Protein builds muscle — everyone knows that. But how much do you actually need? Is it true that the body can't use more than 30 g per meal? Is whey really better than plant sources? The answers are in the literature — and they're not always what you'd expect.
How much protein per day?
The official recommendation (RDA) is 0.8 g/kg body weight per day — but that's the minimum to prevent deficiency, not the optimum for muscle growth or athletic performance.
The landmark meta-analysis by Morton et al. (2018, British Journal of Sports Medicine, 49 studies, 1,863 participants) found that the optimal intake for maximizing muscle protein synthesis is ~1.6 g/kg/day, with an upper confidence limit of 2.2 g/kg/day. Beyond 1.6 g/kg, returns diminish.
Tagawa et al. (2023, Nutrition Reviews) confirmed in a dose-response meta-analysis that muscle mass increases proportionally with protein intake up to a breakpoint at ~1.3 g/kg/day — beyond which the efficiency of converting protein into muscle mass declines, though resistance training mitigates this decline.
Nunes et al. (2022, Journal of Cachexia, Sarcopenia and Muscle) confirmed that additional protein increases lean body mass in both young and older adults — but only when combined with exercise.
How much per meal? The "30 g limit" myth
A common myth says the body can't use more than 30 g of protein at once. This isn't true — the body absorbs virtually all ingested protein. The limit isn't in digestion, but in muscle protein synthesis (MPS).
Schoenfeld & Aragon (2018, Journal of the International Society of Sports Nutrition) concluded that MPS is maximized at ~0.4–0.55 g/kg per meal (~30–40 g for most people). More protein per meal isn't "wasted" — but the excess goes to energy metabolism, not additional muscle synthesis.
Practical implication: 3–4 meals with evenly distributed protein per day is the optimal strategy. Mamerow et al. (2014, Journal of Nutrition) confirmed that even distribution (~30 g per meal) stimulates 25% more 24-hour MPS than uneven distribution (10 g/16 g/65 g).
Plant vs. animal sources
Hevia-Larraín et al. (2021, Sports Medicine) compared vegans and omnivores performing the same 12-week training program with equal protein intake (1.6 g/kg). Result: no difference in muscle mass or strength between groups — provided total intake was sufficient and plant sources contained adequate leucine.
Jäger et al. (2024, Journal of the International Society of Sports Nutrition) in the updated ISSN position stand confirmed that plant proteins are effective for muscle growth, but recommend combining different sources (legumes + grains) for a complete amino acid profile and sufficient leucine (≥2.5 g per meal).
Kerksick et al. (2024, Journal of the International Society of Sports Nutrition) in the 10th anniversary update emphasize that protein quality matters — whey, casein, eggs, and soy have the highest DIAAS scores (digestibility), while grain proteins require higher intake for the same effect.
Timing: is the "anabolic window" real?
The old belief that you must eat protein within 30 minutes post-workout is overstated. Schoenfeld & Aragon (2018) concluded that total daily intake and even distribution matter more than precise timing. That said, a protein-containing meal within 2–3 hours of training is sensible, especially if you trained fasted.
Stokes et al. (2018, Nutrients) confirmed that post-exercise muscle sensitivity to amino acids remains elevated for 24–48 hours — not just the first 30 minutes. So: don't panic about the "window," but don't skip meals either.
References
- Hevia-Larraín, V. et al. (2021). High-protein plant-based diet versus a protein-matched omnivorous diet to support resistance training adaptations. Sports Medicine, 51(6), 1317–1330.
- Jäger, R. et al. (2024). International Society of Sports Nutrition position stand: protein and exercise (updated). Journal of the International Society of Sports Nutrition, 21(1).
- Kerksick, C.M. et al. (2024). ISSN exercise & sports nutrition review update: research & recommendations (10th anniversary). Journal of the International Society of Sports Nutrition, 21(1).
- Mamerow, M.M. et al. (2014). Dietary protein distribution positively influences 24-h muscle protein synthesis in healthy adults. Journal of Nutrition, 144(6), 876–880.
- Morton, R.W. et al. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains. British Journal of Sports Medicine, 52(6), 376–384.
- Nunes, E.A. et al. (2022). Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults. Journal of Cachexia, Sarcopenia and Muscle, 13(2), 795–810.
- Schoenfeld, B.J. & Aragon, A.A. (2018). How much protein can the body use in a single meal for muscle-building? Journal of the International Society of Sports Nutrition, 15, 10.
- Stokes, T. et al. (2018). Recent perspectives regarding the role of dietary protein for the promotion of muscle hypertrophy. Nutrients, 10(2), 180.
- Tagawa, R. et al. (2023). Dose-response relationship between protein intake and muscle mass increase: systematic review and meta-analysis. Nutrition Reviews, 79(1), 66–75.
Important notice
This article is for informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment, and is not a substitute for professional medical consultation.
All decisions regarding health, nutrition, exercise, or lifestyle changes should always be discussed with your physician, who understands your complete medical history.
The author is not a medical doctor and assumes no liability for any consequences arising from the use of this information without medical supervision.