The blog that I wrote back in 2013 about using beetroot juice to boost endurance sports performance (read it here) is the most popular on my website by some distance, being accessed many times each week. At the time, the evidence seemed clear: taking 2 shots of beetroot concentrate prior to a race had been shown to significantly improve performance by boosting nitric oxide levels, leading in turn to more efficient oxygen use. Many of the studies at this point had been done with cyclists or runners, often using simulated time trials or measuring time to exhaustion in the lab. But the success of that early research has, of course, resulted in further studies that provide a more nuanced picture of the benefits of beetroot, and nitrate-containing vegetables generally.
So, it was great interest that I listened to Dr Lee Wylie from Exeter University, who has been heavily involved in nitrate studies since the early days, who gave an update on the latest research at the recent Innovations in Sports and Exercise Nutrition at the Royal Society of Medicine in London (7 March 2017). I’ve had a look at the papers he mentioned, together with others from the past 3-4 years, and it’s clear that while nitrate supplementation certainly has shown performance benefits, they won’t apply to all athletes or to all events. The amount of beetroot juice used and an individual’s training status are both very likely to be relevant. Below, I have put together a summary of key papers on nitrate over the past four years. Please use this to help inform you when making your decision about whether, how and when use beetroot juice as a potential performance aid for endurance sport.
1. Dose matters
A 2016 study by Wylie et al 1 found that supplementation with 6 mmol of dietary nitrate for 28 days reduced the steady state oxygen uptake by 3% during moderate intensity exercise in 34 healthy subjects, while a dose of 3 mmol had no effect.
This backed up the findings from a 2013 study 2 by the same authors, which showed no effect from 4.2 mmol of nitrate, a 1.7% reduction in oxygen uptake with 8.4 mmol of nitrate and a 3% reduction with 16.8 mmol. Interestingly, there was no difference in time to failure between the 8.4 mmol dose and the 16.8 mmol dose.
Note: 8 mmol of nitrate is found in two x 70cl bottles of Beet IT Sport Shots – you can buy this here – UK only.
2. The benefits of taking beetroot juice are maintained for at least two days after stopping chronic supplementation.
The same 2016 study 1 showed that the positive effects seen from 28 days of supplementation with 6 mmol of dietary nitrate were maintained during a further test on day 30, despite the dose that day being a placebo and levels of nitrite in the blood having returned to normal.
3. Taking beetroot juice appears to be more effective over shorter distances
Shannon et al (2017) 3 gave 8 trained runners and triathletes either two 70cl shots of beetroot juice or a placebo three hours before different length runs on a treadmill. There was a significant improvement in those taking the beetroot over 1500m but no difference in performance over 10km.
4. The shorter the interval, the more effective the beetroot juice
Wylie et al 4 found in 2016 that supplementing beetroot juice improved performance in 6 second cycling sprints compared with placebo, but not in longer 30 second or 60 second sprints. Participants took beetroot juice or placebo for 5 days, with tests on days 3, 4 and 5 in this crossover study.
5. Beetroot juice may augment training adaptations from sprint interval training
The same group found in a 2017 study 5 that, compared with placebo, not only did beetroot juice reduce the oxygen cost of exercise during 4 weeks of sprint interval training by 36 recreationally active subjects, but it was also shown to have enhanced some metabolic adaptations to training in the muscle.
6. Beetroot juice may have a preferential effect on Type II muscle fibres
Jones et al 6 found in 2016 that increased blood flow resulting from nitrate supplementation may not reach the Type I muscle fibres predominant in endurance athletes. This helps to explain the likely greater benefits in sprinting and intermittent exercise like team sports, where Type II muscle fibres dominate, which the research is now indicating 7.
7. Results of using beetroot juice while running at altitude are conflicting
Arnold et al 8 had 10 well-trained male runners take 7 mmol of dietary nitrate or placebo 2.5 hours before (1) exercising to exhaustion at a simulated altitude of 4000m (2) running a 10km time trial at a lower simulated altitude of 2500m. No difference in performance was seen between nitrate supplementation and placebo.
Conversely, in a study by Shannon et al 9, where 12 healthy males of varying fitness levels consumed c 15 mmol of dietary nitrate or placebo three hours before performing a warm up followed by a 1500m time trial at a simulated altitude of 2500m, nitrate was shown to improve performance in all participants by an average of 3.2%, with no apparent relationship to fitness levels.
Note the different doses in these two studies: 7 mmol and 15 mmol.
8. A diet high in nitrate-rich vegetables provides similar benefits to nitrate supplementation
Porcelli et al 10 undertook a crossover study with 7 subjects who consumed a diet with a ‘normal’ nitrate content for 6 days (resulting in blood plasma levels of 2.9 mmol), then a diet with ‘high’ nitrate content for 6 days (resulting in blood plasma levels of 8.2 mmol), with a 20 day washout period in between. An average 7.2% reduction in oxygen cost was seen across three different types of exercise: sprint ability, knee extensions and moderate intensity cycling. The biggest improvement came from the cycling test with a 10% reduction. This suggests following a high nitrate diet during heavy training blocks may be beneficial. Sources other than beetroot include rocket, kale, spinach, collard greens and Chinese cabbage.
9. Dietary nitrate appears to have less of a performance impact in highly trained aerobic athletes
A 2015 study, also by Porcelli et al 11, took 21 subjects with varying aerobic fitness levels (VO2 max ranged from 28.2 to 81.7 mL/kg/min) and gave them 5.5 mmol nitrate or placebo for 6 days before performing a number of running tests. These were then repeated after a crossover period. The less aerobically fit the subject, the greater their improvement in a 3km time trial when supplementing nitrate versus placebo. The more highly trained subjects also saw a lower rise in blood nitrate levels when supplementing nitrate. The authors concluded that the optimal nitrate loading regime would depend on an athlete’s fitness level.
Lastly, a tip from Dr Wylie: never use anti-bacterial mouthwash before drinking beetroot juice! This is because you need bacteria on your tongue to convert the nitrate to the nitrite form that can be used in the body.
Jo Scott-Dalgleish BSc (Hons) is a BANT Registered Nutritionist, writing and giving talks about nutrition for endurance sport. Based in London, she also works as a Registered Nutritional Therapist, conducting one–to–one consultations with triathletes, distance runners and cyclists to help them eat well, be healthy and perform better through the creation of an individual nutritional plan. To learn more about these consultations, please visit www.nutritionforendurancesports.co.uk
1 Wylie et al. Dose-dependent effects of dietary nitrate on the oxygen cost of moderate-intensity exercise: Acute vs. chronic supplementation. Nitric Oxide. 2016.Jul 1; 57:30-9 https://www.ncbi.nlm.nih.gov/pubmed/27093910
2 Wylie et al. Beetroot juice and exercise: pharmacodynamic and dose-response relationships. J Appl Physiol (1985). 2013 Aug 1;115(3):325-36 https://www.ncbi.nlm.nih.gov/pubmed/23640589
3 Shannon et al. Dietary nitrate supplementation enhances short but not longer duration running time-trial performance. Eur J Appl Phyiol. 2017. Apr;117(4): 775-785 https://www.ncbi.nlm.nih.gov/pubmed/28251402
4 Wylie et al. Influence of beetroot juice supplementation on intermittent exercise performance. Eur J Appl Physiol. 2016. Feb; 116(2):415-25 https://www.ncbi.nlm.nih.gov/pubmed/26614506
5 Thompson et al. Influence of dietary nitrate supplementation on physiological and muscle metabolic adaptations to sprint interval training. J Appl Physiol (1985). 2017 Mar 1:122(3):642-652 https://www.ncbi.nlm.nih.gov/pubmed/27909231
6 Jones et al. Fibre Type-Specific Effects of Dietary Nitrate. Exerc Sport Sci Rev. 2016. Apr; 44(2): 53-60 https://www.ncbi.nlm.nih.gov/pubmed/26829247
7 Wylie et al. Dietary nitrate supplementation improves team sport-specific intense intermittent exercise performance. Eur J Appl Physiol. 2013. Jul; 11397): 1673-84 https://www.ncbi.nlm.nih.gov/pubmed/23370859
8 Arnold et al. Beetroot juice does not enhance altitude running performance in well trained athletes. Appl Physiol Nutr Metab. 2015 Jun;40 (6):590-5 https://www.ncbi.nlm.nih.gov/pubmed/25942474
9 Shannon et al. Dietary nitrate supplementation enhances high-intensity running performance in moderate normobaric hypoxia, independent of aerobic fitness. Nitric Oxide. 2016 Sep 30; 58:63-70 https://www.ncbi.nlm.nih.gov/pubmed/27553127
10 Porcelli et al. Effects of a short-term high-nitrate diet on exercise performance. Nutrients. 2016 Aug 31; 8(9) https://www.ncbi.nlm.nih.gov/pubmed/27589795
11 Porcelli et al. Aerobic fitness affects the exercise performance responses to nitrate supplementation. Med Sci Sports Exerc. 2015 Aug; 47(8):1643-51 https://www.ncbi.nlm.nih.gov/pubmed/25412295