I’ve seen a lot of results regarding net protein synthesis with respect to amino acid profiles, and in general, higher concentrations of specific amino acids were tied to greater synthesis. (Especially Leucine through mTOR.) Is this misleading somehow?
Yeah, leucine is a bit of a hot topic among the intermittent fasting crowd because of its apparent ability to arrest fasting-induced autophagy. Some amount is clearly critical for anabolic signaling, but the evidence I've seen indicates that extra dietary leucine (in excess of typical consumption) has no effect on actual muscle synthesis [1].
There is compelling evidence supporting supplementation of some conditionally essential amino acids such as carnosine (perhaps vis-a-vis beta-alanine) and glutamine. There's also increasing interest in restriction of specific amino acids, namely methionine, for anti-aging and cancer treatment.
But all this talk of supplementation and restriction, outside of what occurs naturally in foods, stands in opposition to the dietary notion of protein completeness. My hope is that it will eventually lead to more appropriate and flexible measures of dietary protein quality.
