Updated: Aug 5, 2018
In part 1 of this series, it was shown that nitrate supplementation enhances performance and identified the vegetables which contain the most nitrate. Questions to be answered in this part…
When should nitrates be consumed?
Does is work for endurance events or sprint events?
Training or racing?
Age group or elite athletes?
Have swimmers specifically been tested?
First, some feedback received -
What is the difference between nitrates/nitrites in vegetables and nitrates/nitrites in meat?
The difference lies in the formation of different compounds from nitrates that either benefit or harm us. There are 35+ naturally occurring compounds in plants – including vitamin C, vitamin E, and caffeic acid – that block formation of nitrosamines (1). Nitrosamine from nitrates/nitrites in meat has been shown to elevate risk of esophageal, bladder, colon, prostate and thyroid cancers (1,5). Meat contains no Vitamin C or caffeic acid and negligible amounts of E, or any of the 35+ phytonutrients in plants, and allows uninhibited formation of nitrosamines from nitrites. Processes within the body use the phytochemicals in fruits and vegetables to form beneficial nitric oxide.
Time of season to ingest nitrates –
As stated in part 1, nitrate supplementation induces angiogenesis and mitochondrial biogenesis (i.e. base training) and should therefore seriously be considered for ingestion at the commencement of the season when coaches and swimmers are looking to develop that aerobic base.
The level of athlete –
Nitrate supplementation efficacy has been studied extensively in recreational and sub-elite populations. In studies involving elite athletes, nitrate supplementation shows less promise, at least in endurance training. Top athletes have fewer ‘weak links in the chain’ that otherwise can be corrected with supplementation in sub-elite competitors. In other words, elite athlete physiology is maximized, and additional supplementation may not benefit much, or at all in endurance training. Indeed, the nitrate –> nitrite –> nitric oxide pathway is already boosted naturally from years of intense training (3). However, even in elite groups there are responders and non-responders. Jones (2014) found 20-25% of the elite population could improve by 0.5-1.5% in a time-trial with nitrate supplementation (2). At that level, that could be huge. Elite athletes need to consider experimenting to see if nitrate supplementation works.
What type of athlete –
Endurance athletes – In a meta-analysis of nitrate supplementation on endurance performance, McMahon et al. (2017) found “clear evidence” that dietary nitrate can boost aerobic exercise capacity as measured by time-to-exhaustion tests with less clear results in time-trial tests* (6). Time-to-exhaustion tests could mean more repeat intervals, improving training efficacy, and lending more evidence to supplement nitrate during training. Time-trial studies were not significant but did result in 0.8% improvement in times. Small, but meaningful improvements that are worth investigating.
Sprint athletes – The research examining the effects of nitrate on high intensity interval/sprint exercise is still in its infancy. What we do know is the pathway in which nitrate improves performance in endurance athletes is different than the pathway in which nitrate effects sprint athletes. As stated in part 1, nitrate improves endurance performance mainly by reducing the O2 cost of exercise. In sprint athletes, however, nitrate could improve performance by increasing contraction velocities in type II muscle fibers. Even more exciting, nitrate supplementation may work for all level of athletes including elite performers when doing high intensity interval training (7).
How much consumption –
There is a dose-response effect with nitrate supplementation, meaning, eat too little and there’s no effect; eat too much, and there’s no further benefit. 5-10mmol of nitrate, about 1-2 cups of beetroot juice, should benefit (3). If you’re a smaller athlete, a little less; if you’re a bigger athlete, a bit more than 2 cups juice. On average, vegetarian diets ingest about 4.3mmol of nitrate daily, so even vegetarians could benefit from nitrate supplementation (4). If you wish to eat your nitrate, you’ll have to eat a good-sized spinach/beet salad or about one large beet.
Testing swimmers specifically –
As expected, beetroot juice did reduce aerobic O2 cost and increased workload at anaerobic threshold in 30-something, moderately trained master’s swimmers (8). In another study, beetroot juice did not improve time-trial performance in moderately trained college swimmers (9). We saw that time-trial training may not be as responsive to nitrate as time-to-exhaustion training. Also, participants in this study took one dose of nitrate 3 hours before testing. Which brings us to…
Nitrate dosing –
Chronic dosing with nitrate seems to show more consistent results than single dosing before training lending weight to why the second swim study found no difference between supplementation and control. 7-15 days of dosing, 2-3 hours before training, seems to be most effective (6,7).
In part 3, we will cover the forms in which to eat/drink nitrate, so you don’t waste your money.
* Time-to-exhaustion tests are usually done by having participants go for as long as they can at a certain power output until failure. Time-trial tests attempt to cover a given distance in as short of time as possible.
Bartsch, Helmut, Hiroshi Ohshima, and Brigitte Pignatelli. "Inhibitors of endogenous nitrosation mechanisms and implications in human cancer prevention." Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 202.2 (1988): 307-324.
Jones, Andrew M. "Influence of dietary nitrate on the physiological determinants of exercise performance: a critical review." Applied Physiology, Nutrition, and Metabolism 39.9 (2014): 1019-1028.
Van De Walle, Gavin P., and Matthew D. Vukovich. "The Effect of Nitrate Supplementation on Exercise Tolerance and Performance: A Systematic Review and Meta-Analysis." The Journal of Strength & Conditioning Research 32.6 (2018): 1796-1808.
Lidder, Satnam, and Andrew J. Webb. "Vascular effects of dietary nitrate (as found in green leafy vegetables and beetroot) via the nitrate‐nitrite‐nitric oxide pathway." British journal of clinical pharmacology 75.3 (2013): 677-696.
Nitrate/Nitrite Toxicity: What Are the Health Effects from Exposure to Nitrates and Nitrites?. (2016). Retrieved July 10, 2018, from https://www.atsdr.cdc.gov/csem/csem.asp?csem=28&po=10.
McMahon, Nicholas F., Michael D. Leveritt, and Toby G. Pavey. "The effect of dietary nitrate supplementation on endurance exercise performance in healthy adults: a systematic review and meta-analysis." Sports medicine 47.4 (2017): 735-756.
Jonvik, K. L., et al. "Repeated-sprint performance and plasma responses following beetroot juice supplementation do not differ between recreational, competitive and elite sprint athletes." European journal of sport science 18.4 (2018): 524-533.
Pinna, Marco, et al. "Effect of beetroot juice supplementation on aerobic response during swimming." Nutrients 6.2 (2014): 605-615.
Lowings, Sam, et al. "Effect of dietary nitrate supplementation on swimming performance in trained swimmers." International journal of sport nutrition and exercise metabolism 27.4 (2017): 377-384.