β-Alanine (beta-alanine) is a naturally occurringbeta amino acid, which is anamino acid in which theamino group is attached to theβ-carbon atom (i.e. the carbon atom two carbon atoms away from thecarboxylate group) instead of the more usual α-carbon atom foralanine (α-alanine). TheIUPAC name for β-alanine is3-aminopropanoic acid. Unlike its counterpart α-alanine, β-alanine has nostereocenter.
β-Alanine is the rate-limiting precursor ofcarnosine, which is to say carnosine levels are limited by the amount of available β-alanine, not histidine.[6] Supplementation with β-alanine has been shown to increase the concentration of carnosine in muscles, decrease fatigue in athletes, and increase total muscular work done.[7][8] Simply supplementing with carnosine is not as effective as supplementing with β-alanine alone since carnosine, when taken orally, is broken down during digestion to its components, histidine and β-alanine. Hence, by weight, only about 40% of the dose is available as β-alanine.[6]
Comparison of β-alanine (right) with the more customary, chiral, α-amino acid, L-α-alanine (left)
Because β-alanine dipeptides are not incorporated into proteins, they can be stored at relatively high concentrations. Occurring at 17–25 mmol/kg (dry muscle),[9] carnosine (β-alanyl-L-histidine) is an important intramuscular buffer, constituting 10-20% of the total buffering capacity in type I and II muscle fibres. In carnosine, the pKa of the imidazolium group is 6.83, which is ideal for buffering.[10]
Even though much weaker thanglycine (and, thus, with a debated role as a physiological transmitter), β-alanine is an agonist next in activity to the cognate ligand glycine itself, forstrychnine-sensitive inhibitoryglycine receptors (GlyRs) (the agonist order: glycine ≫ β-alanine > taurine ≫ alanine,L-serine > proline).[11]
β-alanine has five known receptor sites, includingGABA-A,GABA-C a co-agonist site (with glycine) onNMDA receptors, the aforementioned GlyR site, and blockade of GAT protein-mediated glial GABA uptake, making it a putative "small molecule neurotransmitter."[12]
There is evidence that β-alanine supplementation can increase exercise and cognitive performance,[13][14][15][16] for some sporting modalities,[17] and exercises within a 0.5–10 min time frame.[18] β-alanine is converted within muscle cells intocarnosine, which acts as a buffer for thelactic acid produced during high-intensity exercises, and helps delay the onset of neuromuscular fatigue.[15][19]
Ingestion of β-alanine can causeparaesthesia, reported as a tingling sensation, in a dose-dependent fashion.[16] Aside from this, no important adverse effect of β-alanine has been reported, however, there is also no information on the effects of its long-term usage or its safety in combination with other supplements, and caution on its use has been advised.[13][14] Furthermore, many studies have failed to test for the purity of the supplements used and check for the presence of banned substances.[15]
^Weast, Robert C., ed. (1981).CRC Handbook of Chemistry and Physics (62nd ed.). Boca Raton, Florida: CRC Press. p. C-83.ISBN0-8493-0462-8..
^Wright, Margaret Robson (1969). "Arrhenius parameters for the acid hydrolysis of esters in aqueous solution. Part I. Glycine ethyl ester, β-alanine ethyl ester, acetylcholine, and methylbetaine methyl ester".Journal of the Chemical Society B: Physical Organic:707–710.doi:10.1039/J29690000707.
^Derave W, Ozdemir MS, Harris R, Pottier A, Reyngoudt H, Koppo K, Wise JA, Achten E (August 9, 2007). "Beta-alanine supplementation augments muscle carnosine content and attenuates fatigue during repeated isokinetic contraction bouts in trained sprinters".J Appl Physiol.103 (5):1736–43.doi:10.1152/japplphysiol.00397.2007.PMID17690198.S2CID6990201.
^Hill CA, Harris RC, Kim HJ, Harris BD, Sale C, Boobis LH, Kim CK, Wise JA (2007). "Influence of beta-alanine supplementation on skeletal muscle carnosine concentrations and high intensity cycling capacity".Amino Acids.32 (2):225–33.doi:10.1007/s00726-006-0364-4.PMID16868650.S2CID23988054.
^Mannion, AF; Jakeman, PM; Dunnett, M; Harris, RC; Willan, PLT (1992). "Carnosine and anserine concentrations in the quadriceps femoris muscle of healthy humans".Eur. J. Appl. Physiol.64 (1):47–50.doi:10.1007/BF00376439.PMID1735411.S2CID24590951.
^Encyclopedia of Life Sciences Amino Acid Neurotransmitters. Jeremy M Henley, 2001 John Wiley & Sons, Ltd.doi:10.1038/npg.els.0000010, Article Online Posting Date: April 19, 2001
^abQuesnele JJ, Laframboise MA, Wong JJ, Kim P, Wells GD (2014). "The effects of beta-alanine supplementation on performance: a systematic review of the literature".Int J Sport Nutr Exerc Metab (Systematic review).24 (1):14–27.doi:10.1123/ijsnem.2013-0007.PMID23918656.
