The world of sports supplements can be overwhelming. There are hundreds of products promising to boost your performance, speed up recovery or make you faster. The reality is that most runners only need a handful of them, and the rest is marketing (World Athletics).
In this guide we cut straight to the point: which supplements have real scientific evidence behind them, when to use them and which are the best on the market for runners. If you want to dive deeper into general race-day nutrition, check out our race-day nutrition guide.
1. Energy gels
What they are and when to use them
Energy gels are concentrated carbohydrates in liquid or semi-liquid form. Your body can store glycogen for roughly 60-90 minutes of intense running. After that, you need an external energy supply or you'll "bonk" (hit the wall) (Mayo Clinic) (WHO).
When to take them: During races or training sessions longer than 60-75 minutes. Take the first gel at the 30-45 minute mark, then one every 30-45 minutes.
Types of gels and composition
Not all gels are created equal. The carbohydrate composition makes a big difference in absorption and digestive tolerance. The most basic gels contain only maltodextrin, which is absorbed quickly but has an oxidation ceiling of around 60 g/hour through the SGLT1 transporter. More advanced gels use a combination of maltodextrin and fructose (2:1 or even 1:0.8 ratio), which allows two different intestinal transporters (SGLT1 and GLUT5) to work simultaneously, raising carbohydrate oxidation to 90-120 g/hour in trained runners.
Hydrogel-based gels (like Maurten) encapsulate the carbs in a matrix that gels on contact with stomach acid, slowing gastric emptying and reducing digestive issues. They're especially useful for runners who frequently experience gastrointestinal discomfort during races.
Common mistakes with gels
The most frequent mistake is trying gels for the first time on race day. Your digestive system needs to be trained just like your legs. Introduce gels gradually during your long runs in the weeks leading up to the race. Another common error is taking a gel without water: most gels (except isotonic ones like SiS) need a sip of water to be properly diluted in the stomach. Also avoid mixing a gel with an isotonic drink, as the carbohydrate concentration becomes too high and can cause osmotic diarrhea.
Our recommendations:
- SiS Go Isotonic Gel - The easiest to take: no water needed. Liquid texture, mild flavors. Ideal for beginners.
- Maurten Gel 100 - Hydrogel technology that minimizes gastrointestinal issues. The favorite of elite runners. Premium in both price and quality.
- 226ERS Energy Gel - Quality Spanish brand. Great value for money with many flavors. Includes caffeinated versions.
See our complete energy gel guide with the top 10 on the market.
2. Hydration drinks
Isotonic drinks vs electrolytes
When you sweat, you don't just lose water - you lose mineral salts (sodium, potassium, magnesium). Isotonic drinks replace both while also providing carbohydrates for energy. Electrolyte tablets only replace salts, without extra calories (ACSM).
When to use them: During training sessions longer than 45-60 minutes, especially in hot weather. During races, always.
Sodium content: the key to hydration
Sodium is the most important electrolyte during exercise. A good isotonic drink should contain between 300 and 700 mg of sodium per liter. Runners who sweat heavily (salty sweat that leaves white marks on clothing) need drinks in the higher range (500-700 mg/L), while lighter sweaters can stick to the lower range (300-500 mg/L). If you only drink plain water during prolonged efforts, you risk hyponatremia (excessive dilution of blood sodium), which is a potentially dangerous condition.
Hydration plan for race day
A structured hydration plan makes a real difference in performance. The general recommendation is to drink between 400 and 800 ml per hour during the race, adjusting based on temperature, humidity and intensity. Weighing yourself before and after a long run gives you an estimate of your sweat rate: every kilogram lost equals roughly one liter of sweat. The goal is to avoid losing more than 2-3% of your body weight during competition. For more on planning complete race-day nutrition, check out our race-day nutrition guide.
Our recommendations:
- Isostar Hydrate & Perform - The tried-and-true classic. Good taste, correct electrolyte concentration and great price per serving.
- 226ERS Isotonic Drink - Spanish brand with a balanced formula. No artificial colorings. Very well tolerated digestively.
See our complete hydration drinks guide.
3. Recovery shakes and protein
The recovery window
After a hard workout or race, your muscles need to repair themselves. Recovery shakes provide a combination of protein (to repair muscle fibers) and carbohydrates (to replenish glycogen). Traditionally, there's been talk of a 30-60 minute post-exercise "anabolic window" when muscle protein synthesis peaks. Current evidence is more nuanced: if you ate within 3-4 hours before training, that window extends considerably. However, if you trained fasted or many hours have passed since your last meal, consuming protein and carbs as soon as possible after exercise is a priority (PubMed).
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When to use them: After intense workouts, long runs (+90 min) or races. Not necessary after a casual 30-40 minute easy jog.
Types of protein for runners
Whey protein is the most popular due to its rapid absorption and high leucine content, the key amino acid for triggering muscle protein synthesis. Casein is absorbed more slowly and is ideal before bed, providing a steady flow of amino acids overnight. For vegan runners or those with lactose intolerance, pea, rice or soy plant proteins are good alternatives, though it's best to combine several sources to ensure a complete amino acid profile.
How much protein do you need
Endurance runners need between 1.2 and 1.6 g of protein per kilogram of body weight per day. For a 70 kg runner, that means between 84 and 112 grams daily. During high-load periods (marathon prep, peak volume weeks), you can aim for the upper end of the range. Most importantly, spread your intake throughout the day in 4-5 servings of 20-30 g each, rather than concentrating all your protein in a single meal, as the body has a limit of effective absorption per sitting.
Our recommendations:
- 226ERS Recovery Drink - Ideal 3:1 carb-to-protein ratio for runners. Includes essential amino acids and glutamine. Excellent taste.
- Victory Endurance Total Recovery - More affordable alternative with a solid formula. Includes extra vitamins and minerals.
See our complete recovery supplements guide.
4. Key vitamins and minerals
Runners have specific needs for certain micronutrients. These are the ones backed by evidence:
- Iron: Essential for oxygen transport. Runners lose iron through the repeated foot strike impact (hemolysis) and through sweat. Female runners are especially vulnerable to deficiency. If you feel tired for no reason, request a blood test with ferritin levels. A ferritin level below 30 ng/mL can already affect athletic performance, even though the "normal" lab range starts at 15.
- Vitamin D: Crucial for bone health, muscle function and the immune system. If you mostly train indoors or live in areas with little sun (especially in winter), you probably need to supplement. A dose of 1,000-2,000 IU daily is safe for most people. Check out our winter running guide where we dive deeper into the importance of vitamin D during the cold months.
- Magnesium: Involved in muscle contraction and sleep quality. Frequent cramps may indicate a deficit. It's found in nuts, dark chocolate and legumes, but supplementation is safe if you suspect a deficiency. Magnesium citrate is the form with the best absorption.
- Omega-3 (EPA/DHA): Omega-3 fatty acids have anti-inflammatory properties that can speed recovery and reduce post-workout muscle soreness. If you don't eat oily fish at least 2-3 times a week, consider supplementing with 1-2 g of EPA+DHA daily. Look for fish oil supplements with IFOS certification, or algae-based supplements if you're vegan.
- Vitamin C: Beyond its immune function, vitamin C is essential for collagen synthesis and iron absorption. If you supplement iron, taking it alongside vitamin C (a glass of orange juice, for instance) significantly improves absorption. However, excessive doses of vitamin C (over 1,000 mg/day) can interfere with training adaptations, so moderation is key.
5. Caffeine: the most effective legal supplement
Caffeine is arguably the supplement with the strongest scientific evidence for performance improvement in endurance sports. It acts on the central nervous system by reducing perceived effort and delaying fatigue.
- Optimal dose: 3-6 mg per kg of body weight (210-420 mg for a 70 kg runner)
- When: 30-60 minutes before a race or key workout
- Format: Coffee, capsules or caffeinated gels (many brands offer them)
- Expected improvement: 2-4% in performance, which for a half marathon can mean 2-5 minutes
If you're not a regular coffee drinker, start with low doses (100-150 mg) to assess tolerance. Caffeine can cause jitters or gastrointestinal problems in sensitive individuals.
Caffeine tolerance and cycling
If you consume caffeine daily, your body develops tolerance and the ergogenic effect diminishes. A strategy used by many elite runners is caffeine "cycling": reducing or eliminating regular consumption during the 1-2 weeks before an important race to maximize the effect on race day. This can trigger headaches and temporary fatigue during the first 2-4 days of withdrawal, so plan ahead.
Caffeine and sleep
Caffeine has a half-life of 5-6 hours, meaning half the caffeine you consume is still active in your body after 5-6 hours. If you train in the afternoon, avoid caffeinated gels or take the dose as early as possible. Poor sleep quality destroys training adaptations far more than caffeine can improve your performance. For afternoon or evening sessions, opt for caffeine-free gels and save the caffeine for morning races.
6. What you DON'T need
Supplement marketing is aggressive. These are products you can safely skip:
- BCAAs (branched-chain amino acids): If you already consume enough protein (1.2-1.6 g/kg/day), BCAAs add nothing extra. Your body gets them from complete protein.
- L-Carnitine: Marketed as a "fat burner," but the evidence in runners is very weak. Your body produces what it needs.
- Glutamine: Unless you train at a professional level with extreme volumes, your body produces enough.
- Pre-workouts with 10 ingredients: Most are basically caffeine + beta-alanine at an inflated price. A coffee gives you the same effect.
- Collagen: The evidence for preventing joint injuries in runners is very limited and existing studies have significant limitations.
7. Summary table
| Supplement | When to use | Necessary? | Best option |
|---|---|---|---|
| Energy gels | Races/runs +60 min | Yes, for distance | SiS Go Isotonic |
| Isotonic drink | Runs +45 min or in heat | Highly recommended | Isostar Hydrate |
| Recovery shake | Post-intense workout | Recommended | 226ERS Recovery |
| Iron | If deficient (blood test) | Per blood work | Consult your doctor |
| Vitamin D | Year-round if little sun | Likely | 1,000-2,000 IU/day |
| Magnesium | If frequent cramps | Per symptoms | Magnesium citrate |
| Omega-3 | If low oily fish intake | Recommended | 1-2 g EPA+DHA/day |
| Caffeine | Race day | Optional but effective | 3-6 mg/kg |
| BCAAs | - | No | Save your money |
FAQs
Do I need supplements if I only run 3 times a week?
For most recreational runners who train 3-4 times a week, a balanced diet is enough. Gels are only necessary if you run for more than 60-75 minutes straight. The basic supplements that might help you are vitamin D (if you don't get much sun) and iron (if you're a woman). The rest is optional.
When should I take a gel during a race?
Take your first gel between the 30-45 minute mark, before you notice fatigue. After that, one every 30-45 minutes. For a half marathon you'll need 2-3 gels. For a marathon, 5-7. Always take them with water and always test them first during training.
Does caffeine improve running performance?
Yes. Caffeine is the legal supplement with the strongest evidence for performance improvement. 3-6 mg/kg taken 30-60 minutes before exercise can boost your performance by 2-4%. Many gels include caffeine. If you're not used to it, start with low doses.
Are sports supplements safe?
Sports supplements from reputable brands with quality certifications are safe for most people. It's important not to exceed recommended doses, consult a doctor if you take medication, and choose products with quality seals like Informed Sport or NSF Certified for Sport. Avoid buying supplements of dubious origin, without clear labeling or that promise miraculous results.
What supplement should I take before a marathon?
Before a marathon, the most useful supplements are: caffeine (3-6 mg/kg, 30-60 minutes before the start), an energy gel in the minutes leading up to or at the start, and making sure you're well hydrated with electrolytes. During the race you'll need 5-7 gels spaced every 30-45 minutes and isotonic drinks at every aid station. The key is to always practice your nutrition strategy during your long training runs beforehand.
Does collagen help prevent injuries?
Current scientific evidence on collagen for preventing joint injuries in runners is very limited. Some studies suggest a possible benefit for cartilage health when combined with vitamin C, but results are inconclusive and sample sizes are small. Your body naturally produces collagen if you consume enough protein and vitamin C. Before spending money on collagen, prioritize a complete diet and a training plan with proper progression.
How much protein does a runner need per day?
A runner needs between 1.2 and 1.6 grams of protein per kilogram of body weight per day, depending on training volume and intensity. For a 70 kg runner, that means between 84 and 112 grams daily. During high-load periods or marathon preparation, aim for the upper end of the range. Spread your intake across 4-5 meals throughout the day to maximize muscle protein synthesis, with special attention to the post-workout serving.
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