Take Home Points on Nitrates and Sports Performance:
- Beetroot juice has potential for sports enhancement.
- Beetroot juice has minimal negative effect, as consuming more vegetables is a healthy ergogenic aide.
I hear a lot about drinking beet juice to help sports performance. Is there any science to
Yes. Beet juice contains relatively high levels of nitrate (NO3-), and nitrate from dietary sources is converted to nitrite (NO2-) by commensal bacteria in the mouth, and the nitrite is then absorbed in the blood stream. Nitrate reductase enzymes (which convert nitrate to nitrite) are found in certain bacteria in the mouth or intestines. Such bacterial nitrate reductases contribute significantly to a person’s endogenous nitrite pool.
Elevated nitrite levels improve may act to improve athletic performance through three different mechanisms, although the details are still being resolved.
1. Improved blood flow through vasodilation. Nitric oxide (NO) regulates arterial blood flow by causing smooth muscle cells which line the arteries to relax and open the vessel, allowing blood flow to increase. Nitric oxide was initially found to be produced by the conversion of L-arginine to L-citrulline by one of three enzymes, the nitric oxide synthases (NOS’s) including endothelial NOS (eNOS) neuronal NOS (nNOS) and inducible NOS (iNOS). However, these enzymes are oxygen dependent. For a long time after nitric oxide (NO) was discovered, scientists wondered how the body could rapidly deliver NO to locations with low oxygen where NO was needed.
Recently, nitrite itself has been shown to be a circulating storage pool for NO that the body can rapidly activate when needed. Rapid conversion of nitrite to NO can occur under ischemic conditions (low pH, low partial pressure of oxygen (pO2)). There are several enzymes which may act to reduce nitrite to NO, including deoxyhemoglobin, deoxymyoglobin, xanthine oxoreductase (XOR), neuroglobin, eNOS, and components of the mitochondrial electron transport chain. The different nitrite reductase “enzyme” systems operate along a range of physiological and pathological hypoxia, with hemoglobin reducing nitrite at an oxygen tension from 60 mm Hg down to 20 mm Hg, myoglobin active below 4 mm Hg, and xanthine oxoreductase and acidic reduction reducing nitrite at zero oxygen and low pH.
2. Reduced tissue oxygen demand through inhibition of mitochondrial respiration. NO reversibly inhibits mitochondrial respiration. Partial inhibition of mitochondrial respiration can regulate tissue oxygen gradients and conserve oxygen, particularly in conditions of physiological hypoxia (lack of oxygen). Inhibition of the most actively respiring mitochondria and those closest to the oxygen source would allow oxygen to diffuse beyond these mitochondria and further into the tissue to those sections of the tissue that are more distant from the oxygen source. This extension of the oxygen gradient deeper into the tissue would also extend the NO gradient in the tissue, thereby increasing the apparent bioavailability of both oxygen and NO.
3. Improvement in the efficiency of muscle contractility.
Some studies show that NO may improve muscle contractility, and therefore improve strength. It is hypothesized that increased levels of nitric oxide following supplementation may reduce the ATP cost of force production. Reduction of ATP use may be a consequence of nitric oxide’s regulatory effect on the ATP consuming processes of sarcoplasmic reticulum calcium pumping or myofibrillar actin-myosin interaction in force production. There is evidence that small increases in NO improves muscle metabolism, preventing excess calcium release and subsequently modulates the ATP cost of force production.
Do Nitrates it really help your performance?
Nitrate consumption has recently been referred to as “legal blood doping”. The effects are roughly similar to blood doping (red blood cell transfusion or erythropoietin (EPO) administration, which are of course illegal in sports) although most people show improved performance with blood doping, while not everyone gets a benefit from nitrates. Nitrate consumption shows a roughly 15% improvement in time to exhaustion, and a 2-3% improvement in overall performance. In one study of well-trained cyclists in a 50 mile time trial, athletes whose nitrite levels increased by about 100 nM over baseline showed a 2-3% improvement in overall performance. Nitrates have also been found to improve the efficiency (i.e., they can reduce the energy cost) of exercise as indicated by a 4%–5% reduction in oxygen uptake at steady state.
Nitrate consumption seems to help some people more than others. Some people may be “responders” and others “non-responders” to dietary NO3- supplementation. In addition, the duration and intensity of different types of exercise have not been thoroughly studied. In one study4, the number of non-responders (in terms of exercise capacity) decreased as the dose of nitrate ingested increased. Two of the subjects who did not respond at the lowest dose (4.2 mmol NO3-) did respond to the larger doses, and one subject who did not respond to low or medium doses of nitrate (4.2 or 8.4 mmol) did respond to the 16.8-mmol dose. This suggests that some individuals will require a larger acute dose than others to elicit any positive effects on exercise capacity from dietary NO3- ingestion.
In swimming, a recent study involving trained masters swimmers showed an increase in the workload at anaerobic threshold which was significantly increased by beet juice, and there was also a reduction in the aerobic energy cost of swimming at submaximal workload.
I really can’t stand beets, but I don’t want to mess around with supplements. Is there anything else I can eat or drink to get this benefit?
Yes! Spinach, celery, arugula, and other vegetables are relatively high in nitrates. Dark green leafy vegetable such as kale and chard are also good candidates. Interestingly, the nitrate levels in hot dogs are actually much lower than what is found in vegetables. Nitrate supplements are also widely available.
How much beet juice should I drink? When should I drink it?
Studies have shown that plasma nitrite levels are maximal at about 2-3 hours after ingesting bee
Nitrite levels appear to be elevated for up to 8 to 12 hours after nitrate consumption in the absence of exercise. However, this depends on the amount consumed, and is likely to be dependent on the duration and intensity of exercise.
A few caveats: Be sure not to take nitrite as a supplement – too much of that can be potentially lethal! Also, don’t use nitrates if you are taking Viagra or similar medications as the combination can cause a severe drop in blood pressure. If you are unsure, be sure to consult your doctor or pharmacist. Don’t use antiseptic mouth wash while you are consuming nitrates, as that can kill the bacteria that convert nitrates to nitrites.
Bottom line: You may want to try consuming different amounts of nitrates at different times. If you compete in endurance events such as marathons or open-water swimming events where you are allowed to consume drinks part way through, you might want to drink some beet juice then. After all, would it kill you to eat your vegetables?
- Webb AJ, Patel N, Loukogeorgakis S, Okorie M, Aboud Z, et al. (2008) Acute Blood Pressure Lowering, Vasoprotective, and Antiplatelet Properties of Dietary Nitrate via Bioconversion to Nitrite. Hypertension 51: 784-790.
- Cosby K, Partovi K, Crawford J, Patel R, Reiter C, et al. (2003) Nitrite reduction to nitric oxide by deoxyhemoglobin vasodilates the human circulation. Nature Medicine 9: 1498-1505.
- Gladwin MT, Schechter AN (2004) NO Contest: Nitrite Versus S-Nitroso-Hemoglobin. Circ Res 94: 851-855.
- Tiso M, Tejero J, Basu S, Azarov I, Wang X, et al. (2011) Human Neuroglobin Functions as a Redox-regulated Nitrite Reductase. J Biol Chem 286: 18277-18289.
- Shiva S, Sack MN, Greer JJ, Duranski M, Ringwood LA, Burwell, et al. (2007) Nitrite augments tolerance to ischemia/reperfusion injury via the modulation of mitochondrial electron transfer. J Exp Med 204: 2089-2102.
- Loke KE, Laycock SK, Mital S, Wolin MS, Bernstein R, et al. (1999) Nitric Oxide Modulates Mitochondrial Respiration in Failing Human Heart. Circulation 100:1291-1297.
- Thomas DD, Liu X, Kantrow SP, Lancaster JRJ (2001) The biological lifetime of nitric oxide: Implications for the perivascular dynamics of NO and O2. PNAS 98: 355–360.
- Daryl P. Wilkerson et al., “Influence of acute dietary nitrate supplementation on 50 mile time trial performance in well-trained cyclists” Eur J Appl Physiol (2012) 112:4127–4134
- Marco Pinna et al., “Effect of Beetroot Juice Supplementation on Aerobic Responseduring Swimming”, Nutrients 2014, 6, 605-615; doi:10.3390/nu6020605
- Lee J. Wylie et al., “Beetroot juice and exercise: pharmacodynamic and dose-response Relationships” J Appl Physiol 115: 325–336, 2013
- Andrea Petróczi and Declan P Naughton, Potentially fatal new trend in performance enhancement: a cautionary note on nitrite, Journal of the International Society of Sports Nutrition 2010, 7:25
James Silver, PhD, is the Founder and President of Silver Medical, a first-to-market medical diagnostic company addressing the large unmet clinical need of real-time detection in sports-related concussion. The technology is based on changes in nitric oxide. He has 20 years of experience in medical device research and development in both small start-ups and large firms, taking products from concept through commercialization. He is the author or co-author on 16 scientific publications including as an invited author on nitric oxide as a diagnostic, and is a named inventor on 13 issued US patents including several related to nitrite measurement. He holds a Ph.D. in Chemical Engineering with specialization in vascular biology and polymer science.