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Supplements for Sports Performance: The 5 With Good Evidence, and the Doping Risk

For most athletes, caffeine (endurance, strength and sprints) and creatine (strength, with training) have the best evidence: grade A. Beetroot juice (nitrate), beta-alanine and baking soda give small gains in certain events (grade B), and most other products lack good trials. Keep caffeine to 400 mg a day or less; pure caffeine powder can cause a dangerous heartbeat. Some supplements contain banned drugs, so if you are drug tested, ask your anti-doping organisation first.

Published How we grade evidenceEditorial policy

This guide is for adults who train or compete, from weekend runners to tested athletes. If you are under 18, ask a clinician before using any of these.

The short version

  • Caffeine (taken about an hour before, against placebo) improved endurance, strength, muscle endurance, power, jumping and speed across 21 meta-analyses, mostly in young men. Grade A (Grgic 2020). Keep to 400 mg a day or less unless your clinician advises otherwise (FDA).
  • Creatine taken with weight training raised strength more than placebo in adults under 50, mostly in men; it did not help endurance in trained athletes. Grade A for strength (Wang 2024; Fernández-Landa 2023).
  • Nitrate (beetroot juice) gave a small gain against placebo, in tests to exhaustion rather than time trials, and not clearly in well-trained endurance athletes. Grade B (Senefeld 2020; Poon 2025).
  • Beta-alanine taken daily for weeks gave a small overall gain in all-out efforts of 30 seconds to 10 minutes against placebo, clearest in efforts of 4 to 10 minutes. Grade B (Georgiou 2024; Saunders 2017).
  • Sodium bicarbonate (baking soda) helped short, very hard efforts such as 2,000 m rowing, against placebo, but often upsets the gut. Grade B (Grgic 2021).
  • Contamination is a real risk: in one international study, 94 of 634 supplements held anabolic steroids not on the label (Geyer 2004).
Supplement (who, compared with what)What trials foundSize of effectGrade
Caffeine (mostly young men, vs placebo)Better endurance, strength, power, jumps, speedSmall to moderate; larger for enduranceA
Creatine with weight training (adults under 50, vs placebo)More strength gained; no endurance gainSmall; clear in men, not in womenA
Nitrate or beetroot juice (healthy young adults, vs placebo)Longer time to exhaustion; time trials unchangedSmall; not clear in well-trained athletesB
Beta-alanine (trained young men, vs placebo)Small overall gain in all-out efforts; clearest at 4 to 10 minutesSmallB
Sodium bicarbonate (healthy adults, vs placebo)Better sprint tests and 45-second to 8-minute eventsSmall to moderate; gut upset commonB
BCAAs, HMB, glutamine, ketone drinksNo clear performance gainNone foundB (no effect)

What do sports scientists say actually works?

A short list. A 2018 International Olympic Committee (IOC) consensus found good evidence for only a few: caffeine, creatine, buffers such as baking soda and beta-alanine, and nitrate. It puts food, training and a nutrition assessment first, notes that responses vary a lot between people, and advises trying anything in training before using it in competition (Maughan 2018).

Does caffeine improve sports performance?

Grade A: yes, for many kinds of exercise. An umbrella review of 21 meta-analyses (pooled analyses of trials against placebo) found gains in endurance, strength, muscular endurance, power, jump height and speed. The certainty was mostly moderate, the effect was larger for endurance than for short efforts, and most of the people studied were young men (Grgic 2020). In volleyball players, pooled trials found better jumps, agility and attack and serve accuracy on caffeine than placebo (Chen 2025). Energy drinks and pre-workouts that contain caffeine also improved performance in trials (Guest 2021). Our caffeine page also grades aerobic exercise A.

  • Amounts in trials: 3 to 6 mg for each kilogram of body weight, most often about 60 minutes before exercise. Doses as high as 9 mg/kg brought many more side effects without more benefit (Guest 2021). Too much caffeine can raise your heart rate and blood pressure and cause palpitations, anxiety, jitters and poor sleep (FDA). Several of that position stand's authors advise supplement companies, and the society that wrote it takes grants from makers of caffeine products. Upper limit for adults: 400 mg of caffeine a day is the FDA's figure for most adults, an amount it says is not generally associated with negative effects. At the top of the trial range, a heavier adult passes that in one dose, so take more only with your clinician's advice (FDA; check your stack).
  • Heart warning: pure and highly concentrated caffeine powders and liquids can cause a dangerously fast or erratic heartbeat, seizures and death, and a teaspoon is not precise enough to measure a safe serving (FDA). A 39-year-old man died after swallowing about 12 g of pure caffeine powder (Jabbar 2013).

Late caffeine can cost you sleep; our caffeine dependence guide covers cutting back.

Does creatine help athletes?

Grade A for strength when you train with it; no help for endurance. In adults under 50 doing resistance training, creatine raised strength more than placebo: about 4.4 kg more on upper-body tests and 11.4 kg more on lower-body tests. Men gained significantly; in women the extra gain was not significant (Wang 2024). One of its authors has done creatine research sponsored by industry. The IOC adds that it helps repeated short, hard efforts, notes no harmful effects in use of up to 4 years, and warns that the 1 to 2 kg it adds, mostly water, can be a drawback when you must lift your body against gravity, as in jumping events, or make a weight target (Maughan 2018). In 13 studies of trained endurance athletes, creatine did not improve endurance performance (Fernández-Landa 2023).

Creatine raises the creatinine number on blood tests a little without lowering kidney filtration, so tell your clinician before a kidney blood test (Naeini 2025). If you have kidney disease, ask your kidney doctor first. Forms and amounts are on our creatine page.

Does beetroot juice (nitrate) improve endurance?

Grade B: a small gain, mainly in less-trained people. Nitrate, found in beetroot and leafy greens, raises the body's nitric oxide, which affects blood flow and muscle function (Maughan 2018). A 2020 meta-analysis of 80 placebo-controlled crossover studies in young, healthy adults found a small improvement in exercise performance overall. There was no clear effect in studies of well-trained endurance athletes (26 studies) or in the 6 studies of women only (Senefeld 2020).

A 2025 umbrella review re-pooled the trials. Nitrate lengthened time to exhaustion (41 studies) and improved muscle endurance and peak power, but made no difference in time trials (42 studies), the test closest to a race, or in strength. Larger daily amounts taken for more than 3 days did better in the exhaustion tests, and most of the reviews it drew on were of low or critically low quality (Poon 2025). Side effects appear few, though some people get gut upset (Maughan 2018). Our nitrate page also grades endurance B.

Does beta-alanine work?

Grade B: small gains, clearest in hard efforts of 4 to 10 minutes. Beta-alanine builds up carnosine, a buffer in muscle, so it takes weeks of daily use. In 18 placebo-controlled trials in 331 trained young men, it gave a small overall gain in all-out efforts of 30 seconds to 10 minutes; split by length, only the 4- to 10-minute efforts clearly improved, and gains showed by 4 weeks (Georgiou 2024). A larger 2017 review of 40 trials and 1,461 people, some of which also gave baking soda, found a smaller overall effect. Within that 30-second to 10-minute window, tests to exhaustion improved, but timed performance did not clearly improve; the largest effect came from beta-alanine taken with baking soda (Saunders 2017). Our beta-alanine page grades muscular endurance A; timed performance, the result that matters in a race, is less clear, so it gets B here.

  • Amounts in trials: 5.6 to 6.4 g a day gave a benefit in the 2024 review (Georgiou 2024). There is no official upper limit. Tingling skin (paraesthesia) and skin rashes are the known side effects, and the IOC describes trial amounts split into small doses through the day (Maughan 2018).

Does baking soda (sodium bicarbonate) help?

Grade B: for short, very hard efforts, if your gut tolerates it. Baking soda raises the blood's ability to buffer acid. An umbrella review of placebo-controlled meta-analyses found moderate-quality evidence that it improves power in a 30-second sprint cycling test and in the Yo-Yo shuttle-running test. Low-quality evidence supported events of about 45 seconds to 8 minutes, muscle endurance and 2,000 m rowing. It made no clear difference to strength or repeated sprints (Grgic 2021). Our rowing page grades its rowing studies C.

  • Amounts in trials: 0.2 to 0.3 g for each kilogram of body weight, 1 to 3 hours before exercise. Higher doses add no benefit and cause more, and worse, side effects (Grgic 2021b); some of that position stand's authors have done industry-sponsored research. Gut distress is well known at these amounts and can make performance worse rather than better (Maughan 2018). Baking soda is a sodium compound, and its antacid label says to ask a doctor before use if you are on a sodium-restricted diet (DailyMed).

What we'd skip

  • BCAAs (branched-chain amino acids): in 25 studies, they lowered soreness and muscle-damage markers after hard exercise, but muscle performance over the next 2 days was no better than with placebo (Doma 2021). Our BCAA page grades one endurance finding B on three older trials; one of them found no effect on time to exhaustion (van Hall 1995), and the newer pooled evidence above found no performance gain.
  • HMB: no effect on strength or body composition in 6 trials of trained and competitive athletes (Sanchez-Martinez 2018).
  • Citrulline for endurance: no gain in 9 trials (Harnden 2023). For strength and power, 12 small trials pooled to a small benefit, though no single trial showed one on its own (Trexler 2019). Grade C for strength and power.
  • Glutamine: no effect on aerobic performance, immune measures or body composition, though weight fell slightly (Ramezani Ahmadi 2019). Ketone drinks: no difference from placebo in 13 trials (Valenzuela 2020).
  • "Testosterone boosters": only about a quarter of their ingredients had data showing a rise in testosterone, and some products held vitamins and minerals above their upper limits (Clemesha 2020).
  • Big doses of vitamins C and E while you train: fitness improved as much as with placebo over 11 weeks, but muscle markers of training adaptation rose only in the placebo group (Paulsen 2014).
  • Iron and vitamin D unless a test shows you're low: iron raised ferritin (iron stores) mainly in athletes who started very low (Šmid 2024), and extra iron when your stores are adequate can cause vomiting, diarrhoea and abdominal pain, and can progress to haemochromatosis (iron overload) and liver failure (Maughan 2018); in 7 trials, vitamin D did not improve performance (Farrokhyar 2017).
  • Multi-ingredient pre-workouts: in an online survey of 872 regular users, 54% said they had side effects, including skin reactions, heart abnormalities and nausea (Jagim 2019). Some have contained DMAA, which the FDA says is illegal in supplements and can raise blood pressure and lead to heart attack (FDA).

For protein, see our body composition guide.

Can a supplement make you fail a drug test?

Yes. In a study of 634 supplements bought in 13 countries in 2000 and 2001, 94 (14.8%) contained anabolic steroids not on the label, and taking a tiny amount of a nandrolone precursor gave positive tests for several hours (Geyer 2004). A 2026 review put contamination at about 9 to 15% of tested products, mostly stimulants and anabolic agents, found most often in products sold for pre-workout energy, weight loss or muscle (Al-Saad 2026). Among FDA warnings over ten years, 82 of 92 flagged muscle-building products contained steroids or steroid-like ingredients (Tucker 2018).

Under the World Anti-Doping Code, a positive test counts even if the intake was accidental, and can cost medals, records and your place in competition (Maughan 2018). If you are tested, check every product against WADA's Prohibited List and ask your national anti-doping organisation. Batch-testing programmes lower the risk but can't guarantee a clean product; our supplement quality guide explains them.

Safety and interactions

  • Caffeine and medicines: the ciprofloxacin label warns that caffeine can build up while you take that antibiotic (DailyMed), and the antidepressant fluvoxamine slowed caffeine clearance more than tenfold in 7 healthy volunteers (Culm-Merdek 2005). Pre-workouts, energy drinks and gels all add to your total.
  • Baking soda and ADHD medicine: the label for extended-release dextroamphetamine says to avoid stomach alkalinizing agents such as sodium bicarbonate, which raise amphetamine levels (DailyMed). Antacids can interact with other prescription drugs too, so ask your pharmacist (DailyMed).
  • Beetroot juice and blood pressure: in 16 short trials, nitrate and beetroot juice lowered systolic blood pressure by about 4.4 mmHg against placebo (Siervo 2013). If you take blood pressure medicine, ask your prescriber.
  • Heart or kidney conditions: if your heart rhythm is irregular or your blood pressure is high, ask your cardiologist before caffeine or stimulant pre-workouts; with kidney disease, ask before creatine.
  • Under 18: ask a clinician; the amounts in this guide are for adults.
  • Pregnancy: check every one of these, caffeine included, with your midwife or obstetric team.
  • Breastfeeding? Ask your midwife, doctor or a lactation specialist, who can check what passes into breast milk. Caffeine reaches breast milk quickly, and very high intakes have made some babies fussy and jittery (LactMed 2026).

Taking several products at once? Check your stack against the upper limits.

When to see a doctor

  • Chest pain, fainting, or a racing or irregular heartbeat during exercise or after caffeine or a pre-workout: get urgent care.
  • Severe muscle pain and weakness with dark, cola-coloured urine after hard exercise can mean rhabdomyolysis (muscle breakdown that can damage the kidneys): get urgent care.
  • Ongoing tiredness, a drop in performance or missed periods: ask for tests, including iron levels, rather than adding supplements.
  • Don't stop a prescribed medicine on your own; ask the prescriber or pharmacist.

FAQ

Is creatine safe for athletes? In trials, creatine raised the blood creatinine number a little without lowering kidney filtration, and the IOC notes no harmful effects in use of up to 4 years. It adds about 1 to 2 kg of weight, mostly water. People with kidney disease should ask their kidney doctor first.

What is the best supplement stack for athletes? There isn't one. Caffeine and creatine (grade A) have the best evidence; nitrate, beta-alanine and baking soda (grade B) help only in certain events. Each extra product adds side effects and contamination risk.

Do pre-workout supplements work? Pre-workouts that contain caffeine have improved performance in trials, as caffeine does on its own (grade A). In a survey of regular users, more than half said they had side effects, and some products have contained DMAA, a stimulant the FDA says is illegal in supplements.

How much caffeine should I take before a race or game? Trials used 3 to 6 mg for each kilogram of body weight, about an hour before. Most adults should stay at or under 400 mg a day, the amount the FDA cites as not generally linked with harm, and never use pure caffeine powder.

Can a supplement make me fail a drug test? Yes. Lab studies have found banned or unapproved substances, mostly stimulants and steroids, in about 9 to 15% of products tested, and a positive test counts even if it was accidental. Tested athletes should check products with their anti-doping organisation.

Do BCAAs help recovery? They reduced soreness after hard exercise, but muscle performance over the next 2 days was no better than with placebo.

Sources

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