What are amino acids?

Proteinogenic amino acids are the building blocks of proteins. The body puts them together in specific sequences depending on their destined function. 20% of the human body is made up of protein. Protein plays a crucial role in almost all biological processes: digestion, building muscle, immune system, hormone production among others.

There are 21 different proteinogenic amino acids. The body can synthesise 12 of these from scratch – these are known as non-essential and conditional amino acids. The other nine must be obtained through our diets – these are the essential amino acids (EAAs). Amongst these essential amino acids are branched chain amino acids (BCAAs) which are responsible for muscle protein synthesis. They are called branched-chain amino acids because their chemical makeup has a unique branched structure.

The nine amino acids humans cannot synthesise (BCAAs in bold):

    • Phenylalanine
    • Threonine
    • Tryptophan
    • Methionine
    • Leucine
    • Isoleucine
    • Valine
    • Lysine
    • Histidine

How EAAs work in the body

Nitrogen is a fundamental component of amino acids. Therefore, measuring nitrogen inputs and losses can be used to study protein metabolism.

  • When nitrogen intake is more than nitrogen excretion, then you have an anabolic (build up) state in the body.
  • When nitrogen intake is less than nitrogen excretion, then you have a catabolic (break down) state in the body.

Increased concentrations of EEAs activates nutrient sensing mechanisms, which modulate the P70-S6 Kinase 1 pathway including mTORC1 responsible for muscle protein synthesis.

This pathway is typically activated by physical exercise and the ingestion of branched-chain amino acids – specifically Leucine. The mTORC1 pathway can also be induced by IGF-1 expression and the other two BCAAs, but are much weaker than leucine in doing so.

Adequate consumption of EAA Increases lean body mass (LBM), muscle protein synthesis, and Insulin-Like Growth Factor-I (a hormone with anabolic effects in adults) expression. If you fail to consume sufficient amounts of EAAS, your body will not be able to optimise the nutrients from protein sources that are consumed. This will prevent you from synthesising new muscle tissue to the highest possible degree.

As a rule of thumb, getting five grams of Leucine post-workout along with 20-25 grams of protein is the most effective dose when it comes to building muscle.

(Pasiakos, 2012; Holz and Blenis, 2005; Brook et al., 2015).

When to take EEAs for optimal results

As previously mentioned, Leucine is the essential BCAA that stimulates muscle protein synthesis when at least 5g are ingested. With this information, you would assume a BCAA or even an isolated leucine supplement source is optimal. You would be wrong.

Leucine may stimulate muscle protein synthesis, but that is only putting the key into the ignition. There must also be a source of energy to make or repair muscle tissue. This is where the EEAs come into play.

For example, the average 20-25g scoop of whey protein is comprised of roughly 10% leucine – meaning you ingest 2-2.5g of leucine per scoop of whey protein. Whey is digested at a rate of about 10g/hr. Therefore, if you ingest 50g of whey, you also ingest the required 5g of leucine as well as 5 hours of potential muscle protein synthesis.

Regarding maximising muscle protein synthesis, what this tells us is us is that spacing meals out about 4 to 5 hours apart, with 40-50g of protein and supplementing EEAs during and between meals is the most effective method. This is due to the steady supply of leucine and other essential amino acids responsible for anabolism. This is especially effective for those following a plant-based diet.

If you are still not getting it: the take-home point of this is that taking BCAAs or leucine alone is excellent for initiating muscle protein synthesis, however, is redundant after that. A supply of all 9 essential amino acids is required for extended muscle protein synthesis and anabolism if you wish to achieve maximum results.

(Bohe, J. 2001; Norton, L.E., et al. 2007;  Katsanos, C.S., et al. 2006;  Anthony, J. et al. 2000).

Other effective times to take EEAs

Consuming EAAs before training can increase uptake into muscle tissue). Benefits include:

  1. EAA supplementation may lower lactate levels after resistance training and improve muscular oxidation.
  2. EAAs may increase growth hormone (GH) circulation, which may be related to the anabolic mechanisms causing muscle growth.
  3. EAA supplementation may decrease serum concentrations of the intramuscular enzymes: creatine kinase, and lactate dehydrogenase following prolonged exercise. This can decrease muscle damage and improve recovery.

During long bouts of training supplementing EAAs can be an efficient method to increase the efficiency of nitrogen supply and storage in the muscle ensuring minimal muscle wastage occurs. This may decrease serum concentrations of the intramuscular enzymes creatine kinase and lactate dehydrogenase following prolonged exercise. This can decrease muscle damage and improve recovery.

(Mittleman, K.D., et al. 1998; De Palo, E.F., et al. 2001; Coombes, J.S, McNaughton, L.R, 2000).

Other benefits of EAA supplementation

  • In a 2009 study, EAA taken twice daily between meals improved LBM and basal muscle protein synthesis in older individuals. The acute anabolic response to EAA supplementation is maintained over time and can improve LBM in elderly females. (Dillon et al., 2009).
  • Supplementation with EAAs has also yielded positive results as an approach for a moderate reduction in plasma Triglycerides. High triglycerides are often a sign of other conditions that increase the risk of heart disease and stroke as well, including obesity and metabolic syndrome. (Marquis et al., 2017).
  • EEA supplements can improve focus in the gym by inhibiting tryptophan (an amino acid) from converting to serotonin in the brain which causes fatigue and lethargy.
  • Muscle is an important site of BCAA activity. There is an increased cell concentration and breakdown of BCAAs in muscle tissue. BCAAs are continuously supplied from the liver and other internal organs to skeletal muscle so that the BCAAs can assist in maintaining blood sugar levels. BCAAs may be responsible for up to 40% of blood sugar production during exercise. (Ahlborg G et al. 1974; Layman DK 2003).

References:

Ahlborg G, et al. Substrate turnover during prolonged exercise in man. J Clin Invest 1974;53:1080-1090.

Anthony, J. C., Anthony, T. G., Kimball, S. R., Vary, T. C., & Jefferson, L. S. (2000). Orally administered leucine stimulates protein synthesis in skeletal muscle of post absorptive rats in association with increased eIF4F formation. The Journal of Nutrition, 130(2), 139-145.

Bohe, J. (2001). Latency and duration of stimulation of human muscle protein synthesis during continuous infusion of amino acids, J Physiol Volume 532, Number 2, 575-579.

Brook, M., Wilkinson, D., Phillips, B., Perez-Schindler, J., Philp, A., Smith, K. and Atherton, P. (2015). Skeletal muscle homeostasis and plasticity in youth and ageing: impact of nutrition and exercise. Acta Physiologica, 216(1), pp.15-41.

Coombes JS, McNaughton LR. Effects of branched-chain amino acid supplementation on serum creatine kinase and lactate dehydrogenase after prolonged exercise. J Sports Med Phys Fitness 2000;40:240-246.

De Palo EF, et al. Plasma lactate, GH and GH-binding protein levels in exercise following BCAA supplementation in athletes. Amino Acids 2001;20:1-11.

Dillon, E., Sheffield-Moore, M., Paddon-Jones, D., Gilkison, C., Sanford, A., Casperson, S., Jiang, J., Chinkes, D. and Urban, R. (2009). Amino Acid Supplementation Increases Lean Body Mass, Basal Muscle Protein Synthesis, and Insulin-Like Growth Factor-I Expression in Older Women. The Journal of Clinical Endocrinology & Metabolism, 94(5), pp.1630-1637.

Holz, M. and Blenis, J. (2005). Identification of S6 Kinase 1 as a Novel Mammalian Target of Rapamycin (mTOR)-phosphorylating Kinase. Journal of Biological Chemistry, 280(28), pp.26089-26093.

Katsanos CS, Kobayashi H, Sheffield-Moore M, Aarsland A, Wolfe RR. (2006) A high proportion of leucine is required for optimal stimulation of the rate of muscle protein synthesis by essential amino acids in the elderly. Am J Physiol Endocrinol Metab. 2006 Aug;291(2):E381-7.

Layman DK. The role of leucine in weight loss diets and glucose homeostasis. J Nutr 2003;133:261S-267S.

Marquis, B., Hurren, N., Carvalho, E., Kim, I., Schutzler, S., Azhar, G., Wolfe, R. and Børsheim, E. (2017). Skeletal Muscle Acute and Chronic Metabolic Response to Essential Amino Acid Supplementation in Hypertriglyceridemic Older Adults. Current Developments in Nutrition, 1(11), p.e002071.

Mittleman KD, et al. Branched chain amino acids prolong exercise during heat stress in men and women. Med Sci Sports Exerc 1998;30:83-91.

Norton LE, Layman DK, Garlick PJ, Brana D, Anthony TG, Zhao L, Devkota S, Walker DA. (2007). Translational controls of skeletal muscle protein synthesis are delayed and prolonged associated with ingestion of a complete meal. Experimental Biology meeting abstracts [on CD-ROM], Abstract #694.6

Pasiakos, S. (2012). Exercise and Amino Acid Anabolic Cell Signaling and the Regulation of Skeletal Muscle Mass. Nutrients, 4(7), pp.740-758.