Nutritional supplements – beetroot and caffeine

Save favourite 12 Mar March 2018

Nutritional supplements can give you that extra little advantage, which is crucial in a race. But they can't replace proper training, a well-balanced diet, adequate sleep or rest.

General background

Many athletes use nutritional supplements in an attempt to optimise performance and therefore gain an advantage in their sport. The use of nutritional supplements is of interest to both recreational and elite athletes aiming to improve performance. In certain competitive situations, improvements or decrements in performance by even very small margins could be meaningful in terms of a race outcome or result. In such cases, nutritional supplements could have a significant impact.

However, it is important that nutritional supplements are used responsibly, with reference to recommendations and with an awareness for the possibility of contamination (Maughan, 2005). Moreover, nutritional supplements should be used as just that, supplements, and not as an alternative to a well-balanced diet, sufficient sleep/recovery or appropriate training.

Beetroot juice

Beetroot juice is a supplement that has become popular in recent times, particularly among endurance athletes. Beetroot juice contains nitrate, which following ingestion is reduced to nitrite and subsequently nitric oxide. Nitrate is found naturally in foods, particularly vegetables such as beetroot, spinach and rocket (Jonvik et al., 2016). Nitric oxide is therefore produced in the body and has an important role in regulating blood flow, muscle contraction, glucose and calcium balance, aerobic energy delivery and respiration. The intake of beetroot juice, which increases the concentration of nitric oxide in the body, is thought to make these processes more efficient.

Previous studies have shown that beetroot juice supplementation improves the oxygen cost of exercise (i.e., work economy) by ~ 5% (Cermak et al., 2012). A more economical use of oxygen reduces the need for oxygen at a specific exercise intensity, or allows exercise at a higher intensity for the same oxygen uptake. Beetroot juice has also been shown to improve endurance performance in cycling by 1-6% (Cermak et al., 2012; Lansley et al., 2011) and high-intensity running by 1-4 % (Thompson et al., 2016).

Dosages and timing

An acute dose of 5–14 mmol of nitrate 2.5–3 h before competition has been shown to elicit performance-enhancing effects. This corresponds to one to two "Beet-It Sport Shot" bottles (70 mL). Well-trained athletes seem to need a higher intake (e.g., ~ 13 mmol, two 70 mL bottles) compared with untrained individuals. This may be due to athletes having higher baseline concentrations of nitrate in the body, as a result of a higher intake of nitrate-rich vegetables, as well as training effects.

Recent studies have shown chronic intakes of 5–8 mmol of nitrate over 3–15 days to elicit greater effects on performance than an acute does, although more research is needed in this area (McMahon et al., 2017). It is important not to ingest too high doses of nitrate, and not to drink beetroot juice every day. This may reduce the body's own natural production of nitrate. Instead, supplementation should be spared for specific training periods and competitions!

Side effects

Harmless red colouration of the urine is common following ingestion of beetroot juice or beetroots. Some people may feel nauseous or experience stomach cramps with beetroot juice supplementation. It is therefore important to test beetroot juice before using it prior to competition, to see how the body reacts.


Caffeine is commonly used by athletes due to its stimulating effect on the central nervous system, which thereby increases alertness and reduces the perception of effort. Some studies have also shown caffeine to have a stimulating effect on lipolysis, which increases fat oxidation and leads to reduced muscle glycogen depletion.

Previous research studies have shown that caffeine supplementation can improve endurance capacity by more than 20% (Pasman et al., 1995), as well as team-sport performance by up to 10 % (Stuart et al., 2005). Caffeine was removed from WADAs (World Anti-Doping Agency's) list of banned substances in the beginning of 2004.

Dosages and timing

Ingestion of 3–6 mg/kg body weight of caffeine 30–60 min prior to competition or training is the recommendation and has been shown to benefit performance (Goldstein et al., 2010). A higher intake of caffeine does not seem to provide any further benefit.

Side effects

Taking large amounts of caffeine may cause side effects such as stomach ache, nausea, vomiting, diarrhoea, palpitation, sleep discomfort and headache.

Combining beetroot juice and caffeine

Given the independent beneficial effects of beetroot juice and caffeine alone, and the different physiological pathways by which they appear to act, studies have been conducted to investigate whether the combination of these supplements has an additive effect on cycling and running performance (Glaister et al., 2015; Oskarsson & McGawley, 2018).

While results showed no performance-enhancing effects of combining the supplements, there were improvements in running economy and performance in certain individuals when ingesting beetroot juice and caffeine in combination with each other. It may therefore be worthwhile for individual athletes to test these nutritional aids in an attempt to improve performance by small margins, which in certain competitive situations could be meaningful. However, it should be noted that physiological and performance responses may also be worsened following supplementation with beetroot juice and/or caffeine, and in such situations ingestion of the supplements should be avoided.


Cermak, N. M., Gibala, M. J., & van Loon, L. J. C. 2012. Nitrate supplementation's improvement of 10-km time-trial performance in trained cyclists. Int. J. Sport Nutr. Exerc. Metab. 22: 64-71

Goldstein, E. R., Ziegenfuss, T., Kalman, D., Kreider, R., Campbell, B., Wilborn, C. Taylor, L., Willoughby, D., Stout, J., Graves, B. S., Wildman, R., Ivy, J. L., Spano, M., Smith, A. E., & Antonio, J. 2010. International society of sports nutrition position stand: caffeine and performance. J. Int. Soc. Sports Nutr. 7: 5

Glaister, M., Pattison, J. R., Muniz-Pumares, D., Patterson, S. D., & Foley, P. 2015. Effects of dietary nitrate, caffeine, and their combination on 20- km cycling time trial performance. J. Strength Cond. Res., 29, 165-174.

Jonvik, K. L., Nyakayiru, J., van Dijk, J-W., Wardenaar, F. C., van Loon., L. J. C., & Verdijk L. B. 2016. Habitual dietary nitrate in highly trained athletes. Int. J. Sport Nutr. Exerc. Metab. 27: 148-157

Lansley, K. E., Winyard, P. G., Bailey, S. J., Vanhatalo, A., Wilkerson, D. P., Blackwell, J. R., Gilchrist, M., Benjamin, N., & Jones, A. M. 2011. Acute dietary nitrate supplementation improves cycling time trial performance. Med. Sci. Sports Exerc. 43: 1125-1131

Maughan, R. J. 2005. Contamination of dietary supplements and positive drug tests in sport. J. Sports Sci. 23: 883-889

McMahon, N. F., Leveritt, M. D., & Pavey, T. G. 2017. The effect of dietary nitrate supplementation on endurance exercise performance in healthy adults: a systematic review and meta-analysis. Sports Med. 47: 735–756.

Oskarsson, J. & McGawley, K. 2018. No individual or combined effects of caffeine and beetroot-juice supplementation during submaximal or maximal running. Appl. Physiol., Nutr. and Metabol. doi: 10.1139/apnm-2017-0547

Pasman, W. J., Van Baak, M. A., Jeukendrup, A., & De Haan, A. 1995. The effect of varied dosages of caffeine on endurance performance time. Int. J. Sports Med. 16: 225-230

Stuart, G., Hopkins, W., Cook, C., & Cairns, S. 2005. Multiple effects of caffeine on simulated high-intensity team-sport performance. Med. Sci. Sports Exerc. 37: 1998-2004

Thompson, C., Vanhatalo, A., Jell, H., Fulford, J., Carter, J., Nyman, L., Bailey, S. J., & Jones A. M. (2016). Dietary nitrate supplementation improves sprint and high-intensity intermittent running performance. Nitric Oxide, 61: 55-61

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