Editorial: Advancements in Dietary Supplements: Enhancing Sport Performance and Recovery

Mark Elisabeth Willems^1*Laurel M Wentz²David Christopher Nieman²

• ¹University of Chichester, Chichester, United Kingdom
• ²Appalachian State University, Boone, United States

The consumption of dietary supplements is common among athletes and recreationally active individuals. The number of studies listed in the reputable database PubMed from the National Library of Medicine (USA) with the search strategy for a phrase in the title or abstract, i.e. "dietary supplements" [Title/Abstract] OR "dietary supplement" [Title/Abstract]" will soon reach more than 20000 records. Very few dietary supplements have been linked scientifically to enhanced athletic performance or recovery. Supplements with strong scientific evidence include creatine, caffeine, β-alanine, protein, and nitrate (1). Most other supplements have mixed scientific support or remain unproven and even risky. A food first approach based on a well-balanced, nutrient-rich diet is recommended for most athletes and exercisers (2). A sports nutrition professional can be contacted for guidance before taking any supplement. The Research Topic "Advancements in Dietary Supplements: Enhancing Sport Performance and Recovery" has one review and four experimental studies contributing to our understanding for the ergogenic potential and application of dietary supplements in diverse cohorts. In the article "Emerging evidence of Urolithin A in sports nutrition: bridging preclinical findings to athletic applications", Wang and Yu provided information to warrant future research on Urolithin A. Urolithin A is a gut derived metabolite from the intake of ellagatins and ellagic acid, both a type of polyphenol which are present for example in walnuts and pomegranate. The inter-individual variability in urolithin availability from natural sources is age-dependent with 10% non-producers independent of age (3). Nevertheless, Urolithin A may have application as a dietary and sports nutrition supplement based on potential anti-oxidant effects that may reduce muscle fatigue and support cardiovascular function. Based on the studies covered in the review by Wang and Yu, recommendations are provided for the dosing strategy for Urolithin A to be used in future exercise studies. The remaining four studies in the Research Topic are experimental studies. The study by Zhu et al "Effects of progressive versus consistent dose of caffeine ingestion on volleyball players' exercise performance adaptations following plyometric jump training" examines different caffeine dosing strategies. Most dietary supplement studies use a constant dose to examine ergogenic potential. Lara et al (4) suggested increased caffeine tolerance with a constant dose (3 mg/kg body weight) over 20 days. Zhu et al observed that a progressive dose of caffeine (3 mg/kg body weight to 6 mg/kg body weight) over 4 weeks combined with plyometric jump training in male Chinese volleyball players was as effective on high-intensity exercise and agility observations as a constant high dose of 6 mg/kg body weight. Combined use of dietary supplementation is likely common although most studies on the prevalence of dietary supplements do not report on combined use (5). Abdioglu et al examined the effects of combined use of carbohydrate gels and caffeinated chewing gum in male junior Turkish tennis players. Combined use effects on ground strokes was better than the control and placebo chewing gum with lower RPE values during the game-simulated tennis tasks. While there was no difference in performance outcomes identified in this study, combined supplementation of carbohydrate gel and caffeinated gum may reduce fatigue with potential performance effects throughout the tennis season. The understanding of the effectiveness of dietary supplements needs to recognize the inter-and intra-individual responses (6). Niknam et al examined the individual responses to the intake of purple grape juice (10 ml/kg of body mass) in a cohort of 22 elite male Iranian soccer players under 20 years of age. Their findings highlight that purple grape juice had more participants meaningful responding during the exercise required during the 30-15 Intermittent Fitness Test (~74%) than the recovery measurement of a standing long jump from the exercise (54%). Studies that address the inter-individual responses, including Niknam et al, will contribute to the application of personalized use of dietary supplements. Finally, the article by Wang et al examines the effect dietary nitrate (beetroot) in college male Chinese body builders. Beetroot is a popular dietary supplement (7) and is known to be ergogenic for endurance activities. Wang et al observed in repeated isometric circuit endurance tests (four rounds) with different muscle groups enhanced endurance in the third round of testing. Endurance was improved by 14.9, 25.4, and 25.2% for the elbow flexors, forearm muscles, and knee extensor muscles. The findings suggest that a level of fatigue is required for beetroot to be effective and potentially affecting the recovery process between isometric tasks in body building. The numerous factors to be considered for the effectiveness of dietary supplements on exercise performance and recovery such as age, training status, skill level, sport, sex, ethnicity, habitual diet, gut microbiome among others, and not to mention new compounds will make the endeavour of experimental studies to meaningful advance the field a challenging undertaking. The contribution of the articles in this Special Issue "Advancements in Dietary Supplements: Enhancing Sport Performance and Recovery" is humble considering the vastness of unexplored issues.