Understanding Nutritional Demands of Endurance Training

Endurance athletes — runners, cyclists, triathletes, swimmers — place unique demands on their bodies. Prolonged exercise depletes glycogen stores, increases oxidative stress, causes muscle microtrauma, and elevates inflammatory markers. Meeting these demands through food alone can be challenging, which is why many athletes turn to supplementation.

However, not all supplements marketed to endurance athletes have robust evidence. This guide separates well-studied options from those with limited or conflicting data.

Supplements With Strong Evidence

Carbohydrate-Electrolyte Solutions

During exercise exceeding 60–90 minutes, consuming 30–60 g of carbohydrate per hour (up to 90 g with mixed transporters) maintains blood glucose and spares glycogen. Sodium (300–600 mg/hour) replaces sweat losses and supports fluid retention. This is the most consistently supported ergogenic aid for endurance performance.

Caffeine

Doses of 3–6 mg/kg body weight, taken 60 minutes before exercise, reliably improve time-trial performance and reduce perceived exertion. Individual response varies; some experience GI distress or sleep disruption. Habitual users may have attenuated benefits.

Beta-Alanine

Chronic loading (4–6 g/day for 4+ weeks) increases muscle carnosine, buffering hydrogen ions during high-intensity efforts lasting 1–4 minutes. Benefit for pure long-duration endurance is less clear. Paresthesia (tingling) is a harmless but common side effect.

Nitrate (Beetroot Juice)

Dietary nitrate converts to nitric oxide, reducing the oxygen cost of submaximal exercise. Effects are most consistent in recreational athletes; elite responses are variable. Typical protocol: 300–600 mg nitrate 2–3 hours pre-exercise.

Supplements With Moderate or Context-Dependent Evidence

Creatine Monohydrate

While primarily associated with power sports, creatine may benefit endurance athletes by improving interval training quality, supporting glycogen resynthesis when co-ingested with carbohydrate, and reducing muscle damage during high-intensity blocks. Standard dose: 3–5 g/day.

Iron

Iron deficiency (with or without anemia) impairs oxygen transport and mitochondrial function. Supplementation only benefits those with low ferritin (