How much protein can you utilise at once? And is it okay to eat all of your protein in one sitting?
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Common misconception: there is a “limit” to how much protein can be absorbed by the body.
The term absorption refers to the nutrients that can be absorbed from the gut into the blood stream and by this definition, it is virtually unlimited!
So what do people mean when they refer to this idea of “protein absorption limits”?
Likely, how much protein can maximally stimulate muscle protein synthesis (MPS). This is known as the muscle full concept – that anything above a certain quantity of protein consumed will either be utilised to generate energy (oxidised) or changed into another substance for the body to use.
Studies indicate that if you infuse a muscle with amino acids (AAs- the building blocks of protein), there is a short delay (approx. 45 mins) before MPS approximately trebles (between 30-120 mins) after which it returns to baseline, despite elevated availability of AAs (1,2).
What quantity of protein maximises MPS?
Initial research indicated that 20g of whey protein maximised MPS in men following resistance exercise (3). However a more recent study showed that a 40g dose of whey protein increased the rate of MPS by 20% versus a dose of 20g of whey (4).
However since building muscle is a balance between MPS and muscle protein breakdown (MPB), we must also consider the impact of protein quantity on MPB. A comparison of the consumption of either 40g or 70g beef protein showed the higher protein intake to promote a significantly greater whole-body anabolic response, primarily due to a reduction in MPB (5).
However, a limitation of this study is that it measured protein balance at the whole-body level. The capacity to assimilate dietary protein at a whole body level is substantially greater than for muscle tissue and it would seem more likely that these AA would have been utilised for tissues such as the gut.
What does the research say on protein distribution and mass gains?
Although there is research to indicate a maximum quantity of protein can be utilised in one window of feeding to maximise MPS, research to show how this translates into lean muscle mass change is limited.
Research that challenge the notion that protein distribution does not matter:
However, there are several limitations to this research. These include, the short durations over which the studies were conducted, the use of BIA (bioelectrical impedance analysis) to measure body composition and importantly comparisons of overall low total protein intake.
Since total protein intake is the most important factor for maximising mass gains, comparing protein distributions where individuals are meeting their optimal protein intake would be necessary in order to draw meaningful conclusions.
Studies indicating that protein distribution does matter:
So does protein distribution matter?
Limitations to utilising current research on protein distribution are the comparison of different amounts of protein distributed per day and total protein intakes, over differing time frames. Additionally, short-term conclusions are not necessarily translatable into the long-term.
However, studies do consistently show that the dosing ceilings for maximising MPS may be between 0.4 – 0.6 g/kg (3,4), indicating that distributing protein is pertinent when maximising MPS (it should be noted that this is based on a rapidly digesting protein source).
Additionally studies support distributing protein into 4-5 meals per day for athletes, concluding that this feeding frequency may be most favourable and metabolically efficient when the goal is to maximise mass gains and minimise the oxidation of AA (10,11).
How much protein per meal?
Prioritise evenly distributing total protein intake between number of meals per day to maximise muscle strength and size. A recent meta-analysis of studies indicated that regardless of being in an energy balance or energy excess, 1.6-2.4 g/ kg/day may be beneficial (12).
When having 4 meals per day 0.4–0.6 g/kg/meal would facilitate meeting protein requirements of 1.6-2.4 g/kg/day (12).
Whether you shoot for a slightly higher or lower amount may be decided based on your individual needs, protein source and how well you digest the protein – go for the lower end of the scale if you are overweight and higher end if you are leaner and train more.
Whilst higher protein consumption may result in AA oxidation, research indicates that additional protein may be utilised for tissue building purposes.
Other factors that may impact MPS rates:
Protein source: you want the optimal ratio of EAAs (essential amino acids) and leucine – animal sources of protein such as whey or egg have these.
Quality of protein: a protein that has the optimal ratio of EAAs and leucine and is easily digested may have very different effects to one that does not. Mixed protein blends, with lower quantities of EAAs and leucine, which are less well digested, generally result in a suboptimal MPS response compared to an equal amount of whey protein (15).
Therefore when consuming plant based proteins you will require a larger quantity to have the same impact.
Whether the food is whole: whole food sources may have a more anabolic effect. For example, whole milk may be more anabolic than skimmed milk and whole eggs more so than egg white (16,17).
Being in a negative energy balance: during chronic dieting, or due to low energy availability (being very lean or as an athlete) the protein intake required to maximise MPS may be slightly greater (19,20).
Shooting for the higher intake of protein per meal (0.5 g/kg/meal) is recommended. A higher protein intake is also beneficial for individuals needing to cut or lose weight due to the benefits of feeling more full and post-prandial thermogenesis (increased energy expenditure!).
Age: research indicates that for individuals >70 years, the ingestion of 40g of whey enhanced post-exercise MPS to a greater extent than 20g of whey (14).
Prioritising hitting your daily protein intake is the most important nutrition factor for maximising your gains: so hitting 1.6-2.4 g/kg protein/bodyweight per day. This is your priority.
Distributing protein between 4 meals may be optimal: with research indicating a cap of 0.4-0.5 g/kg of protein to maximise MPS.
Consider your protein source: and adjust the quantity based on the quality and how well you digest it. If you are consuming plant based protein it is likely that you will require a higher total intake. Additionally a whole-foods source may be slower digested than a whey protein so consider this with timing around your training.
What are your thoughts on protein distribution? Is it something that you prioritise? Would love to hear in the comments below!