LEUCINE IS BETTER THAN ALL OTHER AMNIO ACIDS COMBINED FOR MUSCLE GROWTH

To maximize muscle hypertrophy during weight training, one must consume about 1.0-1.5 g/kg of protein.  Researchers have tested the effects of timing of protein supplement ingestion on various physical changes in weightlifters. In general, protein supplementation pre- and post-workout increases physical performance, training session recovery, lean body mass, muscle hypertrophy, and strength. Specific gains, differ however based on protein type and amounts. Studies on timing of consumption of milk have indicated that fat-free milk post-workout was effective in promoting increases in lean body mass, strength, muscle hypertrophy and decreases in body fat. The leucine content of a protein source has an impact on protein synthesis, and affects muscle hypertrophy.  A combination of a fast-acting carbohydrate source such as maltodextrin or glucose should be consumed with the protein source, as leucine cannot modulate protein synthesis as effectively without the presence of insulin. Such a supplement post-workout would be most effective in increasing muscle protein synthesis, resulting in greater muscle hypertrophy and strength.

Anyone involved in weight training would benefit by knowing ideal nutritional intake needed to maximize muscle growth and strength.  Multiple studies have indicated the amino acid leucine to be the sole stimulator of protein synthesis.  A study by Dreyer et al. confirmed this by comparing post-workout consumption of either no beverage or a leucine enhanced beverage.  Leucine alone appears to as effective in stimulating protein synthesis as when, if not better, then when all other branched chain amino acids (BCAAs) are consumed.

Numerous protein sources are available and generally come come in diary- or soy-based sources.  Two important qualities of these two sources are biological value (BV) and protein digestibility corrected amino acid score (PDCAAS).  Biological value is how efficiently protein leads to protein synthesis once absorbed with a maximum value of 100.  PDCAAS score is a maximum of 1.0, and is based on the protein’s completeness of their essential amino acid content. 

Cow’s milk generally contains 80% casein and 20% whey, with a BV score of 91 and a PDCAAS of 1.0; indicating its readily absorbed and promotes protein synthesis while providing all essential amino acids.  Casein by itself has a BV of 77, and whey has a better absorption and utilization with a BV of 104.  Both have a PDCAAS of 1.0.  Casein is what milk gets its milky white color from.  Soy protein has a PDCAAS of 1.0, containing all the essential amino acids, but its BV is 74, making it less bioavailable than milk.  Multiple studies have supported consumption of either protein source increases strength and lean body mass, with decreased body fat in both woman and men.  Studies have also shown that protein divided pre/post-workout (15g each) had superior results compared to all protein taken post-workout.  The best time to take protein is 45-90 minutes pre- and post-workout. 



Because leucine is the greatest amino acid in promoting muscle growth, it should be consumed during post-workout consumption.  3-4g of leucine content per serving needs to be consumed for maximal muscle growth.  Leucine potently activates the mammalian target of rapamycin kinase that regulates cell growth.  Infusion of leucine into the rat brain has been shown to decrease food intake and body weight via activation of the mTOR pathway.  Leucine is an essential amino acid, and so the human body cannot make it on its own.  The highest concentration of leucine is seen in soybeans (2.97 / 100g) compared to cow’s milk (0.27 / 100g).  It is very difficult to find a protein product that offers 3-4g of leucine per serving.  Examples of great leucine supplementation are listed below.