While many other research papers have been devoted to the effect of resistance training and amino acid intake on protein synthesis following exercise, hardly any research had been done on the effect of protein synthesis from a whole food source, such as milk.
This study was one of the first to examine the impact that different types of milk had on markers of protein synthesis and amino acid uptake.1
The main reason the authors wanted to perform this study was to see if there would be any difference between consuming skim milk and whole milk after resistance training. This would better inform weight lifters on which type of milk they should prefer after a resistance training session in order to maximize muscle growth.
Volunteers of this study were randomly placed into 1 of 3 groups, which were provided different types and amounts of milk, 1 hour prior to completing a leg-based resistance exercise routine.
Thus, the research compared drinks that were matched by weight and protein (Skim milk vs. whole milk) and compared drinks that were matched by calories (whole milk vs. isocaloric skim milk). This was done in order to know whether whole milk is more advantageous than skim milk just because whole milk has more calories or because of something special in the whole milk, like the greater amount of fat.
In order to increase the calories in the isocaloric skim milk, the researchers added sucrose, or table sugar, to skim milk.
Following the ingestion of these drinks, the researchers measured net muscle protein balance, which was determined by measuring amino acid balance (specifically threonine and phenylalanine as markers) across the leg.
Wait, What's Protein Balance?
Throughout the day, you have a constant breakdown and build up of various proteins in the body, including those which make up skeletal muscle. It's postulated that as long as protein "build up" is greater than protein "breakdown," muscle growth can occur.
Protein balance measurements would simply be to determine which of the two sides (breakdown / build up) happening to a great extent. (Balance would be an equal amount of protein breakdown to protein build up.
Despite low significance, based on the results, it's safe to extrapolate that if the sample size was larger, the effect observed with whole milk would likely be significant meaning superior for growth. Overall, the researchers conclude that these results suggest whole milk may allow for increased utilization of amino acids need for protein synthesis, over that of skim or low fat, milk variants.
Total Protein Intake Was Low
The amount of protein necessary to maximize muscle protein synthesis is somewhere between 20 – 40 g, depending on the age and weight of the individual. The amount of protein used in this study was between 8 – 14.5 g. Thus, the significance of the results may be diminished if enough protein was used to maximize protein synthesis. Put another way, these results might not matter if you are downing 40g of protein after you work out anyway. However, we do not know this for certain.
Results Here Might Not Represent Long-Term Muscle Growth
Previous studies have shown that changes in muscle protein synthesis do not necessarily correlate with long term changes in muscle growth.2 That is, just because someone measures as having high rates of protein synthesis repeatedly does not necessarily mean that they will gain more muscle than someone who repeatedly measures with lower protein synthesis.
This study didn’t actually even measure the protein synthetic response, but instead measured amino acid uptake, meaning that what they measured is actually even one step farther away from practicality and long term predictive power.
Why this should matter to you
While the study is limited in its statistical power and relevance, there are some key takeaway points:
Overall, this should matter because it gives us an idea of how to best optimize the protein synthetic response to exercise, which is the current leading theory behind muscle growth. If you could have a better potential to grow muscle using whole milk vs. skim, this is important and valuable information.
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