Amino Acids

Amino Acids – Introduction

*Note: This section only covers the 20 naturally-occurring amino acids found in proteins

Amino acids are the building blocks of protein. Amino acids are essential for repairing tissue, especially in the muscles, bones, skin and hair. They also play a part in the function of organs, glands, tendons and arteries.

Our bodies break down the protein we eat into individual amino acids and short peptide chains, which are in turn used to create the proteins we need to function. There are nine essential amino acids (EAAs), that our bodies cannot make and therefore must be obtained through diet and 11 non-essential amino acids (NEAAs), which can be synthesised by our body.

The essential amino acids include tryptophan, lysine, methionine, histidine, phenylalanine, threonine, valine, leucine, and isoleucine. Three of these (leucine, valine and isoleucine) are called branched chain amino acids (BCAAs) due to their chemical structure. Branched chain refers to the chemical structure of the amino acids.

Branched Chain Amino Acids (BCAAs)

Three of the essential amino acids (our bodies cannot make these) leucine, valine and isoleucine are referred to as branched chain amino acids (BCAAs). BCAAs are unique among the essential amino acids in that they can be taken up directly by skeletal muscle instead of having to be metabolised by the liver.

They can serve as an efficient energy source for muscle tissue during exercise; research suggests that BCAAs can thus improve exercise capacity.[1] Research has also shown that supplementation of BCAAs before and after exercise has a beneficial effect for decreasing muscle damage and promoting muscle protein synthesis.[2]

Current products have varying ratios of BCAAs. BCAAs occur in nature (i.e. animal protein) in a 2:1:1 ratio (leucine: isoleucine: valine) and thus this appears be the most beneficial.

BCAAs & EAAs

The essential amino acids (EAAs), which our bodies cannot make, are tryptophan, lysine, methionine, phenylalanine, threonine, valine, leucine, and isoleucine. Branched chain amino acids (BCAAs) consist of only three of the essential amino acids – leucine, valine and isoleucine.

Research has shown that supplementation of BCAAs before and after exercise has a beneficial effect for decreasing exercise induced muscle damage and promoting muscle protein synthesis.[2]

EAAs contribute to protein synthesis directly, as opposed to reducing muscle breakdown. Research has shown that consuming EAAs pre-exercise has a greater protein synthesis response than when consumed post-exercise.[3]

BCAAs & Glutamine

BCAAs and glutamine taken together have shown to reduce training induced muscle tissue damage.[4] BCAAs and glutamine have added benefits when taken with protein powder. Whey protein combined with glutamine and BCAAs, in addition to resistance exercise, may help improve body composition and exercise performance.[5]

HMB

Beta-hydroxy-beta-methylbutyrate (HMB) is a natural metabolite of the essential and branched chain amino acid leucine. HMB has shown to improve strength and lean mass gains during anaerobic and aerobic training and to work as an anticatabolic to spare muscle protein and speed up recovery.[6]

In addition to speeding up recovery from high intensity exercise, HMB may assist athletes in preventing loss of lean body mass in catabolic situations such as caloric restriction.[7] When HMB is combined with creatine, the ergogenic benefits, as compared with what could otherwise be achieved by either compound independently, are significantly increased.[8]

Amino Acid Blends

Amino acids blends typically contain:

Essential Amino Acids: EAAs contribute to protein synthesis directly, as opposed to reducing muscle breakdown. Taking EAAs pre-exercise has a greater protein synthesis response than when consumed post-exercise.[3]

Branched Chain Amino Acids: Research has shown that supplementation of BCAAs (and particularly L-leucine) before and after exercise has a beneficial effect for decreasing muscle damage and promoting muscle protein synthesis.[2]

Non-Essential Amino Acids: Although the body can make the non-essential amino acids, eight of the 11 are conditional amino acids, which are usually non-essential except during times of stress (such as training or sports competition) or illness. Therefore, supplementing these during times of exercise may be beneficial.

Individual Amino Acids

Each amino acid has a specific purpose. Read below for the benefits/functions of each amino acid for athletes and gym-goers alike. Note that these are all referring to the L-form of amino acids, which are found in nature.

L-Alanine

Alanine is the most important amino acid involved in carrying nitrogen from muscle to the liver where it is converted to glucose. It is responsible for generating approximately 10% of the total energy requirements during exercise. Alanine release from muscle increases 2.5 times during prolonged exercise, so it is crucial for preserving muscle tissue and supporting blood glucose levels during prolonged exercise.[9]

L-Arginine

Assists in the production of nitric oxide (NO) resulting in vasodilation (increase in size of blood vessels and blood flow resulting in increased nutrient transport and better muscle pumps).[10] It also has beneficial effects for cardiovascular health, may help lower cholesterol, boost immune function and help heal wounds.[11]

L-Asparagine

Contributes to brain and nervous system functions.[12] Asparagine increases the resistance to fatigue during exercise and improves functioning of the liver.[13]

L-Aspartic Acid

Promotes metabolism and is used to treat fatigue and depression. Aspartic acid contributes to brain and nervous system functions as well as to the production of ATP, RNA and DNA.[14]

L-Cysteine

Provides resistance against harmful disease/infection, as it is responsible for building up white blood-cell activity. Cysteine is also necessary for the proper functioning of the skin and helps your body recover from surgery. Cysteine also helps promote building muscles, healing of severe burns, and fat burning.[15]

L-Glutamic Acid

Glutamic acid is the primary amino acid taken up into muscle during rest and exercise.[16] It is able to enhance mental clarity and alertness, as well as mood.[17]

L-Glutamine

Glutamine is a conditionally essential amino acid (the body can usually synthesise sufficient amounts of it, but in some instances of stress, the body’s demand for glutamine increases and glutamine must be obtained from the diet). It is the most abundant amino acid in human muscle and blood plasma. Glutamine has an important role in the enhancement of protein and glycogen synthesis.

Depleted glutamine levels after intense exercise or over prolonged periods of time can contribute to suppression of the immune system.

Prolonged training can deplete glutamine levels significantly for up to six hours after training, making it imperative to replace glutamine levels before, during and/or after training to enhance recovery and help avoid overtraining.[18]

Supplementing with 6-10g of glutamine before and after exercise may promote muscle mass and strength improvement.[17]

L-Glycine

Necessary for a healthy digestive system, helps convert glucose into energy. It is also essential for central nervous functioning and cellular hydration, making it useful before and during training.[19]

L-Histidine

Crucial for the production of red and white blood cells and is important for normal sexual functioning as it is converted into histamine.[20]

L-Isoleucine

Helps in increasing endurance, repairing muscle tissue and assisting the body in recovering from strenuous physical activity.[21]

L-Leucine

May well be the most anabolic and essential of all amino acids. Leucine has a superior ability to increase protein synthesis and inhibit muscle catabolism.[22]

L-Lysine

Plays a part in calcium absorption, as well as in helping building muscle protein and is used as a treatment for the Herpes Simplex Virus.[23]

L-Methionine

Assists in the breakdown of fat and reduces risk of fatty liver disease. It is also essential for the formation of healthy collagen, a protein used to form skin, nails and connective tissue.[24]

L-Phenylalanine

A precursor of tyrosine, combined with which leads to the formation of adrenaline/epinephrine. Adrenaline is a neurotransmitter converted into a similar brain chemical called noradrenaline, responsible for promoting mental alertness and memory, and for the elevation of mood and the suppression of appetite.[25]

L-Proline

Needed for the production of collagen and cartilage and helps to keep joints flexible. Endurance athletes benefit from proline as it helps to maintain muscle tissue during rigorous workouts.[26]

L-Serine

Needed for proper metabolism of fats and fatty acids, the growth of muscle, and the maintenance of a healthy immune system; also important for proper functioning of the brain and central nervous system.[27] Serine helps with the absorption of creatine that helps build and maintain muscle tissue.[28]

L-Threonine

Helps maintain proper protein balance in the body. It is important for the formation of collagen, elastin, muscle tissue and promotes proper fat metabolism in the liver.[29]

L-Tryptophan

Helps to induce relaxation and fight anxiety/depression by conversion to the neurotransmitter serotonin.[30]

L-Tyrosine

Acts as a mood elevator, can help speed up metabolism and increase cognitive function and focus. May be useful as a pre-workout energy booster as it can delay mental fatigue, enhance cognitive performance in stressful situations and improve exercise performance.[31]

L-Valine

Prevents breakdown of muscle by supplying the muscles with extra glucose for energy production during intense physical activity; also aids the removal of excess nitrogen from the liver and is able to transport nitrogen to other tissues in the body as needed.[32]

References:

[1] Mittleman, K. D., Ricci, M. R., & Bailey, S. P. (1998). Branched-chain amino acids prolong exercise during heat stress in men and women. Medicine and science in sports and exercise, 30(1), 83-91.
[2] Shimomura, Y., Murakami, T., Nakai, N., Nagasaki, M., & Harris, R. A. (2004). Exercise promotes BCAA catabolism: effects of BCAA supplementation on skeletal muscle during exercise. The Journal of nutrition, 134(6), 1583S-1587S.
[3]  Børsheim, E., Tipton, K. D., Wolf, S. E., & Wolfe, R. R. (2002). Essential amino acids and muscle protein recovery from resistance exercise. American Journal of Physiology-Endocrinology and Metabolism, 283(4), E648-E657.
[4] Sharp, C. and Pearson, D. (2010) ‘Amino Acid Supplements and Recovery from High-Intensity Resistance Training’, Journal of Strength and Conditioning Research, 24(4), 1125-1130.
[5] Colker, C.M., Swain, M.A., Fabrucini, B., Shi, Q. and Kaiman, D.S. (2000) ‘Effects of Supplemental Protein on Body Composition and Muscular Strength in Healthy Athletic Male Adults’, Current Therapeutic Research, 61(1), 19-28.
[6] Nissen, S. and Sharp, R. (2002) ‘Effect of Dietary Supplements on Lean Mass and Strength Gains with Resistance Exercise: A Meta-Analysis’, Journal of Applied Physiology (Bethesda, Md. : 1985)., 94(2), 651-659.
[7] Wilson, J.M., Fitschen, P.J., Campbell, B., Wilson, G.J., Zanchi, N., Taylor, L., Wilborn, C., Kalman, D.S., Stout, J.R., Hoffman, J.R., Ziegenfuss, T.N., Lopez, H.L., Kreider, R.B., Smith-Ryan, A.E. and Antonio, J. (2013) ‘International Society of Sports Nutrition Position Stand: Beta-Hydroxy-Beta-Methylbutyrate (HMB)’, Journal of the International Society of Sports Nutrition, 10(1), 6.
[8] Jówko, E., Ostaszewski, P., Jank, M., Sacharuk, J., Zieniewicz, A., Wilczak, J. and Nissen, S. (2001) ‘Creatine and beta-hydroxy-beta-methylbutyrate (HMB) additively increase lean body mass and muscle strength during a weight-training program’, Nutrition (Burbank, Los Angeles County, Calif.), 17, 558-66.
[9] Baldwin, K. M., Campbell, P. J., & Cooke, D. A. (1977). Glycogen, lactate, and alanine changes in muscle fiber types during graded exercise. Journal of Applied Physiology, 43(2), 288-291.
[10] Moncada, S., Palmer, R. M., & Higgs, E. A. (1989). Biosynthesis of nitric oxide from L-arginine: a pathway for the regulation of cell function and communication. Biochemical pharmacology, 38(11), 1709-1715.
[11] Sax, H. C. (1994). Arginine Stimulates Wound Healing and Immune Function in Elderly Human Beings. Journal of Parenteral and Enteral Nutrition, 18(6), 559-560.
[12] Shi, G., & Trimmer, J. S. (1999). Differential asparagine-linked glycosylation of voltage-gated K+ channels in mammalian brain and in transfected cells. The Journal of membrane biology, 168(3), 265-273.
[13] Marquezi, M. L., Roschel, H. A., dos Santos Costa, A., Sawada, L. A., & Lancha, A. H. (2003). Effect of aspartate and asparagine supplementation on fatigue determinants in intense exercise. International journal of sport nutrition and exercise metabolism, 13, 65-75.
[14] Antonio, J., Kalman, D., Stout, J.R., Greenwood, M., Willoughby, D.S. and Haff, G.G. (eds.) (2008) Essentials of Sports Nutrition and Supplements, United States: Humana Press.
[15] Childs, A., Jacobs, C., Kaminski, T., Halliwell, B., & Leeuwenburgh, C. (2001). Supplementation with vitamin C and N-acetyl-cysteine increases oxidative stress in humans after an acute muscle injury induced by eccentric exercise. Free Radical Biology and Medicine, 31(6), 745-753.
[16] Mourtzakis, M., & Graham, T. E. (2002). Glutamate ingestion and its effects at rest and during exercise in humans. Journal of Applied Physiology, 93(4), 1251-1259.
[17] A Rahn, K., S Slusher, B., & I Kaplin, A. (2012). Glutamate in CNS neurodegeneration and cognition and its regulation by GCPII inhibition. Current medicinal chemistry, 19(9), 1335-1345.
[18] Candow, D. G., Chilibeck, P. D., Burke, D. G., Davison, S. K., & Smith-Palmer, T. (2001). Effect of glutamine supplementation combined with resistance training in young adults. European journal of applied physiology, 86(2), 142-149.
[19] Vesikari, T., & Isolauri, E. (1986). Glycine supplemented oral rehydration solutions for diarrhoea. Archives of disease in childhood, 61(4), 372-376.
[20] Tabor, H. (1954). Metabolic studies on histidine, histamine, and related imidazoles. Pharmacological reviews, 6(3), 299-343.
[21] Blomstrand, E., & Newsholme, E. A. (1992). Effect of branched‐chain amino acid supplementation on the exercise‐induced change in aromatic amino acid concentration in human muscle. Acta physiologica scandinavica, 146(3), 293-298.
[22] Stipanuk, M. H. (2007). Leucine and protein synthesis: mTOR and beyond. Nutrition reviews, 65(3), 122-129.
[23] Griffith, R., Walsh, D. E., Myrmel, K., Thompson, R. W., & Behforooz, A. (1987). Success of L-lysine therapy in frequently recurrent herpes simplex infection. Dermatology, 175(4), 183-190.
[24] Wilcken, D. E., & Wilcken, B. (1976). The pathogenesis of coronary artery disease. A possible role for methionine metabolism. Journal of Clinical Investigation, 57(4), 1079.
[25] Gaddum, J. H., & Holzbauer, M. (1957). Adrenaline and noradrenaline. Vitamins & Hormones, 15, 151-203.
[26] Newsholme, E. A. (2004). Enzymes, energy and endurance. In Principles of exercise biochemistry (Vol. 46, pp. 1-35). Karger Publishers.
[27] Curtis, D. R., & Johnston, G. A. (1974). Amino acid transmitters in the mammalian central nervous system. In Ergebnisse der Physiologie Reviews of Physiology, Volume 69 (pp. 97-188). Springer Berlin Heidelberg.
[28] Wyss, M., & Kaddurah-Daouk, R. (2000). Creatine and creatinine metabolism. Physiological reviews, 80(3), 1107-1213.
[29] Eastoe, J. E. (1955). The amino acid composition of mammalian collagen and gelatin. Biochemical Journal, 61(4), 589.
[30] Biggio, G., Fadda, F., Fanni, P., Tagliamonte, A., & Gessa, G. L. (1974). Rapid depletion of serum tryptophan, brain tryptophan, serotonin and 5-hydroxyindoleacetic acid by a tryptophan-free diet. Life sciences, 14(7), 1321-1329.
[31] Chinevere, T. D., Sawyer, R. D., Creer, A. R., Conlee, R. K., & Parcell, A. C. (2002). Effects of L-tyrosine and carbohydrate ingestion on endurance exercise performance. Journal of Applied Physiology, 93(5), 1590-1597.
[32] Freund, H. R., James, J. H., & Fischer, J. E. (1981). Nitrogen-sparing mechanisms of singly administered branched-chain amino acids in the injured rat. Surgery, 90(2), 237-243.