affect whole-body glucose, lipid, or protein metabolism. Am J Clin Nutr. (2009)
  28. Stote KS, et al. A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. Am J Clin Nutr. (2007)