# Supplements for Endurance Athletes: What Science Really Says

> Which supplements are truly relevant for triathlon, running and cycling? A scientifically grounded overview without the hype.

Endurance athletes face specific challenges: long exercise durations, depleted glycogen stores, electrolyte losses and strain on the immune system. The question is which supplements actually offer a scientifically proven benefit here and which are based more on marketing promises. This article examines the evidence for various supplements in endurance sports.

## Supplements With Proven Effectiveness

For endurance athletes, **carbohydrates** are essential during efforts over 60-90 minutes. An intake of 30-60 g per hour is advisable, with the combination of glucose and fructose in a 2:1 ratio raising the gut's absorption capacity to as much as 90 g/h. **Electrolytes** are equally important, since sweat contains sodium as well as potassium, magnesium and chloride. During long sessions or in the heat, plain water without electrolytes can increase the risk of hyponatremia. **Caffeine** improves endurance performance through reduced pain perception and improved neuromuscular transmission. A dose of 3-6 mg/kg of body weight, taken 30-60 minutes before exercise, is effective.

## Sensible Additions With Good Evidence

**Dietary nitrate** from beetroot juice is converted in the body into nitric oxide (NO), which widens blood vessels and improves oxygen efficiency. This can lower oxygen consumption by 3-5 % at the same power output. A dose of 400-500 mg of nitrate, 2-3 hours before exercise, is recommended. **Omega-3 fatty acids** (EPA and DHA) can modulate the inflammatory responses that arise during high-volume endurance training and thus support recovery. **Iron deficiency** is a common performance-limiting factor, especially among female runners. Regular monitoring of ferritin levels is important, since values below 30 μg/l can impair aerobic performance.

## Supplements With Weak Evidence

Some supplements show only weak or no demonstrable effect for endurance athletes. **BCAAs** (branched-chain amino acids) offer no additional benefit when protein intake is sufficient. **Exogenous ketones** are expensive and their advantage for well-trained endurance athletes is unclear. The evidence for **HMB** (beta-hydroxy-beta-methylbutyrate) in endurance sports is also limited, even though the mechanism of action seems interesting. It is wise to exercise caution with these products and focus on the scientifically grounded options.

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## Frequently Asked Questions

**What role do carbohydrates play during endurance sports?**
Carbohydrates are the primary energy source during efforts over 60-90 minutes. They replenish glycogen stores and prevent a drop in performance. Adequate intake is crucial for maintaining intensity.

**Why are electrolytes important for endurance athletes?**
Electrolytes such as sodium, potassium and magnesium are lost through sweating. They are essential for maintaining fluid balance, muscle function and nerve conduction, helping to prevent dehydration and cramps.

**Can caffeine improve my endurance performance?**
Yes, caffeine can boost endurance performance by reducing pain perception and improving neuromuscular transmission. It should be taken in moderate doses, however, to avoid side effects.

## Sources
Burke LM et al. (2011), Journal of Sports Sciences - Carbohydrates for training and competition.
Jones AM (2014), Sports Medicine - Dietary nitrate and physical performance.
Peeling P et al. (2008), International Journal of Sport Nutrition - Athletic-induced iron deficiency.
Goldstein ER et al. (2010), Journal of the International Society of Sports Nutrition - Caffeine and performance.

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