Thread by @nick_krontiris

The optimal protein intake for muscle protein synthesis seems to be around ~160g per day, a thread:

Lemon et al, 2017

doi.org/10.3945/jn.116…

The breakpoint here was 1.7g/kg of protein per day (The upper 95% CI of the breakpoint was at 2.2g and the lower CI was 1.2g)

Roberts et al, 2018

doi.org/10.3389/fnut.2…

No benefit from protein intakes higher than 1.6g/kg per day

Morton et al, 2018

dx.doi.org/10.1136/bjspor…

Breakpoint at 1.62g/kg per day

20g of protein gives a near-maximal increase in MPS after resistance training. Going up further to 40g will result in even a further, although slight, increase in MPS

pubmed.ncbi.nlm.nih.gov/19056590/
pubmed.ncbi.nlm.nih.gov/24257722/

Protein quality matters. Leucine content of the meal matters (a meal should provide ~3-4g of leucine for MPS), and the EAAs it provides matter.

Of the protein ingested, approximately 50% will be extracted by splanchnic tissues before entering peripheral circulation and only ~10% of the ingested protein will be utilized for skeletal muscle protein synthesis while the rest will be catabolized.

doi.org/10.1371/journa…

In the words of a paper I recently read

"the activation of mTORC1 is only one of several important components required for the complete synthesis of new proteins, including the availability of precursor AAs"

"If you bought a sports car, you can drive at 100 mph as long as you have gasoline in the tank. However, you cannot go without gasoline (i.e., no AAs) despite having a powerful engine (i.e., a fully activated mTORC1)"

Engine being leucine

doi.org/10.4235/agmr.2…

Therefore the bioavailability of the food that provides you said protein matters too.

Bear in mind that in most studies, the subjects are omnivores so you expect ~60:40 animal:plant based protein intake.

Something that is corraborated by this study:

pubmed.ncbi.nlm.nih.gov/27710150/

All that said, Gwin et al 2020 sheds some doubt on the ~1.6g/kg per day, as while in a caloric deficit, an extra 23.3g of EEAs resulted in greater whole body protein balance in subjects that were already consuming 1.6g/kg of protein per day than the group that consumed 7.8g/kg

Study here:

https://twitter.com/DrMyohead/status/1291039444380737537

Now, note that whole-body protein metabolism measures the synthesis of all proteins in the body, which means this may not necessarily reflect gainz.