Running faster and longer comes down to training, recovery, and what you put in your body.

Most runners focus on the first two and overlook the third. Supplements occupy a strange space in endurance sports. Some are backed by decades of research. Others amount to an expensive placebo. The Australian Institute of Sport maintains a classification system that separates the useful from the useless, placing supplements into groups based on the strength of available evidence. Group A contains compounds with solid scientific support. This list draws from that category and from peer-reviewed findings on what actually moves the needle for runners.

Fueling Mid-Race Efforts Without Stomach Distress

Gels and chews offer a practical way to maintain carbohydrate intake during longer runs. Products like Gu Energy gels, Clif Bloks, and options to buy Maurten Gel 100 give runners access to fast-absorbing fuel in portable formats. The goal is steady glucose delivery without triggering gastrointestinal problems, which often derail race-day performance.

Some formulations use hydrogel technology to encapsulate carbohydrates, allowing them to pass through the stomach more quickly. Others rely on maltodextrin and fructose blends. Trial during training remains the best method for finding what your gut tolerates at race pace.

Beetroot Juice and Dietary Nitrate

Beetroot juice has earned its place among evidence-backed ergogenic aids. The active compound is dietary nitrate, which the body converts to nitric oxide. This improves oxygen efficiency at the muscular level, allowing runners to maintain pace with slightly less oxygen demand.

A 2025 Sports Medicine umbrella review found that dietary nitrate improved time-to-exhaustion performance. The effects were more pronounced when runners took at least 6 mmol per day for more than 3 days leading into a key effort. Single doses can help, but loading produces better results.

The taste is earthy and strong. Concentrated shots make the dosing easier than drinking large volumes of raw juice. Most products list the nitrate content on the label, which helps with consistency.

Beta-Alanine for Hard Interval Sessions

Beta-alanine buffers hydrogen ions in muscle tissue, which delays the burning sensation that forces runners to slow down during hard efforts. The International Society of Sports Nutrition confirms that 4 to 6 grams daily, taken for at least 2 to 4 weeks, improves exercise performance. The benefits are most pronounced in efforts lasting 1 to 4 minutes, making this supplement well-suited for track workouts, hill repeats, and middle-distance racing.

A common side effect is paresthesia, a tingling sensation on the skin. Splitting the daily dose across multiple smaller servings reduces this.

Beta-alanine does not produce immediate effects. It requires consistent loading over weeks before muscle carnosine levels rise enough to matter.

Iron for Oxygen Transport

Iron deficiency hits runners harder than most athletes. The repetitive foot strike damages red blood cells over time, and sweat losses add up. Women, vegetarians, and high-mileage runners face elevated risk. Research shows that iron deficiency reduces endurance performance by 3 to 4%. Supplementing with 100 mg of elemental iron daily for up to 56 days improved performance by 2 to 20% in deficient athletes. The range is wide because baseline iron status varies.

Blood testing confirms deficiency before supplementation. Taking iron without a deficiency provides no benefit and can cause gastrointestinal distress or accumulation issues. Ferritin levels below 30 ng/mL typically warrant attention in endurance athletes.

Vitamin D Supports Muscle Function

Low vitamin D levels affect muscle strength, power output, and endurance capacity. Runners who train indoors, live in northern latitudes, or avoid sun exposure run higher deficiency risk. Recommended serum levels sit above 32 ng/mL, with preferred levels above 40 ng/mL for athletes. A blood test determines where you fall. Supplementation doses depend on how low the baseline reading is. Most people respond to 1000 to 4000 IU daily, though severely deficient runners may need higher loading doses under medical supervision.

Vitamin D works slowly. Levels take weeks to rise, so winter supplementation should start in autumn for runners concerned about seasonal drops.

Putting This Together

Supplements work best when basic nutrition is already solid. Caffeine and beetroot juice offer acute performance benefits on race day. Beta-alanine and vitamin D require weeks of consistent intake. Iron supplementation depends entirely on blood work. None of these replace proper training, adequate sleep, or sensible pacing strategy. They provide small edges that compound over time and across repeated efforts. For runners looking to squeeze out additional performance, these 5 options carry the strongest research support.