Beetroot and beetroot juice are natural sources of dietary nitrates that may serve to enhance exercise performance. Leafy-green and root vegetables are a main source of dietary nitrates and provide high nitrate concentrations (McMahon 2017). Dietary nitrates play a role in vascular function and are thought to provide potential ergogenic effects. Beetroot has become popular in the realm of exercise performance due to its high concentration of nitrates. Beetroot supplementation could improve cardiorespiratory endurance and therefore improve athletic performance (Domínguez 2017). Beetroot juice may improve running performance, exercise time to exhaustion, and muscular efficiency during moderate intensity exercise (Ormsbee 2013).
When consumed, dietary nitrates are converted to nitric oxide (NO), which activates several mechanisms that influence skeletal muscle oxygen utilization (Domínguez 2017). "NO is a potent signaling molecule that plays a key role in vasodilation by relaxing smooth muscle and subsequently improving blood circulation" (McMahon 2017).
Due to its high nitrate concentration, beetroot juice increases nitric oxide (NO) levels, which in turn increases blood flow and gas exchange, strengthens muscle contraction, and increases mitochondrial biogenesis and efficiency. Supplementing nitrates increases the bioavailability of nitric oxide that subsequently influences muscle function to improve exercise performance, specifically aerobic metabolism. (Domínguez 2017)
Beetroot juice has shown to improve aerobic performance, power output, and resistance exercise performance by increasing time to fatigue and number of repetitions performed while also reducing the oxygen cost of exercise (Ormsbee 2013). Both acute and chronic supplementation with beetroot juice may improve cardiorespiratory performance at the anaerobic threshold and VO2max intensity (Domínguez 2017). While endurance exercise capacity is positively effected by dietary nitrate supplementation, there is less of an effect on time trial performance (McMahon 2017).
More research is needed to examine the optimal dosing strategies for ergogenic effect, but a dietary nitrate level of 1,500 mg/L appears effective for performance and health benefits without side effects (Ormsbee 2013). Beetroot juice should be consumed within 90 min before athletic activity, since peak nitrate value occurs within 2–3 hrs after ingestion (Domínguez 2017).
Overall, beetroot appears to have performance enhancing effects primarily for endurance exercise by reducing time to exhaustion and enhancing aerobic metabolism. There does not however, appear to be as significant of an effect on anaerobic performance. (Ormsbee 2013, Domínguez 2017, McMahon 2017)
Domínguez R, Cuenca E, Maté-Muñoz JL, García-Fernández P, Serra-Paya N, Estevan MCL, Herreros PV, Garnacho-Castaño MV (2017). Effects of beetroot juice supplementation on cardiorespiratory endurance in athletes. A systematic review. Nutrients, 9(1), 43.
McMahon NF, Leveritt MD, Pavey TG (2017). The effect of dietary nitrate supplementation on endurance exercise performance in healthy adults: A systematic review and meta-analysis. Sports Medicine, 47(4), 735-756.
Ormsbee M, Lox J, Arciero P (2013). Beetroot juice and exercise performance. Nutrition and Dietary Supplements, 5(default), 27-35.