Supplements for endurance and performance: the few that actually work

Short answer

Out of hundreds of sports supplements, only a handful have good evidence of improving performance. The International Olympic Committee's consensus statement names caffeine, creatine, dietary nitrate (beetroot juice), beta-alanine and sodium bicarbonate as the supplements with strong enough evidence to consider (1):

• Caffeine, 3–6 mg per kilogram of body weight about an hour before exercise, improves endurance, strength and speed for most people (2).

• Creatine, 3–5 g a day, increases strength, power and muscle mass from repeated high-intensity efforts, and may modestly help memory (3, 4).

• Nitrate, from beetroot juice, gives a small benefit in endurance time trials, mostly with regular use and in less-trained people (5).

• Beta-alanine and sodium bicarbonate help in intense efforts lasting roughly 30 seconds to several minutes (6).

Iron improves how tired you feel if you are iron deficient, which is common in female endurance athletes (7). NAD and NMN supplements are heavily marketed, but human trials are small and have not shown convincing gains in muscle or endurance.

Feeling flat in training is not laziness or a lack of grit. Often it is under-recovery, low energy intake, poor sleep or low iron, and no supplement fixes those.

Note: this article is for general education and is not medical advice. Competitive athletes should use batch-tested products, as supplements can be contaminated with banned substances. Stimulant supplements can cause palpitations and raise blood pressure. If you are pregnant, breastfeeding, or have a heart, blood pressure or kidney condition, ask your doctor before using caffeine supplements, pre-workout products or sodium bicarbonate. Call 911 for chest pain, fainting or a rapid, irregular pulse during or after exercise.

Why most sports supplements don't work

Supplements are sold with confident claims, but very few have been tested in well-designed trials in the people who use them. The IOC consensus statement reviewed the evidence and concluded that only a small number of supplements have good evidence of performance benefits, and that even these work only in specific situations (1).

Three other cautions apply to all sports supplements:

• Contamination. Some supplements have been found to contain stimulants or anabolic agents not listed on the label. For tested athletes, an unintentional positive test is still a violation.

• Individual response. Even proven supplements do not work for everyone. Caffeine sensitivity, for example, varies widely.

• Basics first. Enough energy and carbohydrate, protein spread over the day, sleep and a sensible training plan matter far more than any supplement.

The supplements with strong evidence

Caffeine

Caffeine is the most widely used performance supplement, and it works. The International Society of Sports Nutrition concludes that 3–6 mg of caffeine per kilogram of body weight, taken about 60 minutes before exercise, improves performance across many types of exercise, including endurance (2). Lower doses can also help.

Practical points:

• Coffee works, though its caffeine content varies; caffeine gum or tablets give more precise doses.

• Sleep cost. Caffeine taken in the afternoon or evening can disrupt sleep, which undermines recovery.

• Sensitivity varies. Some people feel anxious, shaky or get palpitations at modest doses, and some medicines and health conditions increase sensitivity (8).

• Daily ceiling. The FDA cites 400 mg a day as an amount not generally associated with negative effects in most healthy adults, and pure or highly concentrated caffeine products can be dangerous, even fatal (8). A 3–6 mg/kg dose for a heavier athlete can reach that amount in one serving, so count coffee, gels and pre-workout together.

• Pre-workout powders often contain 200–400 mg of caffeine per scoop plus other stimulants. Best pre-workout is a hugely searched phrase, but most of the effect comes from the caffeine, and some products contain stimulants that are not well studied.

Creatine

Creatine benefits are among the best documented in sports nutrition. Creatine increases the muscle's store of phosphocreatine, which fuels short, intense efforts. The International Society of Sports Nutrition considers creatine monohydrate the most effective supplement for increasing high-intensity exercise capacity and lean body mass, and safe for healthy people when used as recommended (3). The NIH Office of Dietary Supplements describes creatine as safe for short-term use by healthy adults (9); if you have kidney disease or take medicines that affect the kidneys, ask your doctor first.

For endurance athletes, creatine helps less with steady efforts but can support sprints, interval training and recovery between hard sessions. Creatine causes a small gain in body weight from water stored in muscle, which may matter in weight-sensitive sports.

Creatine for brain health is a growing area. A 2024 meta-analysis of 16 randomised trials found creatine improved memory (moderate certainty), with smaller effects on attention and processing speed (4). Our article on creatine for women covers the evidence for women, including bone and muscle.

Nitrate and beetroot juice

Dietary nitrate, found in beetroot juice and leafy greens, is converted in the body to nitric oxide, which can improve the efficiency of muscle oxygen use. A 2022 meta-analysis of 24 studies found that nitrate had a trivial overall effect on time-trial performance of 5–30 minutes, with a small, borderline benefit when taken regularly for several days rather than as a single dose (5). Benefits tend to be smaller in highly trained athletes.

Nitric oxide supplements and citrulline are marketed for "pump" and performance. Citrulline, an amino acid, raises arginine and nitric oxide production; some studies show small benefits in resistance exercise, but evidence is less consistent than for nitrate.

Beta-alanine and sodium bicarbonate

These two supplements help buffer the acid that builds up in muscles during very intense efforts.

Beta-alanine benefits come from raising muscle carnosine, which takes several weeks of daily use. The effect is greatest in efforts lasting about one to four minutes, such as rowing, middle-distance running or repeated sprints. A tingling of the skin is common, especially with larger single doses; the NIH notes it is not a painful, serious or harmful reaction, and beta-alanine appears safe at 1.6–6.4 g a day for up to eight weeks (9).

Sodium bicarbonate (baking soda) is taken before exercise. The ISSN position stand concludes that about 0.2–0.5 g per kilogram of body weight, with 0.3 g/kg often considered optimal, improves performance in intense efforts lasting about 30 seconds to 12 minutes (6). Stomach upset and diarrhoea are common and can ruin a race, so it should be tested in training first. The NIH reports no safety concerns for short-term use of up to 0.3 g/kg (9). Baking soda is also high in sodium, so ask your doctor first if you have high blood pressure or heart or kidney disease.

Iron for endurance athletes

Iron deficiency is common in endurance athletes, especially women, runners and people who eat little meat. Iron is lost through sweat, the gut and, in runners, red blood cell damage from foot strike, on top of menstrual losses.

In a meta-analysis of trials in people with iron deficiency but normal haemoglobin, iron supplements reduced fatigue, but did not improve measured fitness such as VO2max (7). In athletes with true deficiency or anaemia, correcting iron can restore performance. Iron for athletes should be guided by a ferritin test, because unnecessary iron can build up and cause side effects; stomach upset, constipation and nausea are reported at intakes above 45 mg a day (9).

Electrolytes and hydration

Electrolytes benefits depend on how much and how long you sweat. During long or hot sessions, especially over about 90 minutes, replacing sodium and fluid helps maintain performance and prevents low blood sodium (hyponatraemia) from drinking too much plain water. For shorter, cooler sessions, water and normal meals are usually enough. Electrolyte drinks are also used by people with POTS and similar conditions, on medical advice.

Protein for recovery and muscle

Protein supports muscle repair and adaptation to training. Most athletes do well with about 1.2–2.0 g per kilogram of body weight a day, spread across meals, including a portion after training. Protein powder benefits are mostly convenience; food can provide the same protein. Best supplements for muscle growth are, in order of evidence: enough protein, creatine, and training itself.

NAD, NMN and other popular products

NAD supplements and NMN are marketed for energy, endurance and ageing, based on the idea that boosting NAD+ improves cell energy. They do raise NAD+ levels in blood, but human trials are small and short, and they have not shown consistent improvements in muscle mass, strength or endurance in healthy adults. They are expensive and their long-term safety is not established.

Other products with weak or no evidence for performance include branched-chain amino acids (BCAAs) when protein intake is adequate, most "fat burners", testosterone boosters, and many herbal adaptogens. Rhodiola has small studies for mental fatigue with high risk of bias.

Best supplements for recovery is a popular search, but recovery is mostly built from sleep, enough total energy, carbohydrate to refill muscle glycogen after long sessions, and protein. Tart cherry juice and omega-3 fats have small studies on muscle soreness, with mixed results. High-dose antioxidants such as vitamin C and E taken around training may even blunt some of the training adaptations you are working for, so they are not a good everyday habit for athletes. If recovery feels slow week after week, the training load, sleep or food intake is a more likely cause than a missing supplement.

Women and endurance supplements

Women are more likely to be iron deficient and should check ferritin regularly if they train hard. Low energy availability, eating too little for the training load, is a common and underrecognised problem in female athletes and can affect periods, bones, mood and performance. No supplement fixes it. Caffeine metabolism can be slower with some contraceptive pills and in pregnancy.

How to test a performance supplement on yourself

1. Pick one supplement with good evidence for your type of training.

2. Test it in training, never first on race day.

3. Use the doses and timing from studies.

4. Measure something objective: a repeatable time trial, power output or the number of intervals at a set pace.

5. Watch recovery too: sleep, resting heart rate and how you feel the next day.

6. Decide honestly. If there is no measurable benefit after a fair trial, drop it.

Living with training and supplements: the questions people ask next

What is the best supplement for endurance?

Caffeine has the strongest and most consistent evidence for endurance performance, at 3–6 mg per kilogram about an hour before exercise. Dietary nitrate from beetroot juice gives a small benefit, mostly with regular use and in less-trained people. For efforts of one to four minutes, beta-alanine and sodium bicarbonate can help. Iron helps if you are iron deficient. Getting enough carbohydrate and sleep matters more than any supplement.

Is creatine good for endurance athletes?

Creatine helps most with repeated high-intensity efforts, sprints and strength, so it is useful for intervals, team sports and hard training sessions. For steady long-distance efforts, its benefit is smaller, and the water weight gain of about 1–2 kg may be a disadvantage in some sports. It may also help recovery between sessions and has emerging evidence for memory.

Do I need electrolytes when I exercise?

For sessions under about an hour in mild conditions, water is usually enough. For long sessions, heavy sweating or hot weather, electrolyte drinks help replace sodium and reduce the risk of low blood sodium from drinking only water. People with certain medical conditions may be advised to use electrolytes regularly by their doctor.

Is pre-workout safe?

It depends on the product and on you. Many pre-workout products contain high doses of caffeine and other stimulants, which can cause palpitations, anxiety, high blood pressure and poor sleep, and one scoop can use up much of the 400 mg a day the FDA cites for most healthy adults. Some contain ingredients that are poorly studied or not listed. Avoid them if you have heart rhythm problems or high blood pressure, and do not combine them with other caffeine sources.

Do NMN or NAD supplements improve endurance?

Current human evidence does not show consistent improvements in endurance, muscle mass or strength with NMN or NAD-boosting supplements in healthy adults. Trials are small and short. They are expensive and long-term safety is unknown. Training, sleep and nutrition have far more impact.

How do I know if I'm low in iron as an athlete?

Signs include unusual tiredness, poor performance despite training, breathlessness at efforts that used to be easy, a higher heart rate at a given pace, hair shedding, and in women heavy periods. A blood test for ferritin and a full blood count can confirm it. Do not take iron without a test.

Before you blame yourself

When performance stalls, many athletes assume they need to train harder or buy a better supplement. Often the real issue is under-recovery: short sleep, too little food, life stress or low iron. That is not a lack of discipline. It is your body asking for more resources.

Supplements can add a few percent in the right situation. Recovery, fuel and sleep decide whether you can use that few percent at all.

When to see a doctor

See a doctor if you feel unusually tired or your performance drops for weeks despite rest, if you have breathlessness, chest pain or palpitations during exercise, if periods stop or become irregular with training, or before using stimulant supplements if you have a heart condition or high blood pressure.

Call 911 for chest pain, fainting or a rapid, irregular pulse during or after exercise. These are MedlinePlus emergency signs for fast heart rhythms (10).

How to bring this up with your doctor

What to ask for, by name. "Could we check ferritin, full blood count and vitamin D?" For female athletes: "Could low energy availability be affecting my periods or bones?"

What to bring. Your training volume, any supplements with doses, recent performance changes, sleep and, if relevant, your menstrual cycle.

What to say, out loud. "My training has felt much harder for [N] weeks, and my heart rate is higher at the same pace. I'd like to rule out iron deficiency and other causes."

If you're told to rest and see. Ask: "Would a blood test now help us rule out iron deficiency, so I know whether rest alone is the answer?"

How long until you notice a difference? Most supplements take weeks, not days. See how long supplements take to work, and how to tell if one is working.

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How Welltory helps — and what it cannot do

The limits first. Welltory is a general wellness product, not a medical device. It does not measure iron, creatine or caffeine levels, and it does not diagnose overtraining or any condition.

What it can do is show your recovery, which decides whether supplements and training pay off.

Morning readiness. On iOS, Battery starts each morning from your resting heart rate on waking and the quality and quantity of your sleep (Today screen). A resting heart rate above your usual range for several days, together with poor sleep, is worth noticing: it can go with hard training, stress or a coming illness. It is not a diagnosis.

Sleep. Sleep Analysis uses Apple Watch or Oura data on iOS and on Android syncs sleep from Samsung Health, or from Fitbit or Garmin Connect through Health Connect (Sleep Analysis for Android). If you take caffeine before evening training, it is worth checking how you slept that night.

HRV as a trend. If you take morning HRV measurements, take them at the same time after waking, before coffee, in the same position (accurate HRV measurements), and look at weekly trends rather than single days.

Tag sessions and supplements. On iOS, when Welltory marks a stress or rest episode and asks "What happened?", tap, type or talk: "interval session", "pre-workout", "creatine started", "long run in heat". Over weeks, My Patterns shows which tags tend to come with stress and recovery; some sections need a paid plan.

A record for your doctor or coach. From the web app you can export a CSV (Dashboard → choose a chart → Export) (export guide). Patterns are associations to discuss, not proof of what improved your performance.

How we made it

We based this article on the International Olympic Committee consensus statement on dietary supplements and the high-performance athlete (2018), International Society of Sports Nutrition position stands on caffeine, creatine and sodium bicarbonate, meta-analyses of nitrate and endurance performance (2022), creatine and cognition (2024) and iron in non-anaemic iron deficiency (2018), the NIH Office of Dietary Supplements fact sheet on exercise supplements, FDA guidance on caffeine and MedlinePlus emergency signs. Search questions came from what people in the United States most often ask about sports and endurance supplements. For the product section, we checked every function against the Welltory Help Center on October 21, 2026.

Made with AI tools, then edited and fact-checked by the Welltory team. See our Editorial & AI policy.

Jane Smorodnikova, co-founder of Welltory, built the methodology behind how we read physiological data.

Written by Tatsiana Yashyna.

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