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Most savvy supplement users know that whey is the best protein for muscle recovery and growth primarily because its constituent amino acids are digested quickly and delivered to muscle tissue rapidly to stimulate muscle growth. This long held notion has come under fire with the findings of a new study published in the prestigious December 2014 issue of the Journal of Nutrition. The study compared the anabolic response of skeletal muscle to essential amino acids (EEAs) when delivered in a single bolus versus an equal amount in 4 divided doses spread over 45-min intervals.

But before launching into the details and findings of the study, it’s important to point out a few very important differences, which preclude one from applying the findings of the study to any protein and/or individual. Firstly, the study used a customised mix of essential singular free-form amino acids as opposed to popular whole proteins such as whey or casein. Secondly, the study used young healthy men (who were recreationally active) with an average age of ~20 years. And lastly, the testing was performed under resting conditions, that is to say not post-exercise, which has been the case for a number of similar studies which have compared anabolic response to proteins delivered as a single bolus or as a spread.

The group of young healthy males were split into two, with one group receiving a single 15g bolus of EAAs with the composition shown below. While the other group received the same amount, but in 4 equal divided doses of 3.75g; separated by 45-min intervals.

Essential Amino Acid

Amount

L-Histidine

1.21g

L-Isoleucine

1.73g

L-Leucine

3.59g

L-Lysine

3.07g

L-Methionine

0.95g

L-Phenylalanine

0.91g

L-Tryptophan

1.13g

L-Threonine

0.48g

L-Valine

1.86g

Total

15g

 

Throughout the ensuing 4 hours, a range of sophisticated measures were taken that provided advanced insight into the molecular and biochemical drivers of the anabolic response of skeletal muscle in the two groups. These included the total level of EAAs as well as leucine, plus the level of insulin. Another innovative measure was that of microvascular blood volume in the thigh and changes in leg blood flow. Lastly, the subjects had to endure a number of muscle biopsies (very painful procedures that excise a small piece of muscle using a specialised needle) to measure the different regulatory proteins associated with muscle protein synthesis.

Without going into the nitty gritty of it all, the main finding of the study when all the data was pooled together from the two groups was that the way in which EAAs were administered did not influence the anabolic response of muscle tissue in the young men at rest. That is to say that delivering EAAs in a single bolus or divided doses does not seem to be a key factor in maximising the protein synthesis response of muscle tissue. Put another way, this study showed that the level of amino acids in blood do not seem to be the key driver of anabolism when young individuals (at rest) consume the same total quantity of EAAs, albeit with a different delivery profile. Instead, this study suggests that muscles reach a ‘full’ state once a certain threshold dose of EAAs have been administered.

One needs to be careful not to apply the findings of this study to all mixes of essential amino acids. It’s worth noting the relatively high percentage of leucine (i.e. 24%) in the EAA mix used in this study. It’s possible that EAA mixtures with lower levels of leucine may not have yielded the same result. It’s also important to mention that the findings cannot be applied to the elderly, for whom it has already been established they require higher levels of protein and leucine to overcome their documented anabolic resistance.

As mentioned at the outset, this study used a mix of EAAs and as such, one cannot say whether the same results would be evident if a whey protein or whey protein hydrolysate was used. Lastly, its possible that had the subject exercise prior to ingesting EAAs, the results may have been different. It is well established that resistance exercise provides a strong stimulus to muscle protein synthesis, which persists for up to 24 hours. Nonetheless, the study serves as a timely reminder of the many holes in our knowledge concerning the interaction of protein/EAAs and muslce protein synthesis.

 

Mitchell WK, et al. A dose- rather than delivery profile-dependent mechanism regulates the “muscle-full’ effect in response to oral essential amino acid intake in young men. The Journal of Nutrition. 2015, February 1st.

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