Whey protein: a review of the research

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This review sets out what whey-protein studies measured, what they reported and where their findings need qualification. The authorised EU wording appears separately, so you can distinguish it from the research results.

The authorised claims, verbatim

These are the exact, EU-authorised wordings — we don’t combine or intensify them.

What the studies say, outcome by outcome

Muscle mass with resistance training (Morton et al., 2018)

A systematic review, meta-analysis and meta-regression of 49 randomised controlled trials (1,863 participants) studied protein supplementation alongside resistance training (Morton et al., 2018, British Journal of Sports Medicine). It is the largest pooled analysis on the topic. The only effects we state are the authorised EU claims quoted above.

Total daily protein dose-response

As reported in the same paper, the break-point analysis (42 study arms, 723 participants) gave 1.62 g of protein per kilogram of bodyweight per day with a 95% confidence interval of 1.03 to 2.20 and was not statistically significant (p = 0.079). The authors concluded that, with protein supplementation, total protein intakes above about 1.6 g/kg/day did not further contribute to resistance-training-induced gains in fat-free mass (Morton et al., 2018). The ISSN position stand on protein and exercise states that 1.4–2.0 g/kg/day is sufficient for most exercising individuals (Jäger et al., 2017).

Protein type and muscle protein synthesis

The ISSN position stand states that rapidly digested proteins that contain high proportions of essential amino acids and adequate leucine are most effective in stimulating muscle protein synthesis (Jäger et al., 2017).

Per-meal distribution and timing

The ISSN position stand states that recommendations regarding the optimal protein intake per serving for athletes to maximize muscle protein synthesis are mixed and are dependent upon age and recent resistance exercise stimuli, that general recommendations are 0.25 g of a high-quality protein per kg of body weight, or an absolute dose of 20–40 g, and that these protein doses should ideally be evenly distributed, every 3–4 hours, across the day (Jäger et al., 2017).

Practical dosing, as reported by the cited research

• Total daily protein: roughly 1.4–2.0 g/kg/day for most people training regularly (ISSN position stand); Morton et al. (2018) reported no further contribution to fat-free mass gains above about 1.6 g/kg/day with protein supplementation.
• Per serving: a typical whey serving of 20–25 g fits within the 20–40 g per-meal range the position stand describes.
• Distribution: the position stand states that these protein doses should ideally be evenly distributed, every 3–4 hours, across the day (Jäger et al., 2017).

What the evidence does not support

• Protein supplementation without resistance training causing muscle growth. The evidence above is specifically for protein plus a training stimulus; the authorised claim describes protein’s contribution, not a substitute for training.
• A specific “anabolic window.” The position-stand literature treats total daily protein and consistent distribution as the variables that matter; a narrow post-workout timing window is not what the pooled evidence isolates as critical.
• Fat-loss or body-composition claims beyond the authorised wording. The EU claims cover muscle mass growth/maintenance and normal bone maintenance only — we don’t extend whey protein claims into weight-loss or body-composition territory.
• BCAA-specific efficacy claims. Whey is naturally rich in BCAAs, but there is no authorised EU health claim for BCAAs on their own, and we don’t make one. See our EAAs vs BCAAs guide for the compositional detail.

Sources

• Morton RW, Murphy KT, McKellar SR, et al. (2018). “A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults.” British Journal of Sports Medicine, 52(6):376-384. DOI: 10.1136/bjsports-2017-097608 · PMID: 28698222 · PMCID: PMC5867436
• Jäger R, Kerksick CM, Campbell BI, et al. (2017). “International Society of Sports Nutrition Position Stand: protein and exercise.” Journal of the International Society of Sports Nutrition, 14:20. DOI: 10.1186/s12970-017-0177-8 · PMID: 28642676 · PMCID: PMC5477153
• EU Register of authorised nutrition and health claims made on foods (protein claim wordings & conditions of use): ec.europa.eu — EU Register of health claims

This page is part of the CapyFuel Evidence Library — see how we summarise the research and pick sources. For the full practical guide to whey, visit our whey protein hub. Ready to compare prices? See live whey protein pricing in Malta and Cyprus.

Frequently asked questions

Does protein contribute to muscle mass?

Yes, for its authorised effects. The EU-authorised claims apply. The exact EU-authorised wording is shown in the box on this page. Separately, this page describes a large pooled analysis of 49 randomised controlled trials that paired protein with resistance training (Morton et al., 2018).

How much protein do I actually need, according to the research?

The ISSN position stand states that 1.4–2.0 g of protein per kilogram of bodyweight per day is sufficient for most exercising individuals. A 2018 meta-analysis (Morton et al.) reported that, with protein supplementation, total protein intakes above about 1.6 g/kg/day did not further contribute to resistance-training-induced gains in fat-free mass; its break-point was 1.62 g/kg/day (95% confidence interval 1.03 to 2.20).

What does the ISSN position stand say about protein type?

The ISSN position stand (Jäger et al., 2017) states that rapidly digested proteins that contain high proportions of essential amino acids and adequate leucine are most effective in stimulating muscle protein synthesis.

Does timing (the "anabolic window") matter more than total daily protein?

No, based on the cited research. Total daily protein intake, spread reasonably across meals, is what the evidence ties to outcomes. A narrow post-workout timing window is not what the pooled research isolates as the critical variable.

Sources & further reading

1. Morton et al. 2018 — Systematic review, meta-analysis and meta-regression of protein supplementation and resistance-training gains (BJSM, PMC)
2. Jäger et al. 2017 — ISSN Position Stand: protein and exercise (JISSN, PMC)
3. EU Register of authorised nutrition and health claims made on foods (protein claim wordings & conditions of use)