LifestyleExercise

Presleep whey protein ingestion improves sleep quality after resistance exercise compared with an isocaloric control in resistance-trained individuals

In a randomized, double-blind, crossover trial of nine resistance-trained young adults, consuming 40 g of whey protein 30 minutes before bed significantly improved sleep-onset latency (9.0 vs 19.0 min), sleep efficiency (96% vs 93%), total sleep time (400 vs 363 min), and subjective sleep rating (8.0 vs 6.0) compared with an isocaloric maltodextrin control. Whey also reduced delayed onset of muscle soreness at 12 and 24 hours post-training.

Last updated: Jul 9, 2026•1 RCTs•📖 Read as article →

Evidence Score

Evidence Score44/100
Human RCT★★☆☆☆
Meta-analysis☆☆☆☆☆
Mechanism★★★★★
Safety★★★★☆
Confidencelow

Study Evidence

Study 1. Presleep Whey but Not Casein Protein Ingestion Improves Sleep Quality After Resistance Exercise When Compared With an Isocaloric Control in Resistance Trained Individuals.

observational

Aussieker T, Kredig N, Wasserfurth P, Harmsen JF, Spitschan M, Koehler K · International journal of sport nutrition and exercise metabolism (2026)

Participants: N/A
Duration: Single night per condition (crossover design)
Intervention: 40 g of whey protein ingested 30 minutes before bedtime
Outcome: Sleep quality (sleep-onset latency, sleep efficiency, total sleep time, subjective sleep rating), delayed onset of muscle soreness
Effect Size: N/A (median and interquartile ranges reported, no effect size given)
Population: Nine young, healthy, resistance-trained men (n=5) and women (n=4), mean age 24 ± 2 years, BMI 24.4 ± 2.9 kg/m²

Result:

PubMed: 42413910DOI: 10.1123/ijsnem.2025-0205

Mechanism Graph

Whey protein is rapidly digested and absorbed, increasing plasma amino acids
↓
Increased amino acid availability may promote neurotransmitter synthesis (e.g., serotonin) involved in sleep regulation
↓
Whey protein ingestion may reduce muscle soreness, indirectly improving sleep quality
↓
Result: Improved sleep-onset latency, efficiency, total sleep time, and subjective sleep rating

Limitations

  • ⚠Small sample size (n=9) limits generalizability
  • ⚠No direct comparison of whey vs casein showed significant differences, so the specific advantage of whey over casein is not confirmed
  • ⚠Actigraphy-based sleep measures may be less accurate than polysomnography
  • ⚠Short-term, single-night intervention; long-term effects unknown

Frequently Asked Questions

Does whey protein before bed improve sleep quality in athletes?▼

This study suggests that 40 g of whey protein taken 30 minutes before bed can improve sleep-onset latency, efficiency, total sleep time, and subjective sleep quality after resistance exercise in trained individuals.

How does whey protein compare to casein for sleep?▼

Whey protein significantly improved several sleep measures compared to an isocaloric control, but differences between whey and casein were not statistically significant in this small study.

Does whey protein cause gastrointestinal issues before sleep?▼

No significant differences in gastrointestinal symptoms were reported between whey, casein, and control conditions in this study.

Can whey protein reduce muscle soreness after exercise?▼

Yes, whey protein ingestion led to a significant reduction in delayed onset of muscle soreness at 12 and 24 hours post-training compared to the control.

Products

Affiliate links coming soon. We only recommend products that match the doses and forms used in the cited research.

References

  1. 1.Aussieker T, Kredig N, Wasserfurth P, Harmsen JF, Spitschan M, Koehler K. "Presleep Whey but Not Casein Protein Ingestion Improves Sleep Quality After Resistance Exercise When Compared With an Isocaloric Control in Resistance Trained Individuals.." International journal of sport nutrition and exercise metabolism, 2026. PMID: 42413910 DOI: 10.1123/ijsnem.2025-0205
Disclaimer: This content is for educational purposes only and is not medical advice. Evidence scores reflect the quality and quantity of available research, not clinical recommendations. Always consult a healthcare professional before starting any supplement or intervention.