Supplements for HYROX® and triathlon: what has evidence
By the Tuffr team · Last updated · 10 min read
Five supplements have research behind them for endurance and hybrid racing: caffeine, creatine, beta-alanine, dietary nitrate and sodium bicarbonate. The IOC gives caffeine, creatine, nitrate and bicarbonate good to strong evidence in specific situations only, and caffeine fits the widest range of events. Test anything in training first.
Which supplements have good evidence for a fitness race or triathlon?
The IOC consensus statement of 2018 names caffeine, creatine, sodium bicarbonate and nitrate among the few supplements with good to strong evidence, each only in specific situations. Event length decides the fit. A fitness race takes about 60 to 100 minutes, and a half or full triathlon takes roughly 5 to 17 hours (our estimate).
| Supplement | What it may help | Evidence | Fit: fitness race (60 to 100 min) | Fit: triathlon (5 to 17 h) |
|---|---|---|---|---|
| Caffeine | Endurance efforts of about 5 to 150 minutes, sprints and alertness | Well established benefits (IOC); the ISSN reports consistent gains at 3 to 6 mg per kg | Good fit: the race length is inside the studied range | Partial fit: longer than most studies; the IOC allows lower doses split before and during exercise |
| Creatine | Repeated high-intensity efforts under about 150 seconds, strongest under 30 seconds, plus strength training and lean mass | Good to strong in those situations (IOC); the ISSN calls it the most effective supplement for high-intensity capacity and lean mass | Unclear: short hard efforts such as the sleds may benefit, but we found no study in this race format | Poor fit: the IOC warns that 1 to 2 kg of extra body mass may hurt endurance performance |
| Beta-alanine | Sustained high-intensity efforts of about 30 seconds to 10 minutes | Possible and small, about 0.2 to 3 percent, with large differences between people (IOC); the ISSN says the largest effects are at 1 to 4 minutes | Unclear: a race is mostly longer than 4 minutes, and the ISSN asks for more research beyond 25 minutes | Poor fit for the same reason |
| Dietary nitrate (beetroot juice) | Prolonged submaximal exercise, time trials under about 40 minutes (1 to 3 percent) and intermittent efforts of 12 to 40 minutes | Good to strong in specific situations (IOC); a 2021 meta-analysis of 73 studies found more power output and time to exhaustion, but no change in time-trial performance | Uncertain: the gains quoted are for efforts up to 40 minutes, so expect a small effect at best | Not shown for multi-hour racing in the sources we opened |
| Sodium bicarbonate | High-intensity efforts of about 30 seconds to 12 minutes (ISSN) | Good to strong in specific situations (IOC); the ISSN has a position stand from 2021 | Weak fit: the hard bursts are short, but they are spread across a long race, and the IOC says the effect fades past about 10 minutes | Poor fit: the efforts are far longer than 12 minutes, and gut problems can cost time |
What each supplement may help and where it fits (evidence from the IOC 2018 statement and ISSN position stands; the two fit columns are our reading)
None of the papers we opened tested these supplements in a fitness race, so read the fit columns as judgement and not as a result. For what to eat and drink during the race itself, see fuelling a fitness race and half-distance fuelling.
What doses did the studies use?
These are the doses that studies and position stands report. They are studied doses, not advice for you. Most are scaled to body mass, so a 70 kg athlete multiplies the per-kilogram figure by 70, and timing matters as much as the amount. People respond differently, so a dose that worked in a study may not work for you.
| Supplement | Studied doses | Studied timing | Source |
|---|---|---|---|
| Caffeine | 3 to 6 mg per kg of body mass (210 to 420 mg for 70 kg); about 2 mg per kg may be the lowest effective dose, and about 9 mg per kg adds side effects without more benefit | About 60 minutes before exercise; lower doses can be split before and during exercise | ISSN caffeine position stand, 2021; IOC 2018 |
| Creatine | Loading of about 0.3 g per kg a day for 5 to 7 days, then 3 to 5 g a day; 3 to 5 g a day alone also fills the stores, over 3 to 4 weeks | Taken every day; there is no race-day timing | ISSN creatine position stand, 2017 |
| Beta-alanine | 4 to 6 g a day for at least 2 to 4 weeks, in divided doses | Taken every day; the benefit builds over weeks | ISSN beta-alanine position stand, 2015 |
| Dietary nitrate (beetroot juice) | A single dose of 5 to 9 mmol, about 310 to 560 mg of nitrate; the benefit did not grow above about 8.4 mmol | 2 to 3 hours before exercise; intake over more than 3 days may also help | IOC 2018 |
| Sodium bicarbonate | 0.2 to 0.5 g per kg, with 0.3 g per kg called optimal and 0.2 g per kg the minimum effective dose | 60 to 180 minutes before exercise; multi-day plans of 3 to 7 days with a split daily dose also exist | ISSN sodium bicarbonate position stand, 2021 |
Studied doses and timing (for a 70 kg athlete the per-kilogram figures are our arithmetic)
Higher doses are not better. For caffeine and bicarbonate the position stands report more side effects at higher doses with no extra benefit.
What are the side effects of these supplements?
Gut trouble is the main risk with sodium bicarbonate, extra water weight with creatine, tingling with beta-alanine, and jitters or poor sleep with high doses of caffeine. Most problems show up the first time you take something, which is why race day is the wrong day to try it.
| Supplement | Known side effects | What the sources suggest |
|---|---|---|
| Caffeine | Nausea, anxiety, insomnia and restlessness, mostly at high doses | Stay in the 3 to 6 mg per kg range; the response depends on how much caffeine you normally have and on your genes |
| Creatine | Weight gain of 1 to 2 kg, mainly water; otherwise considered safe for healthy people at the studied doses | Weigh the extra body mass if you run or if you have a weight target |
| Beta-alanine | Tingling of the skin (paraesthesia); the IOC also lists skin rashes | Smaller divided doses or a sustained-release form reduce the tingling |
| Dietary nitrate (beetroot juice) | Few reported; some athletes get stomach upset | Try it in training first |
| Sodium bicarbonate | Bloating, nausea, vomiting and abdominal pain, which can hurt performance | Smaller or split doses, a carbohydrate-rich meal or enteric-coated capsules reduce the risk |
Known side effects and what the sources suggest
Important
Talk to a doctor before you start any supplement if you take medication, are pregnant or have a health condition. This guide is general sports nutrition information, not medical advice. Stop and get medical help if you feel unwell.Are supplements safe for anti-doping rules?
Not automatically. The IOC notes that supplements are regulated like food in most countries, so what is in the tub is rarely verified, and a product can contain a banned substance that the label does not list. Under the anti-doping rules, an athlete answers for what is in the body, whatever the intent.
- Read the label and avoid blends with vague names. The IOC advises due diligence on every product.
- Prefer single-ingredient products whose batch was tested by an independent third party. The IOC calls third-party audited products lower risk but says no product can be guaranteed safe. This is our reading of that advice.
- Keep the batch number and a photo of the label for as long as you use the product (our recommendation).
- If your race has doping control, or you hold a licence, ask the organiser or your national anti-doping body before you start (our recommendation).
We do not name products or link shops. The same principle applies to a caffeine gel or a beetroot shot as to a powder.
Which supplements are not worth it?
Skip anything that solves a problem you do not have. The clearest example is BCAA powder. A 2022 systematic review of 24 studies found negligible effects on performance and body composition, and most studies did not report total protein intake, so a benefit on top of an adequate diet is not shown.
- BCAA powder: the ISSN protein position stand calls about 1.4 to 2.0 g of protein per kg a day sufficient for most exercising people. If you already eat that much, we see little reason to add BCAAs (our reading).
- Caffeine above 6 mg per kg: the ISSN reports more side effects at about 9 mg per kg and no extra benefit.
- Stacking products on race day: the ISSN says the benefit of combining bicarbonate with caffeine or nitrate is unclear, and every extra product adds a chance of gut trouble.
- Anything new in the last two weeks before the race (our recommendation).
How do I test a supplement before race day?
Treat a supplement as an experiment with one change at a time. The IOC says responses vary between people and that products should be tested in training before competition. The steps below are our recommendation, and they assume your doctor has no objection.
- Name the problem the supplement should solve. If you cannot, skip it.
- Pick one supplement at the studied dose, from a product whose batch was independently tested. Change nothing else about your fuelling that week.
- Try it in a hard session that looks like the race, for example a compromised run session. Write down your stomach, heart rate, sleep and effort.
- Repeat in a second hard session. Drop it if you get gut trouble, tingling you dislike or worse sleep, or if you cannot tell any difference.
- Keep only what you have used at least twice, and plan the pre-race meal around it with the pre-race eating guide.
More on this topic is in the nutrition guides. Carbohydrate and fluid during the race matter more than any supplement here.
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Use the race split calculatorFrequently asked questions
Sources
Published figures are quoted from these pages. Where datasets disagree we say so. Advice marked as our recommendation is not from a source.
- IOC consensus statement: dietary supplements and the high-performance athlete (2018) (accessed 6 November 2026)
- ISSN position stand: caffeine and exercise performance (2021) (accessed 6 November 2026)
- ISSN position stand: safety and effectiveness of creatine supplementation (2017) (accessed 6 November 2026)
- ISSN position stand: beta-alanine (2015) (accessed 6 November 2026)
- ISSN position stand: sodium bicarbonate and exercise performance (2021) (accessed 6 November 2026)
- Dietary nitrate and endurance exercise performance: systematic review and meta-analysis (2021) (accessed 6 November 2026)
- ISSN position stand: protein and exercise (2017) (accessed 6 November 2026)
- Oral branched-chain amino acids supplementation in athletes: systematic review (2022) (accessed 6 November 2026)
HYROX® is a trademark of HYROX World GmbH; IRONMAN® and 70.3® are trademarks of World Triathlon Corporation. Tuffr is not affiliated with or endorsed by these organisers.
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