Scoring Zzz’s: Does Whey Protein Supplementation Influence Sleep Outcomes In Adolescent Soccer Players?

PURPOSE: To evaluate the effects of whey protein supplementation on objective and subjective sleep measures in adolescent soccer players over a 10-week competitive soccer season in a double-blind, randomized controlled trial. METHODS: Adolescents athletes (n = 22; 59% female, age: 15.6 ± 0.2; BMI percentile: 55.9 ± 6.2%) were randomized to consume either whey protein (WP; n = 10; 20 g) or an isocaloric placebo (PLA; n = 12) beverage twice per day (once after practice or competition and once 1 hour before bed) for the 10-week competitive season. At baseline (pre-season) and during the final week of the competitive season (post-intervention), total sleep time (TST) and sleep efficiency were measured for 1 week with the Inspire2 Fitbit™, and subjective sleep quality was evaluated with the Pittsburgh Sleep Quality Index (PSQI). The PSQI scores range from 0 to 21, with 0-4 indicating “good” sleep and 5-21 indicating “poor” sleep. RESULTS: There was no difference between WP vs. PLA groups for changes in TST (WP: 7.14 ± 0.37 h to 7.31 ± 0.25 h vs. PLA: 7.33 ± 0.23 h to 7.49 ± 0.37 h, p = 0.1) or sleep efficiency (WP: 92.9 ± 0.65% to 92.1 ± 2.3% vs. PLA: 94.1 ± 0.74% to 94.2 ± 0.45%, p = 0.3), nor was there a main effect of time (p > 0.05 for both). There was also no difference between WP vs. PLA groups for changes in sleep quality (WP: 4.5 ± 0.54 to 2.3 ± 0.58 vs. PLA: 6.7 ± 0.86 to 5.4 ± 0.93, p = 0.38). However, there was a significant effect of time as participants in both groups improved sleep quality from baseline (5.7 ± 2.7) to post-intervention (4.0 ± 3.1; p = 0.006). CONCLUSIONS: There were no additional benefits of whey protein supplementation vs. placebo on TST, sleep efficiency and sleep quality in adolescent athletes over the competitive soccer season. Yet, there may be some benefit to soccer training on subjective sleep quality in this population, especially if training can help individuals obtain “good” subjective sleep as opposed to maintaining “poor” subjective sleep. Although diet, sleep, and athletic performance may be interrelated, further research is needed to evaluate the potential effects of protein supplementation on sleep and, in turn, how sleep may influence performance. Supported by: BUILD Dairy Program