You see swimmers chugging beet juice and popping beta-alanine, but what actually works when the clock is ticking? In a sport where 1.6% can be the difference between first and fourth place at the Olympics, every edge counts. The supplement aisle is full of promises, but the science is often murky.
Fortunately, a massive new systematic review and meta-analysis published in 2025 in the Journal of the International Society of Sports Nutrition just cut through the noise. Researchers analyzed 23 high-quality studies on competitive swimmers to find out which supplements deliver real, measurable performance benefits. The results are in, and there's one clear winner.
The Clear Winner: Creatine
Across all the supplements put under the microscope, only one showed a statistically significant positive effect on swimming performance in the meta-analysis: creatine.
The analysis reported a small-to-moderate effect size (ES = −0.46), confirming that creatine supplementation helps swimmers get faster compared to a placebo. This isn't surprising to many in the strength world, but it's a huge confirmation for the swimming community.
How does it work? Creatine boosts your intramuscular stores of phosphocreatine (PCr), the high-energy compound your body uses for explosive, short-duration efforts. By increasing PCr availability, your muscles can resynthesize ATP (your body's energy currency) faster, delaying fatigue and improving performance.
Individual studies included in the review found that creatine helped swimmers:
- Improve performance in 50-yard and 100-yard events.
- Swim a 50-m test 4.5% faster.
- Increase velocity during the final 50 meters of a 400-meter race.
- Perform better during interval training sessions.
The Coach's Corner: The evidence is strong here. Creatine is a proven performer. One thing to keep in mind is that it can increase water retention, leading to a quick jump in body mass. While this might be a concern for some, the performance benefits appear to outweigh this potential downside. The studies reviewed were also short-term (6 to 14 days), so long-term integration with training cycles is the next frontier.
The "Maybes": Buffering Agents
What about supplements that fight that burning sensation during an all-out sprint? The review looked at two popular buffering agents: beta-alanine and sodium bicarbonate (SB).
These supplements work by helping to manage the drop in pH (increase in acidity) that happens during intense exercise. The meta-analysis, which grouped these two supplements together, found no significant overall effect on performance.
However, that doesn't mean they're useless. Individual studies tell a more nuanced story:
- Beta-Alanine: One study found it improved 100-m and 200-m time trial performance after six weeks of use. It works by increasing muscle carnosine levels, which acts as an intracellular buffer.
- Sodium Bicarbonate: An elite group of male swimmers improved their 200-m time trial performance with SB. It works by increasing bicarbonate in the blood, acting as an extracellular buffer.
The Coach's Corner: The jury is still out on these for swimmers based on this review. While the overall meta-analysis was inconclusive, individual results suggest they could be beneficial for high-intensity events. Be aware of the side effects: beta-alanine can cause a harmless tingling sensation (paresthesia), and sodium bicarbonate is notorious for causing GI distress. Proper dosing and timing are critical.
Interestingly, one study found that combining beta-alanine and SB led to the greatest performance improvements in a 200-m test, suggesting a potential synergistic effect.
The Surprising "Not Yets": Caffeine & Beetroot Juice
Two of the most popular ergogenic aids in sports, caffeine and beetroot juice, did not show significant performance-enhancing effects in the meta-analysis.
Caffeine
Caffeine is the most-consumed supplement by elite swimmers, and for good reason—its effects on the central nervous system are well-documented. It blocks adenosine receptors, reduces the rate of perceived exertion (RPE), and can increase muscle recruitment.
Despite this, the meta-analysis (which only included three studies on caffeine) found no significant effect. However, individual studies did show it enhanced performance in 50-m and 50-yard tests. The limited number of studies likely impacted the overall statistical power.
Beetroot Juice (BRJ)
BRJ is a source of dietary nitrates, which your body converts to nitric oxide (NO). NO can improve blood flow and make muscle contractions more efficient. The meta-analysis, however, found no significant improvement in swimming performance.
But dose might be the key. The review noted that studies using lower doses of nitrate found no effect, while those using higher doses (above 8.4 mmol of NO₃) reported trends toward improved performance, especially in the later sets of interval protocols.
The Coach's Corner: Don't throw out your pre-workout coffee or beet juice just yet. For caffeine, the general body of evidence is still strong, even if this swimming-specific meta-analysis was inconclusive. For BRJ, it seems the effect might be limited to higher doses and could be most useful for maintaining performance during tough interval sets.
The Rest of the Pack
The review also briefly touched on a few other supplements:
- L-Arginine/L-Citrulline: These NO precursors failed to show any effect on swimming performance.
- Probiotics: One study found no performance benefit, though swimmers reported a slightly improved perception of recovery.
- Rice Germ: A single study reported faster 200-m swim times, but the authors noted the study had significant limitations and didn't control for calorie intake.
Final Takeaways for Coaches and Athletes
This 2025 meta-analysis provides the clearest picture yet of the supplement landscape for competitive swimmers.
- Go with Creatine: It's the only supplement with strong, statistically significant evidence of performance enhancement from this meta-analysis.
- Consider Buffers Carefully: Beta-alanine and sodium bicarbonate might offer an edge in high-intensity events, but the evidence isn't as robust. Experimentation during training is key.
- Be Patient with Caffeine and BRJ: While the meta-analysis was underwhelming, there's still reason to believe they could work under the right conditions (e.g., higher doses for BRJ).
- Stacking Might Be the Future: The most intriguing findings came from studies combining supplements, like beta-alanine with SB or creatine with SB. This is an area ripe for more research.
Remember, supplements are the final piece of the puzzle. They can't replace a foundation of elite training, smart nutrition, and dedicated recovery. Use this evidence to make informed decisions and find that extra edge when it counts.
Source Article: Domínguez, R., López-León, I., Moreno-Lara, J., Rico, E., Sánchez-Oliver, A. J., Sánchez-Gómez, Á., & Pecci, J. (2025). Sport supplementation in competitive swimmers: a systematic review with meta-analysis. Journal of the International Society of Sports Nutrition. https://pubmed.ncbi.nlm.nih.gov/40205676/