Walk into any supplement shop and there are hundreds of products promising more power, faster recovery and a leaner body. The International Olympic Committee’s expert panel looked at the evidence and found good support for only a handful. Here they are, graded, with who they help, who they don’t, and the risk most people never think about.
The grades in this post: Strong means consistent trial evidence. Moderate means trials agree but the effect is small, or it depends on the event. Mixed means trials disagree, or the effect shrinks in the people who’d care most. Risk marks a safety point.
The short version
- Five have good evidence for performance: caffeine, creatine, nitrate (beetroot), sodium bicarbonate and beta-alanine. That’s essentially the IOC’s list, and the trials since haven’t changed it.
- The effects are real but small. They matter to a competitor chasing a second or a rep. They come a long way behind sleep, training and eating enough.
- Each one helps a particular kind of effort. Bicarbonate and beta-alanine help hard efforts lasting from about 30 seconds to 10–12 minutes. Nitrate seems to help less-trained people more than elite athletes. Matching the supplement to the sport matters more than the brand.
- The risk is contamination. In an international study, about 15% of ordinary supplements contained anabolic steroids that weren’t on the label. For a tested athlete, that can end a career; for anyone, it’s something you didn’t choose to take.
- Try anything in training first, never on competition day.
Where the list comes from
In 2018 the IOC published a consensus statement on supplements for high-performance athletes, written by 25 sports scientists, doctors and anti-doping experts. Their conclusion: nutrition makes “a small but potentially valuable contribution” to performance, supplements make a minor contribution to that, and only a few, “including caffeine, creatine, specific buffering agents and nitrate”, have good evidence of benefits (Maughan 2018). They also said responses vary widely between people, that anything should be trialled in training first, and that a full nutrition assessment should come before any supplement decision.
That last point is the one most people skip. If you’re under-eating, under-sleeping or short of iron, no supplement on this list will make up for it.
The five, graded
| Supplement | What it helps | What the evidence shows | Grade |
|---|---|---|---|
| Caffeine | Endurance most; also strength, muscular endurance, power, sprinting, jumping | An umbrella review of 21 meta-analyses found benefits across a broad range of exercise, larger for aerobic than anaerobic. Quality of evidence was mostly moderate, and most studies were in young men (Grgic 2019). The ISSN position stand calls the benefits “small to moderate”, varying between individuals (Guest 2021). | Strong moderate-quality, consistent |
| Creatine | Short, repeated, high-intensity effort; strength gains alongside resistance training | Across 53 trials, creatine improved upper-body strength in efforts under 3 minutes, regardless of age, sex or training (Lanhers 2017). A 2025 meta-analysis of 69 trials found small gains in bench press (about 1.4 kg) and squat (about 5.6 kg) with resistance training; the effects were clearer in younger adults and men than in older adults and women (Kazeminasab 2025). | Strong for strength with training; smaller and less certain in women and older adults |
| Nitrate (beetroot juice) | Endurance capacity (how long you can keep going) more than race performance | Across 76 trials, nitrate improved time to exhaustion (small to moderate effect) but not time-trial performance (McMahon 2017). A 2026 meta-analysis of 38 studies found a small rise in VO₂max in recreationally active people but no clear effect in highly trained athletes, with signs that small positive studies were over-represented (Qin 2026). No effect on power in interval training across 17 studies (Wong 2021). | Mixed small, and smaller the fitter you are |
| Sodium bicarbonate | Hard efforts of about 30 seconds to 12 minutes; combat sports including boxing; rowing, swimming, running and cycling | The ISSN position stand concludes it improves performance in these efforts, in men and women. Side effects (bloating, nausea, vomiting, stomach pain) can wreck a performance, and part of the effect seems to be placebo (Grgic 2021). One meta-analysis in swimmers found no effect on 200 m time (Huang 2025). | Moderate works for the right event, if your gut tolerates it |
| Beta-alanine | Hard efforts of about 30 seconds to 10 minutes | Across 40 trials (1,461 people), a small overall effect, larger for exercise capacity than for performance, and largest when combined with bicarbonate (Saunders 2017). It takes weeks of daily use to build up in muscle. The only reported side effect is tingling skin (Trexler 2015). | Moderate small effect |
On the sources. The ISSN position stands are written by researchers, several of whom list supplement-industry affiliations on the papers themselves. The IOC panel included anti-doping and medical members. I’ve used the ISSN papers for detail on side effects and timing, and the IOC statement and independent meta-analyses for whether things work. It’s the same standard I’d apply to a drug company’s guideline.
Who it doesn’t apply to
Most of these trials were done in young, trained men in a lab. That matters:
- Women: a 2022 meta-analysis of female athletes found support for caffeine, but “no conclusive effects” for beetroot or creatine on aerobic performance, largely because there are so few studies (López-Torres 2022). That’s absence of evidence, not evidence of absence.
- Older adults: creatine’s strength gains were smaller and less certain (Kazeminasab 2025). There may still be reasons to use it at older ages; that’s covered in The Biochemistry of Structure, my creatine and connective-tissue post.
- If you’re not training hard, the gains here are tiny compared with what training, sleep and food will do. These are finishing touches, not foundations.
The risk you can’t see: contamination
This is the part I’d want every client to know.
- About 15% of non-hormonal supplements bought in 13 countries contained anabolic steroids not declared on the label. Since then, products deliberately spiked with “classic” steroids have been found, and vitamin C, multivitamin and magnesium tablets have been seized that were contaminated with steroids (Geyer 2008). Risk Laboratory testing of products; the 15% figure comes from a 2001–02 study of 634 supplements.
- Why it happens: mostly poor manufacturing (one production line running a steroid product, then your protein), sometimes deliberate adulteration (Maughan 2005).
- Why it matters: in sport, “strict liability” means you’re responsible for whatever is in your sample, whether you knew or not (Maughan 2005). Outside sport, it means taking a hormone you never chose.
- Where it turns up most: of 776 products the US Food and Drug Administration flagged for hidden drugs between 2007 and 2016, most were sold for sexual enhancement, weight loss or muscle building, and 89% of the muscle-building ones contained steroids or steroid-like ingredients (Tucker 2018). Those are the categories promising the biggest effects, and none of them is on the list above.
- What reduces the risk: products batch-tested by an independent anti-doping testing scheme. It doesn’t remove the risk, but it’s the best available.
How much? What the trials used
This is what was tested, not a prescription
The doses below are what the trials and position stands used, mostly in healthy young adults. Body-weight doses are per kilogram; the 70 kg figures are my arithmetic, to make them concrete. If you take medication, have a medical condition, are pregnant, or are under 18, talk to whoever looks after you first.
| What the trials used | Timing | What to know | |
|---|---|---|---|
| Caffeine | 3–6 mg per kg of body weight (210–420 mg at 70 kg). Benefits may start as low as 2 mg/kg; 9 mg/kg added side effects without adding benefit (Guest 2021). | Most often about 60 minutes before; gum works faster (Guest 2021) | The safety level sits at the bottom of the trial range. The European Food Safety Authority found no safety concerns for single doses up to 200 mg (about 3 mg/kg at 70 kg), including within 2 hours before intense exercise in normal conditions, or for habitual intakes up to 400 mg a day in non-pregnant adults; in pregnancy and breastfeeding, up to 200 mg a day (EFSA 2015). For most people, that means the low end of the trial range. Caffeine late in the day costs sleep, and sleep costs more performance than caffeine adds. |
| Creatine (monohydrate) | Either 5 g four times a day (about 0.3 g/kg a day) for 5–7 days, then 3–5 g a day; or simply 3 g a day, which fills the muscles more gradually, over about 28 days (Kreider 2017) | Any time of day; taking it daily matters more than timing | Taken with carbohydrate, or carbohydrate and protein, more is retained (Kreider 2017). Expect a small weight gain, mostly water in the muscle. Creatine raises blood creatinine (by about 0.13 mg/dL, about 11 µmol/L, across 19 trials) without changing eGFR or urea (Tsiaras 2026). Tell whoever orders your blood tests, so a kidney problem isn’t wrongly suspected. With existing kidney disease, ask your doctor first. |
| Nitrate (beetroot juice) | 6.4–12.8 mmol of nitrate (about 400–800 mg), for at least 3 days in a row, gave the most consistent effect (Qin 2026) | Daily for at least 3 days | Look for products that state the nitrate content in mmol or mg (1 mmol of nitrate is 62 mg; my conversion); juices vary. Least likely to help if you’re already highly trained. |
| Sodium bicarbonate | 0.2 g/kg is the minimum that worked; 0.3 g/kg (21 g at 70 kg) seems best. Higher doses add side effects, not benefit (Grgic 2021). | 60–180 minutes before. Or 0.4–0.5 g/kg a day, split across meals, for 3–7 days beforehand, to spare your gut on the day (Grgic 2021) | Test it in training: stomach upset can ruin the event it was meant to help. Smaller doses, taking it about 3 hours before with a high-carbohydrate meal, or enteric-coated capsules reduce side effects (Grgic 2021). It’s a lot of sodium: 21 g of sodium bicarbonate contains about 5.7 g of sodium, more than double the roughly 2.4 g of sodium in the NHS adult maximum of 6 g of salt a day (NHS; my arithmetic). Not for anyone with high blood pressure, heart or kidney disease, or on a salt-restricted diet, without medical advice. |
| Beta-alanine | 4–6 g a day for at least 2–4 weeks; it builds up in muscle, so a single dose does nothing (Trexler 2015) | Daily, split through the day | Tingling skin is the only reported side effect; smaller split doses (about 1.6 g) or slow-release forms reduce it (Trexler 2015). Harmless, but surprising if nobody warned you. |
If you’re a tested athlete: use only products batch-tested by an independent anti-doping scheme, and keep the batch number and receipt.
Where I land
Five supplements earn their place, each for a particular kind of effort. Caffeine is the one with the broadest support. Creatine is the one I’d consider for most people doing resistance training. Bicarbonate and beta-alanine are for specific events, and bicarbonate can backfire. Beetroot helps less the fitter you are.
None of them comes close to sleeping well, eating enough for your training, and training well. If you want to know where you actually stand, that’s a testing and history question first, and a supplement question a long way second.
Next in the series: fuelling, and what happens when you don’t eat enough for what you’re doing. Then making weight for a fight.
Sources
- EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific opinion on the safety of caffeine. EFSA Journal 2015;13(5):4102. doi:10.2903/j.efsa.2015.4102
- Geyer H et al. Nutritional supplements cross-contaminated and faked with doping substances. J Mass Spectrom 2008;43:892–902. PMID 18563865. doi:10.1002/jms.1452
- Grgic J et al. Wake up and smell the coffee: caffeine supplementation and exercise performance — an umbrella review of 21 published meta-analyses. Br J Sports Med 2020;54:681–88. PMID 30926628. doi:10.1136/bjsports-2018-100278
- Grgic J et al. International Society of Sports Nutrition position stand: sodium bicarbonate and exercise performance. J Int Soc Sports Nutr 2021;18:61. PMID 34503527. doi:10.1186/s12970-021-00458-w
- Guest NS et al. International Society of Sports Nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr 2021;18:1. PMID 33388079. doi:10.1186/s12970-020-00383-4
- Huang D et al. Effects of sodium bicarbonate on 200 m time trial performance and physiological responses in swimmers: a systematic review and meta-analysis. Res Sports Med 2025;33:291–307. PMID 39841595. doi:10.1080/15438627.2025.2456630
- Kazeminasab F et al. The effects of creatine supplementation on upper- and lower-body strength and power: a systematic review and meta-analysis. Nutrients 2025;17:2748. PMID 40944139. doi:10.3390/nu17172748
- Kreider RB et al. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. J Int Soc Sports Nutr 2017;14:18. PMID 28615996. doi:10.1186/s12970-017-0173-z (doses from the full text)
- Lanhers C et al. Creatine supplementation and upper limb strength performance: a systematic review and meta-analysis. Sports Med 2017;47:163–73. PMID 27328852. doi:10.1007/s40279-016-0571-4
- López-Torres O et al. Ergogenic aids to improve physical performance in female athletes: a systematic review with meta-analysis. Nutrients 2023;15:81. PMID 36615738. doi:10.3390/nu15010081
- Maughan RJ. Contamination of dietary supplements and positive drug tests in sport. J Sports Sci 2005;23:883–89. PMID 16195040. doi:10.1080/02640410400023258
- Maughan RJ et al. IOC consensus statement: dietary supplements and the high-performance athlete. Int J Sport Nutr Exerc Metab 2018;28:104–25. PMID 29589768. doi:10.1123/ijsnem.2018-0020
- McMahon NF et al. The effect of dietary nitrate supplementation on endurance exercise performance in healthy adults: a systematic review and meta-analysis. Sports Med 2017;47:735–56. PMID 27600147. doi:10.1007/s40279-016-0617-7
- NHS. Salt: the facts. nhs.uk (read 11 October 2026).
- Qin G, Kim S. Effects of beetroot juice supplementation on maximal oxygen uptake during aerobic exercise: a systematic review and meta-analysis. Front Nutr 2026;13:1858216. PMID 42523624. doi:10.3389/fnut.2026.1858216
- Saunders B et al. β-alanine supplementation to improve exercise capacity and performance: a systematic review and meta-analysis. Br J Sports Med 2017;51:658–69. PMID 27797728. doi:10.1136/bjsports-2016-096396
- Trexler ET et al. International Society of Sports Nutrition position stand: beta-alanine. J Int Soc Sports Nutr 2015;12:30. PMID 26175657. doi:10.1186/s12970-015-0090-y
- Tsiaras A et al. The effect of creatine supplementation on kidney function: a systematic review and meta-analysis of randomized controlled trials. J Ren Nutr 2026. PMID 42035842. doi:10.1053/j.jrn.2026.04.010
- Tucker J et al. Unapproved pharmaceutical ingredients included in dietary supplements associated with US Food and Drug Administration warnings. JAMA Netw Open 2018;1:e183337. PMID 30646238. doi:10.1001/jamanetworkopen.2018.3337
- Wong TH et al. The effect of beetroot ingestion on high-intensity interval training: a systematic review and meta-analysis. Nutrients 2021;13:3674. PMID 34835931. doi:10.3390/nu13113674