Is all the protein we eat is not used for building muscles ? We eat a protein rich meal, what happens?
One of the researches conducted by Groen et al., demonstrated that after consuming 20g of protein, 40-50% of that protein is “first-pass cleared,” meaning that it’s used up by the our digestive system and liver for local metabolism, then protein synthesis and the other 50% made it into circulation. Only 11% of the total 20g protein bolus was used for muscle protein synthesis (MPS). That means that only a small percentage of what is consumed is actually used for building muscles .
So how much do we need per meal?
Well, this depends on age. Older adults develop “anabolic resistance” which means that its hard to turn on anabolic processes. Thus, older adults require more protein than younger adults to maximally stimulate MPS.
A study conducted by Stokes et al., found that young adults (22 years) can maximize MPS with 0.24 g per kg of bodyweight in a single meal whereas that number is much higher for older adults (0.60 g/kg BW). Of course, these numbers are dependent on protein quality and Bio Availability (BV) of the protein source. Protein sources with more leucine (animal proteins like whey & egg) require less protein to maximize MPS whereas lower quality sources of protein like wheat (low in leucine) require quite a bit more total protein. This data is gathered in resting adults though.
A study conducted by Witard et al., suggest that following exercise 40g has significant benefits over 20g. Our body can only absorb 30 grams of protein in a single meal has been proven untrue by many studies already. You absorb almost all of it, but only a small amount goes to MPS, but in order to maximize MPS it requires a disproportionate amount of protein compared to what is incorporated into muscle.
Thus, consuming 30-40g of protein per meal every 3-5 hours should maximize MPS & muscle growth.
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