Every endurance athlete, recreational or professional, is looking for ways to improve their body’s ability to perform or recover. While a smart training plan, balanced diet, and routine recovery habits (and maybe a bit of genetics) are the true magic behind athletic success, many turn to supplements to help get the most out of their efforts.
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A strategic, balanced diet of nutrient-rich, minimally processed foods should always form the foundation of health and performance. Still, supplements can play a targeted role in helping athletes meet the intense physiological demands of long-distance training and competition. From supporting energy production and improving blood flow to aiding muscle repair, the right evidence-based supplements can help bridge nutritional gaps and optimize performance. Used thoughtfully—not as shortcuts, but as tools—supplements become part of a comprehensive strategy that allows endurance athletes to train harder, recover faster, and perform consistently at their peak.
As any governing body does not closely regulate supplements, and many are considered banned substances by the World Anti-Doping Agency, it is crucial to do some homework before you begin taking these substances. Make sure you are taking supplements that carry the NSF label, which means they have been third-party approved and monitored and are approved for sports.
While thousands of supplements are available, only a few are truly beneficial for endurance athletes. Here are supplements that every endurance athlete should consider taking.
Multivitamin
Sounds basic, but this supplement helps ensure that an athlete has the basics necessary for normal health function. Nutrients such as vitamins and minerals are essential in metabolic pathways and cellular functions related to energy production, recovery, immunity, and tissue function. Since endurance athletes place high demands on these areas, it makes sense that they need to maintain a solid nutrient foundation to perform day after day. Taking a multivitamin appropriate for age and gender is the most basic way to reduce the gap between dietary intake and needs.
Vitamin C
Exercise is stressful for the body. Vitamin C is a powerful antioxidant that helps reduce oxidative stress produced during prolonged aerobic exercise. By helping neutralize these molecules, vitamin C may support recovery and immune function during heavy training periods. It also facilitates the absorption of iron, another crucial nutrient for endurance athletes' performance. A meta-analysis of 18 randomized controlled trials found that vitamin C supplementation significantly reduced exercise-induced oxidative stress and inflammatory markers (such as IL-6) following intense exercise bouts. Look for liposomal vitamin C for increased absorption.
Creatine
Creatine helps replenish ATP, the body’s primary energy source for short, high-intensity efforts. Endurance performance is not directly affected by creatine; by improving the rate of muscle recovery, creatine can help endurance athletes bounce back from repeated high-intensity bursts such as hill climbs, surges, or sprint finishes. Creatine also improves brain energy, allowing endurance athletes to keep up mental toughness as the miles go on. This substance is found naturally in animal protein foods; however, for athletes following animal-free diets, supplementation could be warranted. Female and master’s athletes can reap the biggest benefits from taking 4grams a day in supplement form.
Caffeine
Caffeine is one of the most widely used and studied legal ergogenic aids for endurance athletes. It stimulates the central nervous system, increases alertness, and reduces perceived fatigue, allowing athletes to sustain effort for longer periods. It may also enhance fat utilization and delay glycogen depletion during endurance exercise. A meta-analysis of 21 studies found that caffeine ingestion reduced perceived exertion ratings by about 5.6% and improved exercise performance by about 11.2% compared with a placebo. This supplement requires attention to timing, as it can take roughly 20 minutes to kick in and negatively affect sleep.
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Sodium Bicarbonate
Sodium bicarbonate acts as a buffering agent, helping neutralize hydrogen ions produced during high-intensity exercise. This buffering effect delays the onset of muscle acidosis and fatigue, helping athletes maintain higher intensities during surges, intervals, or sprint finishes in endurance events. Clinical trials found that sodium bicarbonate supplementation significantly improved time to exhaustion during exercise, suggesting a meaningful performance effect.
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Iron
Iron is a critical mineral for endurance performance because it is a key component of red blood cells, which transport oxygen to working muscles, supporting aerobic metabolism and endurance capacity. Endurance athletes—especially runners and female athletes—are at higher risk of iron deficiency due to sweat loss, gastrointestinal bleeding, and foot-strike hemolysis (crushing red blood cells with each step). A study of over 1,100 athletes found that those with iron deficiency had significantly lower VO₂ peak values and were less likely to reach high aerobic capacity levels, demonstrating the importance of adequate iron for endurance performance. Before supplementing, get labs drawn by a physician.
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Gels, sport drinks, etc
Many endurance athletes think of these as a food group, but they are indeed supplements. These items provide a concentrated source of easily digestible carbohydrates that can be rapidly absorbed during exercise. Endurance athletes help maintain blood glucose levels and provide a quick energy source when muscle glycogen stores decline, while sparing muscle protein for energy. Having a carbohydrate source continually throughout performance delays fatigue and helps sustain pace during prolonged endurance activity. A randomized controlled trial found that consuming a carbohydrate gel during prolonged intermittent running improved endurance performance compared with a placebo.
Honorable mention goes to BCAA, nitrates, and collagen. These supplements are a bit more niche and might not be appropriate or useful for all athletes. For example, consuming beetroot supplements to increase nitrate levels can get your blood flowing and deliver more oxygen to muscles in need. However, this tends to benefit new or recreational athletes with a higher performance ceiling more than well-trained athletes. If you are looking for every improvement possible, it might be worth digging deeper into these to see whether they would be appropriate for your athletic needs and budget.
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