Runners commonly take a core set of supplements targeting performance, recovery, injury prevention, and nutrient gaps created by high training volumes. The list is shorter than the supplement industry would have you believe, and the evidence behind each one varies considerably. Here’s what actually works, what’s worth considering, and what to know before you spend money.
Caffeine
Caffeine is the most widely used and well-supported performance supplement in endurance sports. It works by blocking the brain’s fatigue signals, lowering your perceived effort so you can sustain a harder pace for longer. The effective dose range is 2 to 9 mg per kilogram of body weight, with around 6 mg/kg showing the best balance of benefit and minimal side effects in research on athletes. For a 70 kg (154 lb) runner, that’s roughly 420 mg, or about four cups of coffee.
Caffeine reaches peak concentration in your blood about 60 minutes after you swallow it, so most runners take it an hour before a race or hard workout. If you’re sensitive to caffeine or rarely drink coffee, start at the lower end of the range. Higher doses don’t necessarily improve performance further and tend to cause jitteriness, a racing heart, or stomach trouble.
Beetroot Juice
Beetroot juice improves running economy, meaning your body uses less oxygen at the same pace. The active ingredient is dietary nitrate, which your body converts into a molecule that widens blood vessels and helps muscles extract energy more efficiently. A dose of 6 to 8 mmol of nitrate, roughly equivalent to 500 ml of beetroot juice or a concentrated shot, has been shown to increase time to exhaustion and improve time trial performance across a range of distances.
Timing matters. Nitrate levels in your blood peak about 2 to 3 hours after ingestion, and the performance benefits appear around 90 to 150 minutes post-dose. One important detail: avoid mouthwash before taking it. The bacteria on your tongue are essential for converting nitrate into its active form, and antiseptic rinses kill them off.
Highly trained elite runners may need a slightly higher dose to see benefits, possibly because their bodies are already so efficient at using oxygen.
Iron
Iron deficiency is one of the most common nutritional problems in distance runners, especially women. Running depletes iron through foot-strike hemolysis (red blood cells breaking down from repeated impact), sweat losses, and gastrointestinal bleeding during long efforts. Low iron means fewer healthy red blood cells carrying oxygen to your muscles, which makes every run feel harder than it should.
If your energy has dropped, your easy pace feels sluggish, or your recovery has worsened, it’s worth getting a blood test that includes ferritin, which reflects your iron stores. Many sports medicine practitioners consider ferritin levels below 30 to 35 ng/mL a concern for athletes, even though general lab reference ranges often list anything above 12 as “normal.” Supplementing without testing first isn’t a great idea, since excess iron can cause its own problems. If you are deficient, your doctor will typically recommend an oral iron supplement taken with vitamin C to boost absorption, and away from coffee or tea.
Vitamin D
Vitamin D plays a direct role in bone health, and runners who log high mileage are already at elevated risk for stress fractures. Research on military recruits and athletes consistently shows that low vitamin D levels increase fracture risk. Recruits with blood levels below 50 nmol/L (20 ng/mL) had significantly more stress fractures. In university soccer players, insufficient vitamin D was associated with a 23-fold increase in fifth metatarsal fractures.
For bone protection, the target is a blood level of at least 30 ng/mL, with some researchers recommending 40 ng/mL or higher for active people. Reaching that level typically requires about 4,000 IU per day of supplemental vitamin D, particularly during winter months or if you train mostly indoors. A simple blood test for 25(OH)D can tell you where you stand.
Protein
Runners need more protein than sedentary people, but less than strength athletes. The International Society of Sports Nutrition recommends endurance athletes consume 1.0 to 1.6 grams of protein per kilogram of body weight per day, with higher-volume and higher-intensity training pushing you toward the upper end. For a 65 kg runner, that translates to roughly 65 to 104 grams daily.
Most runners can hit these numbers through food alone, but protein supplements (whey, casein, or plant-based powders) are useful when whole meals aren’t practical, like immediately after a long run when appetite is low. Spreading protein across the day in 20 to 40 gram servings supports muscle repair better than loading it all into one meal.
Electrolytes and Sodium
Sweat contains sodium in a wide range, roughly 230 to 1,610 mg per liter depending on the individual. Some runners are “salty sweaters” who leave white residue on their clothes, while others lose far less. This variability is why a one-size-fits-all electrolyte plan doesn’t work well.
For runs under 60 to 90 minutes, water alone is usually sufficient. Beyond that, replacing sodium becomes important to maintain fluid balance and prevent the bloated, sluggish feeling of hyponatremia (low blood sodium). Rather than trying to calculate exact losses, most sports dietitians recommend categorizing yourself as a low, moderate, or heavy sodium loser and choosing electrolyte drinks or salt capsules accordingly. If you cramp frequently on long runs, get dizzy despite drinking fluids, or notice heavy salt stains on your gear, you likely fall on the higher end.
Collagen Peptides
Collagen supplements have gained popularity among runners dealing with tendon issues, joint stiffness, or connective tissue injuries. The evidence is promising but specific about how to take it. A study found that 15 grams per day of hydrolyzed collagen, combined with vitamin C and taken 60 minutes before exercise, produced a 153% increase in markers of collagen synthesis compared to placebo. A lower dose of 5 grams didn’t meaningfully outperform placebo.
Vitamin C is not optional here. It’s required for the chemical process that forms the collagen triple helix structure in tendons and ligaments. Taking collagen without it likely reduces the benefit. If you’re dealing with a nagging Achilles, runner’s knee, or plantar fascia issues, the 15 g collagen plus vitamin C protocol before your run is worth trying.
Beta-Alanine
Beta-alanine works by increasing levels of a buffering compound in your muscles that soaks up the acid produced during hard efforts. The burn you feel during a fast 800m or the last kick of a 5K is partly caused by that acid buildup, and beta-alanine helps delay it. The catch is that it requires consistent daily loading, not a one-time pre-race dose. The protocol is 4 to 6 grams daily in divided doses of 2 grams or less, taken for at least 2 to 4 weeks. After four weeks, muscle buffering capacity increases by 40 to 60%.
The performance benefits are strongest for efforts lasting 1 to 4 minutes, making it most relevant for middle-distance runners or those doing high-intensity track workouts. Marathon runners will see less direct benefit. A common side effect is a harmless tingling sensation in the skin, usually on the face and hands, which is why splitting the dose into smaller portions throughout the day helps.
Sodium Bicarbonate
Sodium bicarbonate (baking soda) works similarly to beta-alanine but from the outside of the muscle cell, buffering acid in the bloodstream. The optimal single dose is 0.3 grams per kilogram of body weight, taken about 3 hours before exercise. For a 70 kg runner, that’s 21 grams, roughly 4 teaspoons dissolved in water.
The performance boost is real for high-intensity running, but there’s a significant drawback: gastrointestinal distress. Bloating, nausea, and stomach pain are common. You can reduce these side effects by taking the dose with a high-carbohydrate meal (about 1.5 g carbs per kg of body weight), using enteric-coated capsules that bypass the stomach, or simply using a lower 0.2 g/kg dose. This is not a supplement to try for the first time on race day.
Magnesium
Magnesium is involved in hundreds of metabolic processes including muscle contraction and energy production, and many people don’t get enough through diet alone. Runners often take it hoping to prevent muscle cramps, but the evidence for that specific claim is weak. A Cochrane Review of 11 trials found that magnesium supplementation is unlikely to help with exercise-related cramps at any dose tested.
That said, correcting a genuine magnesium deficiency can improve sleep quality, reduce muscle tension, and support overall recovery. If your diet is low in nuts, seeds, leafy greens, and whole grains, supplementing with 200 to 400 mg of elemental magnesium daily is reasonable. Magnesium glycinate and citrate forms tend to be better absorbed and easier on the stomach than magnesium oxide.
Tart Cherry Juice
Tart cherry juice contains anthocyanins, plant compounds with anti-inflammatory and antioxidant properties. Runners use it primarily to reduce muscle soreness after hard efforts. A typical concentrate serving of 30 ml contains roughly 216 mg of anthocyanins and 605 mg of total phenolics. Some studies show faster recovery of muscle function when cherry juice is consumed both before and after demanding exercise.
The evidence for reducing soreness specifically is more mixed, and the optimal dose hasn’t been nailed down because different products (fresh-frozen juice versus concentrate) vary widely in their active compound content. If you try it, look for a tart cherry concentrate rather than a sweetened cherry juice blend, and take it in the days surrounding your hardest sessions rather than daily.
Creatine
Creatine is best known as a supplement for strength and power, but it has a lesser-known benefit for runners: it enhances glycogen storage when taken with carbohydrates. Glycogen is the primary fuel for sustained high-intensity running, and one study showed that adding 20 grams of creatine per day to a high-carbohydrate diet increased muscle glycogen content within 24 hours, with those elevated stores lasting six days.
The trade-off is weight gain from water retention, typically 1 to 2 kg during a loading phase. For a track runner or someone doing repeat intervals, the extra energy stores may outweigh the added mass. For a marathon runner focused on racing weight, it’s a harder sell. Research on elite cyclists found the creatine-related weight gain didn’t hurt performance on uphill time-to-exhaustion tests, but every runner has to weigh that balance for themselves. A maintenance dose of 3 to 5 grams daily after an initial loading week is the standard protocol.