4 claims that cleared review. Each one shows what has to be true for it to hold and how strongly it is supported — including the places the sources contradict each other.
A protein dose of about 20 to 40 grams (providing roughly 10 grams of essential amino acids and 0.7 to 3 grams of leucine) maximizes the acute muscle protein synthesis response from a single meal, with free-form essential amino acids able to reach a similar effect at doses as low as 1.5 to 3 grams.
About 20-40g of protein per meal (or roughly 10g of essential amino acids) fully triggers muscle building. Eating more at once adds no extra benefit; free-form amino acids work at even smaller doses.
Only when
at rest, single dose (minimum effective and plateau thresholds)
free-form essential amino acids are more efficient per gram than intact whey protein at producing an equivalent muscle protein synthesis response
adding essential amino acids on top of a whey protein dose further raises the response beyond whey alone
Who
general adults, including those performing resistance exercise
High confidence
Three independent ISSN-affiliated position-stand papers (Ferrando, Jäger, Kerksick), each a collective authorial voice grounded in RCT-graded evidence, converge on a consistent dose-response picture for acute muscle protein synthesis, with no conflicting findings, no conflicts of interest, and no contradicts_mainstream flags. Noted caveat: as sports-nutrition-society position stands on the same narrow research question, their underlying supporting RCT literature likely overlaps to some degree even though authorship differs.
3 independent people · 3 sources · strongest evidence: rct
Sources
International Society of Sports Nutrition Position Stand: Effects of essential amino acid supplementation on exercise and performance. · Journal of the International Society of Sports Nutrition · 2023 · doi:10.1080/15502783.2023.2263409
International Society of Sports Nutrition Position Stand: protein and exercise. · Journal of the International Society of Sports Nutrition · 2017 · doi:10.1186/s12970-017-0177-8
International society of sports nutrition position stand: nutrient timing. · Journal of the International Society of Sports Nutrition · 2017 · doi:10.1186/s12970-017-0189-4
Eating 20-40 g of high-quality protein per meal (about 0.25-0.40 g/kg body mass), spaced roughly every 3-4 hours, most favorably supports the muscle-protein-synthesis response in adults doing resistance training.
Spreading protein across the day in 20-40g servings, about every 3-4 hours, helps your muscles rebuild and grow more effectively than getting it all in one or two big meals.
Only when
The optimal per-serving amount is mixed across studies and depends on age and recent resistance-exercise stimulus
Who
adults performing resistance training
Moderate confidence
Both sources are International Society of Sports Nutrition consensus position stands rather than independent primary studies, and the two authors have overlapping authorship (kerksick-chad is a co-author on jager-ralf's paper as well as first author of the other) — a case of weak independence per co-appearance/mutual-citation rule, which keeps confidence at moderate despite the rct-tier evidence tag.
2 independent people · 2 sources · strongest evidence: rct
Sources
International Society of Sports Nutrition Position Stand: protein and exercise. · Journal of the International Society of Sports Nutrition · 2017 · doi:10.1186/s12970-017-0177-8
International society of sports nutrition position stand: nutrient timing. · Journal of the International Society of Sports Nutrition · 2017 · doi:10.1186/s12970-017-0189-4
Leucine consumed alone produces only a transient rise in muscle protein synthesis lasting roughly one to two hours, so sustaining an elevated rate of muscle protein synthesis requires a complete source of all essential amino acids -- a high-quality complete protein -- rather than leucine or a subset of amino acids alone.
Taking leucine alone gives only a short 1-2 hour boost to muscle building. For a longer-lasting effect your body needs all nine essential amino acids -- choose a complete protein source instead of isolated leucine or BCAAs.
Only when
applies when leucine (or a small subset of essential amino acids) is consumed alone, without the remaining essential amino acids
the transient response is limited once free essential-amino-acid pools are depleted; continuing synthesis then requires more dietary intake or accelerated protein breakdown
sustaining synthesis after the initial leucine-triggered response requires a higher total dose of all essential amino acids, best supplied by a complete, high-quality protein source
Who
general adults, particularly those resistance training for muscle protein synthesis
Moderate confidence
Two independent ISSN position-stand authors (ferrando-arny, jager-ralf) converge on this mechanistic point; no co-authorship or mutual-citation overlap is documented between them in the person registry, so independence is not discounted here. Both supporting evidence entries are mechanistic (not RCT or observational), a mid tier on the evidence ladder, which caps confidence at moderate rather than high.
2 independent people · 2 sources · strongest evidence: mechanistic
Sources
International Society of Sports Nutrition Position Stand: Effects of essential amino acid supplementation on exercise and performance. · Journal of the International Society of Sports Nutrition · 2023 · doi:10.1080/15502783.2023.2263409
International Society of Sports Nutrition Position Stand: protein and exercise. · Journal of the International Society of Sports Nutrition · 2017 · doi:10.1186/s12970-017-0177-8
Skeletal muscle remains sensitized to protein feeding for at least 24 hours after a bout of resistance exercise -- a substantially longer window than the traditional narrow post-workout 'anabolic window' -- so eating a protein-containing meal or snack sometime within that window is enough to gain the associated muscle-protein-synthesis benefit, even though the exact minute of ingestion is not critical.
Your muscles stay primed to build from protein for about a day after a workout, not just the minutes right after. Eat protein sometime that day; the exact timing barely matters.
Only when
window applies for at least 24 hours following a resistance-exercise bout
the precise minute of ingestion within that window is not critical, though the pragmatic recommendation is to eat protein as soon as convenient rather than delaying for hours
skipping protein entirely after a workout confers no benefit
Who
adults performing resistance training
Moderate confidence
Two independent ISSN position-stand papers (Jäger, Kerksick) agree on a roughly 24-hour post-exercise protein-sensitization window; the strongest support is RCT-graded, so confidence is not capped at low or moderate by the author-assertion or spoken-only rules. However, only two independent people back it, and one member (Kerksick's mechanistic claim) explicitly flags contradicts_mainstream against the older, narrower 'anabolic window' framing, so this is treated as a revision to older folk advice rather than settled uncontested consensus.
2 independent people · 2 sources · strongest evidence: rct
Sources
International Society of Sports Nutrition Position Stand: protein and exercise. · Journal of the International Society of Sports Nutrition · 2017 · doi:10.1186/s12970-017-0177-8
International society of sports nutrition position stand: nutrient timing. · Journal of the International Society of Sports Nutrition · 2017 · doi:10.1186/s12970-017-0189-4
This is a summary of published research, not medical advice. It cannot account for your medications, conditions or history. Talk to a clinician before acting on any of it.