Efficacy of Dietary Supplements on Sports Performance in Elite Athletes

Yu & Ding, Frontiers in Nutrition, 2025

What did the study look at?

A systematic review of 46 randomised controlled trials (928 participants) published between 2014–2024, examining how well dietary supplements actually work for elite athletes.

What were the Key Findings by Supplement?

Caffeine (3–6 mg/kg) — strongest evidence

The most consistently effective supplement. Improved power output, jump height, swimming times, and sport-specific technical skills. Works best for power-based tasks; less effective for precision tasks (e.g., shooting accuracy). Timing matters, taking it in the evening impaired sleep with no performance benefit.

Beta-alanine — sport-specific benefits

Useful for high-intensity efforts lasting 1–10 minutes. One cycling study showed a 3.43% improvement in time trial performance, while the placebo group declined by 6.20%. Requires 4–6 g/day for at least 2–4 weeks to be effective.

Sodium bicarbonate — modest but context-dependent

Small but consistent improvements in high-intensity and repeated-sprint performance, but significant gastrointestinal side effects are a barrier. Progressive-dose loading helped manage this. Gender differences were noted, the benefits seen in male wrestlers but not female wrestlers.

Nitrate (e.g., beetroot juice) — limited in elite athletes

Despite raising plasma nitrate levels, it consistently failed to improve performance in highly-trained cyclists and triathletes. One study even found it impaired a 1 km time trial. The theory is that elite athletes' training adaptations reduce their sensitivity to nitrate.

BCAAs and amino acids — recovery-focused benefits

A BCAA + arginine + citrulline combination prevented central fatigue in elite taekwondo athletes. BCAAs also improved lactate threshold in cyclists. Most useful for recovery and fatigue prevention rather than acute performance.

Probiotics — indirect performance benefits

Didn't directly boost VO₂max, but consistently reduced GI symptoms and perceived exertion. When combined with Vitamin D, showed improved anaerobic power and lactate clearance in MMA athletes.

Vitamin D, Iron, Melatonin

Benefits were highly dependent on baseline deficiency. Vitamin D helped strength in deficient athletes; iron benefits weren't sustained after stopping supplementation; melatonin was only effective under sleep-deprived conditions.

Taurine & Omega-3s

Showed promising results in individual studies (e.g., taurine improved peak power in speed skaters; omega-3s reduced sprint fatigue) but evidence is limited.

Overall Conclusions

There's no one-size-fits-all approach. The authors recommend an individualised, periodised strategy: caffeine for competition days, beta-alanine during pre-competition training blocks, whey/casein for recovery, and BCAAs/probiotics during heavy training weeks.

Let’s LEAN IN - Limitations Worth Knowing

The biggest issue is gender bias.  60% of studies were male-only, with only 10% focused on female athletes. Studies were also small on average (~20 participants), and the heterogeneity of outcomes meant no meta-analysis could be performed. Cycling was heavily over-represented as a sport.

Reference:

Yu T and Ding C (2025) Efficacy of dietary supplements on sports performance outcomes: a systematic review of evidence in elite athletes. Front. Nutr.