Leucine
is an essential branch chain amino acid (BCAA) and has become a popular
nutritional supplement amongst athletes in strength and power based sports as a
pre and post exercise (Mero 1999, Pitkanen et. al. 2003, Crowe et. al. 2006). It
is also commonly consumed amongst the general population in protein-based
products such as soybeans, beef and peanuts as it is essential in all diets.
Positive
Leucine
has been show to have to following benefits when used in conjunction with
resistance training as it;
- Decreases training induced muscle damage through protein metabolism regulation which has shown to positively impact long term training and performance outcomes by limiting muscle degradation when consumed before after and/or during exercise (Mero 1999, Nair et. al. 1992).
- Improves speed and quality of recovery as well as reduce the time to exhaustion and rate of perceived exhaustion by stimulating protein synthesis in the skeletal muscle (Mero 1999, Pitkanen et. al. 2003, Crowe et. al. 2006, Laymen 2002).
- Significantly increases relative power and work in trained muscles (Crowe et. al. 2006, Blomstrand et. al. 1991 and 1997).
- Portions throughout a training session has shown to counteract the lose of Leucine plasma levels in the body, which has been measured at approximately 30% per training session (Mero 1999).
- Improves mental and physical performances (Mero 1999)
- Acts as a source of muscle energy, accounting for 3 – 4 % of energy use at rest and 1% during exercise (Mero 1999, Young and Bier 1987).
Negative
Long-term
excessive use of Leucine can result in a number of adverse outcomes/no effect
- Maple Syrup Urine Disease although is a rare genetic disease found predominantly in infants, where amino acids cannot be broken down in the body the use of Leucine will result in blood toxicity and lead to a number of adverse symptoms such as Food avoidance/feeding difficulties, urine smelling like maple syrup, vomiting and coma. (Medline Plus 2013)
- Excessive Leucine within the body has also been linked to Pellagra a disease caused by the body not receiving enough niacin or tryptophan, however the reason why is still unknown. Symptoms include diarrhea, dermatitis, dementia and death in extreme cases.
- Over activity of the liver due to excessive supplementation over a long period of time, without adequate use of the Leucine consumed (Mero 1999)
- Adverse affects on cellular growth causing a decrease in food consumption thus body weight and bodies ability to maintain muscle fibre size (Mero 1999)
- Acute doses of Leucine prior to exercise had no effect on power based assessment results (Pitkanen et. al. 2003)
Personal opinion of Leucine use
The
use of Leucine when undergoing resistance training has been met with mixed
research Godard et. al (2002) and Pitkanen et. al. (2003) who reported that
Leucine had limited effect on strength and power performances, however Crowe
et. al. (2006), Layman (2002) that reported that Leucine supplementation does
increase performance while also decreasing training induced muscle damage
Based
on these finding it has been concluded that the use of Leucine as a ergogenic
aid for resistance training is of beneficial pre, post and can also be consumed
during training in order to improve an athletes ability to train harder for
long (maintaining power output), recover quicker and increasing muscle size and
efficiency.
However
the use of the supplement should cease until a full medical check is taken
before using large or increased quantities of the amino acid and that the
consumption levels need to be prescribed in consultation with a sports
nutritionist to minimise any potential long term toxicity or cellular growth
risks due to research by Mero (1999), Pitkanen et. al. (2003) and Golgan (1993)
stating a significant increase to recommended dietary intake is needed in order
to be effective in the general population and that athletes participating in
resistance training need even more,
however how much more is not specific.
Finally as long as the consumption of Leucine
is not through injections (parental use) is deemed legal outside of and during
competition (ASADA 2013)
Reference
List
Journal
Articles
Blomstrand, E., Hassman, P.,
Ekblom, B., Newsholme, E. (1991). Administration of branched-chain amino acids
during sustained exercise-effects on performance and on plasma concentration of
some amino acids. European Journal of Applied Physiology and Occupational
Physiology, 63, 83 – 88.
Blomstrand, E., Hassman, P.,
Ekblom, B., Newsholme, E. (1997). Influence of ingesting a solution of branched
chain amino acids on perceived exertion during exercise. Acta Physiologica
Scandinavica, 159, 41 – 49.
Crowe, M., Weatherson, J.,
Bowden, B. (2006). Effects of dietary Leucine supplementation on exercise
performance. European Journal of Applied Physiology 97, 664 – 672.
Godard, M., Williamson, D.,
Trappe, S. (2002) Oral amino acid provision does not affect muscle strength or
size gains in older men. Medicine & Science in Sports & Exercise, 34,
1126 – 1131.
Layman, D. (2002) Role of
Leucine in protein metabolism during exercise and recovery. Canadian Journal of
Applied Physiology, 27, 646 – 663.
Mero, A. (1999). Leucine
Supplementation and Intensive Training. Journal of Sports Medicine, 27 (6),
347-358.
Nair, K., Schwartz, R., Welle,
S. (1992). Leucine as a regulator of
whole body and skeletal muscle protein metabolism in human. Journal of
Physiology, 263, 928 – 934.
Pitkanen, H., Oja, S., Rusko,
H., Nummela, A., Komi, P., Saransaari, P., Takala, T., Mero, A. (2003). Leucine
supplementation does not enhance acute strength or running performance but
effects serum amino acid concentration. Amino Acids, 25, 85 – 94.
Young, V., Bier, D. (1987). A
kinetic approach to the determination of human of amino acid requirements. Nutrition Review,
45, 289 – 298.
Books
Golgan, M. (1993) Optimum
sports nutrition. NY: Advanced Research Press.
Websites
Australian Sports Anti-Doping
Authority. (2013). MRT Product/Substance Details. [Version 1 – 27 October].
Retrieved from
https://checksubstances.asada.gov.au/details.aspx?prodid=&subid=2625&resultid=6638B93E-F2D9-4F97-92CE-87A8EAC8A65C
Medline Plus. (2013). Maple
syrup urine disease. [Version 1 22March http://www.nlm.nih.gov/medlineplus/ency/article/000373.htm
