The Study
Daytime and nighttime casein supplements similarly increase muscle size and strength in response to resistance training earlier in the day: a preliminary investigation
This study is like a fair test where people were randomly split into two groups to see if taking protein at night works better than during the day. Both groups got the same workout and food, so we can trust that any differences (or lack of differences) are likely due to the protein timing. But only 13 people finished the study, so it's a small test and we can't be totally sure the results would be the same for everyone.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
This study checked if drinking a protein shake at night is better than during the day for building muscle when working out.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 558 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes, the results are meaningful—people got noticeably stronger and built visible muscle, whether they drank protein at night or during the day.
- 2Both groups gained about 2–3 kg of muscle and got much stronger—leg press up by 80+ kg and bench press by 11+ kg—over 10 weeks.
- 3No difference based on shake timing.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Journal of the International Society of Sports Nutrition
Year
2018
Authors
J. Joy, R. Vogel, K. Shane Broughton, U. Kudla, Nathaniel Y. Kerr, J. M. Davison, R. Wildman, N. DiMarco
Related Content
Claims (5)
If you're getting the same amount of protein every day, it doesn't matter whether you drink a shake before bed or at another time — you'll gain the same amount of muscle and strength.
If young guys who lift weights drink a protein shake with 35 grams of casein every day — and keep training — they could gain about 2 to 2.8 kilos of muscle in 10 weeks.
If young, active guys lift weights 4 days a week and eat the same total amount of protein, it doesn’t matter whether they have their casein protein late at night or earlier in the day — they’ll gain similar muscle and strength over 10 weeks.
If young guys lift weights in a structured way for 10 weeks, eat about 1.8 grams of protein per kilo of body weight every day, and have supervision, they can get way stronger—adding around 80–85 kg to their leg press and 11–12 kg to their bench press max lifts.
For young guys lifting weights, eating 1.8 grams of protein per kilo of body weight each day is enough to gain muscle and get stronger in 10 weeks — it doesn’t matter if they take a 35g casein protein shake during the day or before bed.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.