How much protein per serving?

The amount of protein per meal is a central issue in sports nutrition. Many believe that massively increasing intake within the same meal is productive. This reasoning omits the constraints imposed by human physiology: beyond a certain threshold, the excess is no longer directed towards muscle protein synthesis (MPS) but towards the irreversible oxidation of amino acids (Witard et al., 2014).

It is established that physical activity increases nitrogen requirements, but anabolic capacities are limited by the phenomenon of the "Muscle Full Effect". While proteins activate anabolic signaling via the mTOR pathway, an excess becomes inoperative for tissue construction, saturating the storage capacity of the free amino acid pool.

Digestive and enzymatic capacity

The absorption kinetics are limited by the availability of intestinal transporters and the activity of proteases (pepsin, trypsin, chymotrypsin). An excessive protein load (e.g., >50g in one serving) can saturate these mechanisms, leading to residual colonic protein fermentation. This can disrupt the microbiome and increase the production of secondary metabolites such as indole or p-cresol. To optimize assimilation, it is advisable to divide the intake into moderate doses of 20 to 35g.

Hyperaminoacidemia and cellular plateauing

A very high plasma level of amino acids does not linearly increase protein synthesis. There is a cellular plateau where protein accretion saturates. This concept is illustrated by the work of Gaine et al. (2006), showing that amino acid oxidation increases proportionally to the excess intake. Beyond 2.4g/kg/day, a major part of the amino acids undergoes hepatic deamination, producing ammonia transformed into urea to be excreted. This process, although physiological in healthy subjects, unnecessarily stresses the elimination functions and can influence the systemic acid-base balance.

The ideal intake per serving: clinical evidence

Several key studies allow defining the "efficiency window":

• The minimum threshold: Tang et al. (2007) demonstrated that even a minimal dose of 10g of whey, coupled with carbohydrates, significantly stimulates post-exercise protein synthesis compared to carbohydrates alone.
• Optimization by Leucine: Churchward-Venne et al. (2012) suggest that a 25g dose of whey offers an optimal anabolic response, and the addition of leucine to a sub-optimal dose does not always equal the effectiveness of a complete whole protein dose.
• The maximum useful dose: In the trial by Pennings et al. (2012), the ingestion of 35g of whey showed superiority over lower doses in elderly subjects, underscoring that the need per meal can vary depending on age (anabolic resistance) and the muscle mass involved.

In conclusion, the goal is not to flood the body, but to trigger the "leucine threshold" necessary for anabolism while respecting the individual's metabolic capacities. The literature suggests that a dose of 0.4g/kg per meal is a prudent and effective target (Schoenfeld & Aragon, 2018). To maximize hypertrophy, we recommend 25g for snacks and up to 35-40g for main meals, in order to maintain a stable amino acid concentration without saturating the deamination pathways.

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1. Gaine et al. (2006) - Level of dietary protein impacts whole body protein turnover in trained males at rest.
2. Tang et al. (2007) - Minimal whey protein with carbohydrate stimulates muscle protein synthesis following resistance exercise.
3. Churchward-Venne et al. (2012) - Supplementation of a suboptimal protein dose with leucine or essential amino acids.
4. Pennings et al. (2012) - Amino acid absorption and subsequent muscle protein accretion following graded intakes of whey protein.
5. Schoenfeld & Aragon (2018) - How much protein can the body use in a single meal for muscle-building?