Protein Powder: The Evidence-Based Guide to Choosing and Using
Complete science-based guide to protein powder: whey vs casein vs plant, optimal timing, evidence-backed dosing, and who actually needs supplementation.
Lead Science Writer · Peer-Reviewed Sources
Protein supplementation is one of the most researched areas in sports nutrition. Yet the marketing noise makes it nearly impossible to separate what matters from what sells.
Does Protein Powder Work?
Yes — but context matters. A 2018 meta-analysis by Morton et al. in the British Journal of Sports Medicine analyzed 49 RCTs (1,863 participants) and found protein supplementation significantly increased:
- Muscle mass: +0.30 kg (95% CI: 0.09-0.52)
- Maximal strength: +2.49 kg for 1RM (95% CI: 0.64-4.33)
The effect was most pronounced in resistance-trained individuals consuming >1.6g/kg/day total protein.
Whey vs Casein vs Plant: What the Research Shows
Whey protein dominates the literature. Its rapid absorption kinetics and high leucine content (~10-11% by weight) make it the most studied and consistently effective option for muscle protein synthesis (MPS).
Casein absorbs slowly, producing a sustained aminoacidemia. Useful before prolonged fasting (sleep). A 2012 study by Res et al. showed 40g casein before bed increased overnight MPS by 22%.
Plant proteins (pea, rice, soy) can match whey when:
- Total daily protein intake is adequate (>1.6g/kg)
- Leucine content is supplemented or blended sources are used
- Per-serving dose is slightly higher (~30-40g vs 20-25g for whey)
How Much Protein Do You Actually Need?
The current evidence supports:
| Goal | Protein Intake |
|---|---|
| General health | 0.8-1.0 g/kg/day |
| Muscle maintenance | 1.2-1.6 g/kg/day |
| Muscle growth | 1.6-2.2 g/kg/day |
| Fat loss + muscle retention | 2.0-2.4 g/kg/day |
| Older adults (>65) | 1.2-1.6 g/kg/day minimum |
The 2017 ISSN position stand confirms there is no credible evidence that protein intakes up to 2.2g/kg/day cause kidney damage in healthy individuals.
Timing: Does It Matter?
The "anabolic window" is largely a myth. Total daily protein intake matters far more than timing. However:
- Distributing protein across 3-5 meals optimizes 24-hour MPS
- Post-exercise protein within 2-3 hours is reasonable, not urgent
- Pre-sleep protein (casein) has genuine supporting evidence
When Supplementation Makes Sense
- You cannot meet protein targets through whole food alone
- Convenience matters (travel, work, post-training)
- You are vegan/vegetarian and struggle with leucine-rich sources
- You are an older adult with reduced appetite
Protein powder is a food supplement, not a magic powder. If you eat enough chicken, fish, eggs, and dairy — you probably do not need it.
Sources: Morton et al. (2018) BJSM, Res et al. (2012) Med Sci Sports Exerc, Jäger et al. (2017) ISSN Position Stand, Messina et al. (2018) Plant protein meta-analysis