Increase Protein Synthesis Naturally – Presenting Leucine

By | October 30, 2015


The key to building muscle is to get your body to synthesize more protein than it breaks down. During intense workouts protein synthesis drops dramatically as cells try to preserve energy and keep damaged proteins from building up, followed by increased protein synthesis after working out (up to about 48hrs). However, the level of protein synthesis is not at full capacity without an adequate amount of leucine.

Amino acids play a big rule in regulating protein turnover. Of all, leucine can be considered the best amino acid for muscle growth. Leucine stimulates protein synthesis by activating mTOR (protein kinase that regulates protein synthesis) and also by activating signaling between cells, that speeds up mRNA translation initiation.  Translation initiation is important because certain steps involved in it help to mediate protein synthesis.

Study of Leucine

A study done with rat test subjects was conducted in which the rats went through endurance exercise (running). The results showed there was a 25% drop in protein synthesis by the end of a two hour run. Post workout the different groups of rats were given different meals. One group consumed a drink of sucrose and glucose, which had no effect on the protein synthesis. Another group consumed a complete meal which contained an ample amount of leucine. This second group’s rate of protein synthesis rose to normal within only an hour after the exercise.

Another study was conducted on rats that experienced decreased protein synthesis during exercise. This study’s purpose was to determine the effect of different concentrations of leucine on protein synthesis. Different amounts of leucine were given to different groups followed by the measure of protein synthesis in the gastrocnemius muscle. Results showed an increase of up to 66% from a 1x to 10x leucine concentration (1x being the concentration in the plasma of rats deprived of food). This shows that in order to maximize protein synthesis there must be an adequate dose.

How Much Leucine Should I take Daily?

Although as little as 2.5 g of leucine per day you can boost the amount of protein your body synthesizes. It is recommended for better results that you take closer to 10 g per day. For even better results divide up the dosage evenly between meals as this has shown to be beneficial for absorption.


J. Nutr. July 1, 2004
vol. 134 no. 7 1704-1710


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