Muscle protein synthesisMPS

Muscle protein synthesis (MPS) is the process by which the body builds new muscle protein. Muscle is not a static lump: it is constantly being broken down and rebuilt, and net growth happens only when synthesis outpaces breakdown over weeks and months.

Two things raise it reliably. A hard resistance training session raises it for roughly a day or two afterwards, and eating protein raises it in a sharp, short spike. The two together produce a bigger response than either alone, which is the entire mechanistic case for eating protein around training.

The response saturates, which is the practically useful bit. Muscle protein synthesis is maximised in young adults by roughly 20 to 25 g of high quality protein in a sitting, and the ISSN review of per meal distribution puts a sensible upper target near 0.4 g per kg of bodyweight per meal across at least four meals. Eating 90 g in one go does not build more muscle than 30 g does; it just costs more.

Daily total still dominates. A meta-analysis of 49 trials in 1,863 people found protein supplementation improved gains in fat free mass and strength during training, and that the benefit disappeared once total intake passed about 1.6 g per kg a day. Distribution is the fine tuning; the total is the lever.

Beware of reading it as a scoreboard. MPS is measured over hours in a laboratory, and short term spikes predict long term growth loosely at best. Studies that produce a bigger acute MPS response do not always produce more muscle over three months, so treat any supplement sold on an acute MPS graph with the scepticism that gap deserves.

Age changes the arithmetic. Older muscle responds less to a given dose of protein, a phenomenon called anabolic resistance, which is why the PROT-AGE recommendations for healthy older adults start at 1.0 to 1.2 g per kg a day rather than the general population reference intake. More protein and more resistance training are the two levers that still work.

In practice: hit the daily total first, spread it across three or four meals with a decent serving in each, and keep training the muscle. Our macro calculator sets the target from your bodyweight and goal.

Sources

• Schoenfeld BJ, Aragon AA. How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. J Int Soc Sports Nutr 2018;15:10
• Morton RW, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength. Br J Sports Med 2018;52:376-384
• Bauer J, et al. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. J Am Med Dir Assoc 2013;14:542-559