I recall the results being equal to food/whey. Specifically, ~6g whey + 2.5g leucine (that's only ~20 cals) had an identical MPS as a typical serving of whey (can't recall the serving size but I'm assuming ~40g). It's something to think about IMO more when cutting. Maybe in the morning to stimulate MPS immediately but a few hours before you have your first real meal of the day OR intraday between long gaps in your eating.
Yes, but that is not an equal (and therefore unfair) comparison, as the
whey only group is consuming WAY more whey protein than the whey + leucine group. Furthermore, as shown in the previous study you posted, consuming leucine without additional EAA's does not increase protein synthesis to the same degree as leucine + EAAs. So, this study doesn't really apply it to the question at hand, which is "does whole food + leucine increase protein synthesis to a greater degree than equal amounts of whole food alone.
This study would be like comparing the protein synthesis rates of someone who takes 500 mg of testosterone to someone who takes only 50 mg of testosterone + 50 mg of trenbolone...and then concluding that adding trenbolone to testosterone does not result in additional increases in protein synthesis. In order for the comparison to be valid, the testosterone dose would need to be the same for both groups.
In the same way, you can't have one group consume only 6 grams of whey protein and another group consume 40 grams of whey, and then conclude that leucine supplies no additional benefit when added to whey protein. In order for a study to be relevant, we have to compare EQUAL amounts of whey, with only one of those groups supplementing with additional leucine.
There are also other studies which use equal, larger amounts of whey protein (20-40 grams, I believe) and adding leucine resulted in a greater increase in protein synthesis compared to consuming whey alone.
There are also studies comparing the protein synthesis rates of equal amounts of whey protein and whey protein hydrolysate...and the hydrolyzed whey protein group demonstrated greater increases in protein synthesis. Why? Because the leucine from the hydrolyzed whey was liberated and delivered into the bloodstream more quickly than the regular whey group. This is why adding leucine to food (or whey protein) results in a greater rate of protein synthesis--because it results in a higher concentration of leucine in the bloodstream (a critical factor in determining protein synthesis rates).
This is also why an equal amount of whey protein ALWAYS results in greater increase in protein synthesis compared to casein--because casein is digested so much more slowly (on a side note, casein is far superior at inhibiting protein breakdown, which is why every study comparing whey + casein to whey alone also showed a greater net protein gain in the whey + casein group; mother nature usually does it best).
...and don't forget, bodybuilders use a lot of other, much more slowly digesting protein sources, such as meat. The amino acids from these protein sources are liberated and delivered into the bloodstream much more slowly than free-form/peptide-bonded leucine, which is why adding leucine to whole food (especially meat) results in substantially greater increases in protein synthesis.
My main point is that adding leucine to whole food protein sources leads to a greater increase in protein synthesis...and until someone can explain to me why this additional increase in protein synthesis is irrelevant from a muscle building standpoint, I will continue to believe that supplemental leucine is beneficial.
I would like to see a study comparing larger amounts of whole food protein to an equal amount of whole food protein with additional leucine, such as 80-100 grams of meat protein. I am willing to bet that even when consuming that much meat protein, that supplementing with additional leucine will still result in greater increases in protein synthesis. Since few bodybuilders regularly consume more meat protein than that in a single sitting (most don't even eat that much per meal), it really doesn't matter if we could achieve comparable increases in protein synthesis (which I doubt) with that quantity of meat...and if it took even larger amounts of meat to achieve comparable results, it would be even more irrelevant, as no one is going to regularly consume that much meat protein in a single siting on a regular basis...and neither should they from a health standpoint (not to mention the misery associated with that type of diet).
So, even if it is just from a health and enjoyment standpoint alone, I will stick with my leucine.
As far as fat loss is concerned, yes, leucine is certainly a valuable aide for muscle maintenance when calories are low.
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