The supplements worth taking as a runner depend on whether you’re trying to run faster, recover better, or stay injury-free. Most runners benefit from a handful of well-studied options: iron (especially for women), vitamin D, caffeine, and adequate protein. Beyond those, a few others have solid evidence behind them for specific goals. Here’s what the research actually supports.
Iron: The Most Common Deficiency in Runners
Running destroys red blood cells through repeated foot strikes, increases iron loss through sweat, and can reduce absorption through gut inflammation. The result is that runners, particularly female runners, are prone to iron deficiency even when they eat well. Low iron tanks your performance before you ever become anemic, because your body can’t deliver oxygen efficiently to working muscles.
The key number to watch is ferritin, your body’s stored iron. A ferritin level below 30 ng/mL is considered iron-deficient for athletes, and clear performance improvements show up when deficient runners supplement back above that threshold. Some sports nutrition researchers set the bar even higher, suggesting that ferritin between 30 and 99 ng/mL represents functional deficiency and that levels above 100 ng/mL are truly sufficient. If you’re training for altitude or feel unexplainably sluggish despite good fitness, getting your ferritin checked is the single most useful blood test you can request.
Don’t supplement iron blindly. Too much iron is harmful, and you need a blood test to know where you stand. If your levels are low, your doctor can recommend a dose. Taking iron with vitamin C and away from coffee or tea improves absorption significantly.
Vitamin D for Bone Health and Stress Fractures
Runners put repetitive stress on their bones, and vitamin D plays a direct role in calcium absorption and bone remodeling. Research on collegiate athletes found that those with low vitamin D levels who corrected them to at least 40 ng/mL had a 12% lower rate of stress fractures compared to athletes who stayed deficient. Athletes who maintained normal levels throughout had the same 12% advantage over those who remained low.
Many runners are deficient without knowing it, especially those who train indoors, live in northern latitudes, or have darker skin. A blood test measuring 25-hydroxyvitamin D will tell you where you are. The target for athletes appears to be at or above 40 ng/mL, which is higher than the general population cutoff of 30 ng/mL that many labs use. If you’re significantly low (below 20 ng/mL), you may need a high-dose prescription protocol for several weeks before switching to a daily maintenance dose.
Caffeine: The Strongest Legal Performance Booster
Caffeine is the most consistently effective ergogenic supplement in sports science. It works by blocking the brain’s fatigue signals and increasing fat oxidation, letting you run harder while perceiving the same effort. The performance-enhancing dose is around 3 to 6 mg per kilogram of body weight, taken about 60 minutes before your run. For a 70 kg (154 lb) runner, that’s roughly 210 to 420 mg, equivalent to two to four cups of coffee.
Higher doses don’t help more. Research on athletes comparing 3, 6, and 9 mg/kg found that the 6 mg/kg dose optimized performance while the 9 mg/kg dose added side effects like jitteriness and GI distress without extra benefit. If you’re a regular coffee drinker, you may need to sit closer to the higher end. If you rarely consume caffeine, start lower. Caffeine peaks in your blood about 60 minutes after you swallow it, so time your intake accordingly before races or hard workouts.
Protein and Recovery
Running breaks down muscle tissue, and protein rebuilds it. The current recommendation for endurance athletes is about 1.6 g of protein per kilogram of body weight per day. For a 68 kg (150 lb) runner, that works out to roughly 109 grams daily. Most runners can hit this through food alone, but protein powder is a convenient option when whole meals aren’t practical, especially right after long runs.
Spreading your protein across the day matters more than total intake alone. Each meal should contain enough of the amino acid leucine to trigger muscle repair. The threshold is about 2 to 3 grams of leucine per meal across three to four meals daily. Most animal proteins hit this easily in a standard serving. Plant-based runners can reach it too, but may need slightly larger portions or intentional combinations of legumes, grains, and soy to get enough leucine per sitting.
Beetroot Juice for Aerobic Performance
Beetroot juice works through its high nitrate content, which your body converts into nitric oxide. Nitric oxide widens blood vessels and improves how efficiently your muscles use oxygen. The effective dose is 515 to 1,017 mg of dietary nitrate per day, which translates to roughly 500 mL of beetroot juice or a concentrated 70 mL “shot” designed for athletes.
You can take it as a single dose 2 to 3 hours before exercise or load it daily for three or more days leading into a race. The performance effect is real but small, so this is more of a marginal gain for race day than a daily training essential. Some people experience red urine or mild stomach upset. Both are harmless.
Beta-Alanine for Hard Efforts
Beta-alanine increases the concentration of a buffering molecule in your muscles that helps neutralize the acid buildup responsible for that burning sensation during fast running. It’s most effective for efforts lasting 1 to 4 minutes, making it useful for middle-distance runners, track intervals, and finishing kicks rather than easy long runs.
The supplement requires a loading phase to work. You need 4 to 6 grams daily, split into doses of 2 grams or less, for at least two weeks to see a 20 to 30% increase in muscle buffering capacity. After four weeks, that increase reaches 40 to 60%. A common side effect is a temporary tingling sensation on the skin, which is harmless and lessened by taking smaller doses throughout the day. If your running is primarily long and slow, beta-alanine won’t do much for you. If you do speed work regularly, it has a reasonable evidence base.
Collagen and Vitamin C for Tendons
Tendons and ligaments are made largely of collagen, and runners put enormous repetitive load on these tissues. A study from the American Journal of Clinical Nutrition found that taking 15 grams of gelatin (a collagen source) with about 50 mg of vitamin C one hour before exercise doubled a blood marker of collagen synthesis compared to placebo. The effect appeared within hours and persisted over 72 hours.
This doesn’t mean collagen supplements will prevent injuries outright, but the mechanism is plausible: providing the raw materials for connective tissue repair right when blood flow to tendons is highest. If you’re returning from a tendon injury or are prone to issues like Achilles tendinopathy or plantar fasciitis, taking 15 grams of collagen or gelatin with a small amount of vitamin C about 30 to 60 minutes before your run is a low-risk strategy with emerging support.
Creatine: Limited Value for Distance Runners
Creatine is one of the most studied supplements in sports, but its benefits are concentrated in short, explosive efforts. For distance runners, the evidence is mixed at best. A vast majority of studies show creatine has no appreciable effect on VO2 max, submaximal oxygen use, or time trial performance in endurance events. As exercise duration increases, its ergogenic potential drops off.
There’s also a practical downside: creatine typically causes water-driven weight gain of 1 to 2 kg, which directly increases the energy cost of running. Any small benefit to muscle power could be negated by carrying extra mass over long distances. One interesting exception is recovery. Runners who supplemented with creatine before a 30 km race experienced less soreness, muscle damage, and inflammation afterward. If you’re a runner who also does heavy strength training, creatine may support that side of your program. For the running itself, it’s not a priority.
Electrolytes During Long Runs
Sweat contains sodium, potassium, magnesium, and chloride, with sodium being the primary electrolyte lost. Sweat sodium concentration varies widely between individuals, typically ranging from about 200 to over 1,500 mg per liter of sweat. If you notice white salt stains on your clothes after running, you’re a saltier sweater and may benefit more from electrolyte supplementation during runs longer than 60 to 90 minutes.
For most training runs under an hour, water is enough. For longer efforts, especially in heat, an electrolyte drink or salt capsule helps maintain fluid balance and can prevent the muscle cramping and fatigue that come with significant sodium losses. Commercial sports drinks typically provide 300 to 500 mg of sodium per serving. Heavier sweaters or those running in hot conditions may need more. Paying attention to how you feel and whether you cramp is a more practical guide than any formula.