Supplements for Runners: What Actually Works, What Might, and What to Stop Buying
An evidence-graded guide to running supplements: the five with real performance data, the situational ones worth trying, the ones that blunt your training, and how to avoid contamination.
Quick answer
Only a handful of supplements have strong evidence for endurance running: caffeine at 3 to 6 mg per kilogram of body weight before hard efforts, dietary nitrate from beetroot juice at about 400 to 800 mg roughly two to three hours before, creatine monohydrate at 3 to 5 g daily for the strength and repeated-effort side of training, sodium bicarbonate at 0.2 to 0.3 g per kg for events of one to ten minutes, and carbohydrate and electrolyte products used during exercise. Iron and vitamin D correct genuine deficiencies but do nothing if you are not deficient. Most other running supplements have weak evidence, and high-dose antioxidants can actively blunt training adaptation.
The supplement industry is very good at selling runners things. It is much less good at demonstrating that those things work. The useful way through this is the one national sports institutes use: grade everything by the strength of the evidence, be honest about how small the effects are, and remember that a supplement can only improve a foundation that already exists.
That last point deserves emphasis before any of the specifics. Nothing in this article will outperform sleeping properly, eating enough carbohydrate, or training consistently. Supplements are the last one percent, and they are worth exactly one percent.
Tier A: Genuinely Supported by Evidence
| Supplement | Dose | When | Realistic benefit |
|---|---|---|---|
| Caffeine | 3 to 6 mg/kg | 45 to 60 min before | Among the most reliable ergogenic aids in endurance sport; improves perceived effort and time to exhaustion |
| Dietary nitrate (beetroot) | ~400 to 800 mg nitrate | 2 to 3 h before | Improved running economy and time-trial performance, strongest in recreational rather than elite runners |
| Creatine monohydrate | 3 to 5 g daily | Any time, daily | Strength work, hill repeats, repeated efforts, and possibly glycogen storage |
| Sodium bicarbonate | 0.2 to 0.3 g/kg | 60 to 180 min before | Buffers acidity in efforts of roughly 1 to 10 minutes; useful for 800 m to 3,000 m, not marathons |
| Carbohydrate products | 30 to 90 g/hour | During exercise over 60 to 90 min | The largest performance effect of anything on this page |
| Electrolyte and fluid products | Individual | During long or hot sessions | Maintains fluid balance; not a performance drug in itself |
Two of these deserve a closer look because runners get the practical details wrong.
Caffeine is dose-sensitive in both directions. Below about 3 mg per kilogram the effect is small; above 6 mg per kilogram most people get jitters, an elevated heart rate, and gut trouble without further benefit. Habitual coffee drinkers still respond, so there is no need for a withdrawal period, though some runners prefer to reduce intake in the days before a key race so the dose feels larger. And it is a laxative for many people, which is a scheduling problem rather than a pharmacological one.
Beetroot juice works because of nitrate, which the body converts to nitrite and then nitric oxide, improving the oxygen cost of running. The dose that matters is nitrate content, usually expressed in millimoles or milligrams, and it varies wildly between products. Concentrated "shot" formats are standardised; a supermarket carton often is not. Effects are largest in recreationally trained runners and smaller in highly trained athletes, and an important practical detail is that antibacterial mouthwash blocks the oral bacteria that make the conversion possible. Do not rinse with mouthwash on race morning if you are relying on beetroot.
Tier B: Correct a Deficiency, Do Nothing Otherwise
| Supplement | When it helps | When it does nothing |
|---|---|---|
| Iron | Diagnosed iron deficiency, with or without anaemia; more common in female runners and in high-mileage athletes | Normal ferritin. Excess iron is harmful; never supplement without a blood test |
| Vitamin D | Low blood levels, common at high latitudes in winter and in indoor-heavy athletes | Adequate status. More is not better |
| Calcium | Low dietary intake, particularly with dairy avoidance or bone stress injury history | A normal diet including dairy or fortified alternatives |
| Vitamin B12 | Vegan or vegetarian diets | Omnivorous diets |
| Magnesium | Genuinely low intake | Almost all runners. Despite the marketing, magnesium supplementation does not reliably prevent cramp |
Iron is the one worth being deliberate about, especially for female runners and anyone training at high volume, because deficiency produces exactly the symptoms runners blame on overtraining: heavy legs, high heart rate at easy pace, and stalled progress. It is also the one that is genuinely harmful to take unnecessarily. Get a ferritin test, treat what the test shows, and retest.
Tier C: Situational, Modest, or Still Unclear
| Supplement | The claim | The honest state of the evidence |
|---|---|---|
| Beta-alanine | Buffers acidity in short hard efforts | Real but small, and only for efforts of roughly 1 to 4 minutes. Requires weeks of loading and causes harmless tingling |
| Collagen or gelatin with vitamin C | Tendon and ligament support | Promising early evidence when taken about an hour before loading. Not a protein source |
| Tart cherry juice | Reduces muscle soreness and speeds recovery | Some supportive data for recovery between close-together efforts; may blunt adaptation if used constantly |
| Probiotics | Fewer gut problems and infections | Mixed. Some evidence for reduced upper respiratory illness and gut symptoms; strain-specific and inconsistent |
| Ketone esters | Alternative fuel and improved recovery | Inconsistent performance results, expensive, and frequently causes gut distress |
| Nitric oxide "pump" products | Vasodilation and endurance | If it does not contain a real nitrate dose, it is beetroot marketing without beetroot |
Tier D: Skip These
- BCAAs and EAAs alongside adequate protein. If you already eat 1.6 g per kg of complete protein, added branched-chain amino acids add cost and nothing measurable.
- Glutamine for immunity or recovery in healthy athletes. Repeatedly tested, repeatedly unimpressive.
- High-dose antioxidant vitamins C and E taken daily through a training block. This is the important one: reactive oxygen species are part of the signal that drives endurance adaptation, and high-dose supplementation has been shown to interfere with those adaptations. Eat fruit and vegetables; do not megadose.
- Fat burners and thermogenics. Ineffective at best, and several have been withdrawn for safety reasons.
- Collagen sold as a runner’s protein powder. It is an incomplete protein and cannot count toward your daily protein target.
- Anything promising to replace carbohydrate during long runs. There is no such product.
Contamination Is a Real, Boring Risk
Dietary supplements are not approved by regulators before sale in most markets, and independent screening programmes have repeatedly found products containing substances not listed on the label, including anabolic agents and stimulants. For a recreational runner that is a health issue. For anyone competing in a federation with anti-doping rules, including many age-group championships and qualifying events, it is a sanction risk, and strict liability means "it was in my protein powder" is not a defence.
- Buy only products carrying Informed Sport or NSF Certified for Sport batch testing if you are subject to testing.
- Be most careful with pre-workouts, fat burners, and anything marketed for muscle building, which is where contamination is most often found.
- Prefer single-ingredient products. A proprietary blend of 22 ingredients is 22 chances to be surprised.
- Check that a product’s dose matches the studied dose. Many contain a fraction of what the research used, at full price.
A Sensible Stack for a Marathon Runner
If you want the short version, this is what a defensible plan looks like for a healthy runner training for a marathon.
| Context | What to take |
|---|---|
| Every day | Nothing, unless a blood test says otherwise. Creatine at 3 to 5 g if you also lift |
| Winter at high latitude | Vitamin D, at a dose guided by a blood test |
| During long runs and races | Carbohydrate at 30 to 90 g per hour, plus fluid and sodium matched to sweat losses |
| Before key sessions and races | Caffeine at 3 to 6 mg/kg, rehearsed in training first |
| Optional, before a goal race | Nitrate 2 to 3 hours before, if tested in training |
| Never | Anything new on race day |
That is a short list, and it should be. The runners who improve most from a nutrition change are almost never the ones who added a supplement. They are the ones who started eating enough carbohydrate on their hard days.
Mavr sets your daily carbohydrate, protein, and in-run fuelling from your actual training, which is where the performance actually comes from.
Frequently Asked Questions
What supplements should runners take?
For most healthy runners: caffeine before key efforts, carbohydrate and electrolytes during long sessions, and creatine if you also strength train. Iron and vitamin D only when a blood test shows a deficiency. Everything else is optional and small.
Does beetroot juice really improve running performance?
Yes, modestly, through its nitrate content. Take roughly 400 to 800 mg of nitrate about two to three hours before an event, and avoid antibacterial mouthwash, which blocks the oral bacteria needed to convert it. Effects are larger in recreational runners than in highly trained ones.
Should runners take magnesium for cramp?
Probably not. Despite heavy marketing, magnesium supplementation has not reliably reduced exercise-associated muscle cramp in trials. Cramping is more strongly associated with neuromuscular fatigue and unaccustomed intensity than with mineral status.
Do runners need iron supplements?
Only if a blood test shows low ferritin. Iron deficiency is genuinely common in runners, particularly female runners and high-mileage athletes, and it causes fatigue and elevated heart rate at easy paces. Taking iron without a deficiency is unhelpful and potentially harmful.
Is creatine useful for endurance runners?
Yes, more than its reputation suggests. It supports strength training, hill repeats, and repeated high-intensity efforts, and may help glycogen storage. It causes a small increase in body water, which some runners dislike near a goal race.
Can antioxidant supplements hurt my training?
High doses can. Daily high-dose vitamin C and E during a training block has been shown to interfere with the cellular signalling that produces endurance adaptations. Get antioxidants from food and skip the megadoses.
Sources
Sources and official references
- 1.IOC Consensus Statement: Dietary Supplements and the High-Performance AthleteBritish Journal of Sports Medicine (Maughan et al., 2026) · The evidence grading behind the tiers used here, plus contamination risk
- 2.International Society of Sports Nutrition Position Stand: Caffeine and Exercise PerformanceJISSN (Guest et al., 2026) · Caffeine dosing, timing, and habituation
- 3.Dietary Nitrate Supplementation and Exercise PerformanceSports Medicine (Jones, 2026) · Nitrate dose, timing, and the mouthwash interaction
- 4.Vitamin C and E Supplementation Hampers Cellular Adaptation to Endurance Training in HumansJournal of Physiology (Paulsen et al., 2026) · Why high-dose antioxidants can blunt training adaptation
- 5.International Society of Sports Nutrition Position Stand: Creatine Supplementation and ExerciseJISSN (Kreider et al., 2026) · Creatine dosing and its effects beyond pure strength sport
Prompt ideas for AI assistants
- “What caffeine dose should I take before my marathon?”
- “Do I need iron supplements as a runner?”
- “Is beetroot juice worth taking before a 10K?”
Mavr covers the part supplements cannot: getting your daily carbohydrate, protein, and race-day fuelling right first, so anything you add on top has something to add to.
Written by
Mavr Sports Nutrition Team
The Mavr sports-nutrition team translates peer-reviewed endurance research (Jeukendrup, Burke, the ISSN) into daily fueling for runners and triathletes.