Sleep is crucial for athlete recovery and performance, yet many athletes often face challenges with sleep quality. Pre-sleep feeding (PSF) has emerged as a potential strategy to enhance recovery. However, there is limited research on the effects of different macronutrient options on sleep outcomes in elite female athletes.
This study, published in the Journal of the International Society of Sports Nutrition, aimed to explore the impact of pre-sleep milk-derived proteins on sleep and recovery metrics in NCAA Division I female athletes. The randomized controlled trial involved 25 athletes aged 18-25, with 21 completing the study.
Participants consumed four different treatments over three consecutive nights each: 40 g of casein protein (CAS), 40 g of α-lactalbumin protein (ALA), 40 g of carbohydrates (CHO), and a placebo (PLA). The study was conducted over a period of 4-8 weeks, with a minimum three-day washout period between each treatment.
Objective sleep outcomes were measured using the WHOOP 4.0 device, which tracked total sleep time (TST), sleep onset latency (SOL), sleep efficiency (SE), resting heart rate (RHR), and heart rate variability (HRV). Subjective outcomes were assessed through questionnaires that evaluated subjective sleep quality (SSQ), subjective sleep onset latency (SSOL), and subjective recovery (SREC).
Results indicated that there were no significant treatment effects observed for TST, SOL, SE, RHR, or HRV across the different conditions (p > 0.05). TST ranged from 7.47 to 7.62 hours, SE from 91.5% to 92.0%, RHR from 53.5 to 54.1 bpm, and HRV from 98.2 to 103.9 ms. Similarly, no significant differences were found for SSQ, SSOL, or SREC (p > 0.05), with SSQ ranging from 69% to 75%, SSOL from 16 to 20 minutes, and SREC from 61% to 66%.
In a subset of participants, nocturnal interstitial glucose was monitored using continuous glucose monitoring (CGM). While a main effect of time was noted for nocturnal glucose levels (p = 0.008), no significant differences among treatments or treatment interactions were detected.
In conclusion, the findings suggest that pre-sleep ingestion of casein, α-lactalbumin, or carbohydrates does not negatively impact sleep quality or recovery metrics in NCAA Division I female athletes. This indicates that pre-sleep feeding can be safely incorporated into the athletes’ routines without adverse effects on their sleep and recovery.
What this study does not show
This study does not demonstrate any specific benefits of pre-sleep milk-derived proteins on sleep or recovery metrics, only that they do not impair these outcomes.
Evidence scorecard
- Analytic validity: established
- Clinical validity: established
- Clinical utility: established