Several supplements appear to be helpful for endurance including caffeine, dietary nitrates, and beta-alanine.
Caffeine has been shown to improve endurance performance, spare glycogen, promote fat oxidation, reduce fatigue, and decrease perceived effort when consumed prior to exercise in doses ranging from 3-9 mg/kg body weight .
Nitrates in the form of beetroot juice may also assist with endurance performance. Consuming nitrates prior to exercise enhances vasodilation, blood flow, glucose uptake, and muscle contraction and relaxation, resulting in improved muscle function, cardiorespiratory capacity, and time trial performance, particularly in non-elite athletes . Research shows that consuming 300-600mg of nitrates 90 minutes before endurance exercise helps reduce the oxygen cost of exercise, increases time to exhaustion, and improves VO2max .
Beta-alanine is a non-essential amino acid that has been shown to buffer lactic acid production and assist with endurance exercise. One trial showed that 5g/day beta-alanine supplementation improved 10K running time and reduced lactate concentration in active adults . Other studies on beta alanine for endurance performance have yielded similar results.
1. Vitale, K., & Getzin, A. (2019). Nutrition and Supplement Update for the Endurance Athlete: Review and Recommendations. Nutrients, 11(6), 1289. https://doi.org/10.3390/nu11061289
2. Santana, J. O., de Freitas, M. C., Dos Santos, D. M., Rossi, F. E., Lira, F. S., Rosa-Neto, J. C., & Caperuto, E. C. (2018). Beta-Alanine Supplementation Improved 10-km Running Time Trial in Physically Active Adults. Frontiers in physiology, 9, 1105. https://doi.org/10.3389/fphys.2018.01105