35 Impact of Whey Protein Supplementation on Body Composition and Athletic Performance in High School Soccer Players

Faculty Mentor: Tanya Halliday (Health, Kinesiology, and Recreation, University of Utah)

Introduction

During adolescent years, adequate protein intake is critical as a teenager develops rapidly during puberty (1). Unlike adults, adolescents must maintain a positive nitrogen balance to facilitate the process of growth, which is accomplished by adequate protein consumption (2).

Special attention should be given to adolescent athletes who have higher dietary protein requirements than general adolescents to support recovery following bouts of physical activity and exercise (3). The recommended dietary protein intake for adolescent athletes is 1.3-1.8 g/kg of body weight (3). For the median weight 16-year-old male athlete (64 kg) this would be a protein requirement between 83-115 grams per day, and for the median weight 16-year-old female athlete (55 kg) this would be a protein requirement between 71-99 grams per day (4).

These intake guidelines are much higher than the recommended protein intake levels for the general adolescent population which are 52 grams per day for males aged 14-18 and 46 grams per day for females aged 14-18 (5).

Whey protein is a safe and common source of high-quality protein that can be used to help meet recommended protein intakes. While there has been ample research conducted on the influence of whey protein supplementation on body composition in active/athletic adult populations, this work has not been thoroughly conducted in adolescents. Evidence from trials in active/athletic adult populations have demonstrated that whey protein supplementation, when taken with resistance training intervention can increase lean body tissue (6). Increased levels of lean body mass have been shown to be positively correlated with performance in Olympic weightlifters (7) and peak VO2 levels in adolescents (8). This suggests that whey protein has performance benefits due to its anabolic effects on lean body mass. However, little is known about the effects of whey protein supplementation on these outcomes in active adolescents.

The purpose of this randomized clinical trial is to determine the effect of whey protein supplementation in high school athletes on performance, body composition, and recovery. The present UROP analysis is focused on changes in body composition and athletic performance.

Methods

Adolescent Soccer players (n=22, 59% female, age: 15.6 ± 0.2 years) underwent assessments of body composition (fat mass and fat-free mass via air displacement plethysmography), cardiorespiratory fitness (sprint time via 30-yard dash and VO2max via 1.5- mile run), and muscular fitness assessments (peak torque via isometric muscle contraction, and endurance via repetitions to fatigue) at pre- and post-intervention. Participants were blinded and randomly assigned to consume whey protein (WP; 2.5g carbs, 0.8g fat, 20g protein, 100 kcals) or an isocaloric placebo (PLA; 23.2g carbs, 0.96g fat, 0g protein, 100 kcals) twice per day, once after practice or competition and once before bedtime, for the 10-week Fall soccer season.

Results

There was no difference between the WP and PLA groups for changes in body composition, sprint time, VO2max, or muscle peak torque (all p>0.05) However, fat mass decreased (pre=12.3 ± 1.4kg, post=11.4 ± 1.2kg; p<0.001), fat-free mass increased (pre=46.435 ± 6.38kg, post=47.18 ± 6.70kg; p<0.001), sprint time decreased (pre=4.95 ± 0.37s, post=4.78 ± 0.37s; p=0.003), and VO2max increased (pre=42.79 ± 6.30mL/kg/min, post=46.07 ± 6.87mL/kg/min; p<0.001) in both groups from pre- to post intervention. The only difference between groups detected was that PLA increased their muscular endurance compared to WP (0.6 ± 0.4 reps vs. -1.7 ± 1 reps, respectively, p=0.028). They also increased their peak torque (169.6± 8.3 tq vs. 167.2 ± 7.9 tq, respectively, p=0.001).

Discussion

The results show that there were some differences between the WP group and PLA group when it came to muscular endurance and peak torque, but everything else stayed relatively the same. Body composition and cardiorespiratory fitness improved in both groups, as a result of their training and competition schedule. Cardiorespiratory fitness increased due to the nature of the sport. This study is unique because it examined the impact of whey protein on an understudied population, and was also conducted during an active competitive high school soccer season. This adds to the current literature on the impact of whey protein on body composition and athletic performance. Additional research should be conducted, particularly in strength-training focused adolescent populations.

Conclusion

There were no beneficial changes in body composition and athletic performance from whey protein supplementation vs. placebo during the 10-week intervention indicating whey protein may not have additional benefits when consumed across a competitive soccer season.

References

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