Supplement Review: inorganic nitrates reduce blood pressure and increase exercise capacity

by Brett Holland, PT, DPT, CSCS

If you are not aware of the amazing health benefits of nitrates, then take a minute and appreciate the recent scientific data published on inorganic nitrates.  First and foremost, inorganic nitrates are more commonly known as nitric oxide boosters (NO).  They are present in many different types of vegetables such as spinach and beets.  Most of the research published on inorganic nitrates has used beets or beetroot juice as the source.  After ingesting the source of inorganic nitrate, it is digested and ends up in your saliva, where the bacteria convert the inactive form (nitrate) to the active form (nitrite).  Once converted to the active form, it has a host of health benefits.  Here are some of the amazing benefits of inorganic nitrates:

Effects on Cardiovascular Disease

• Approximately 40% of all deaths can be attributed to cardiovascular disease [1].
• A 2013 systematic review with meta-analysis (high level of evidence) found an average reduction in systolic blood pressure (top number)  of 4.4 mm HG and a smaller reduction in diastolic pressure of 1.1 mm HG with inorganic nitrate ingestion [2].
• The same study found the greater the dose of nitrate, the greater the reduction in systolic blood pressure [2].
• It appears at this time that nitrates have a greater effect on systolic blood pressure than diastolic blood pressure.
• Reducing systolic blood pressure by 5 mm HG may reduce the risk of mortality due to stroke by 14% and from cardiovascular disease by 9% [2]!

Effects on Peripheral Arterial Disease (PAD is a circulation problem, typically in the lower extremities resulting in severe burning and pain in the calves with walking)

• A 2011 study found 500 ml of beetroot juice increased walking time prior to the onset of claudication by 18% [3].
• In a 2014 literature review Clements et al. concluded, “As such, individuals suffering from hypertension, peripheral artery disease and ischemia-related diseases (e.g., blood flow disorders) may be relieved by regular consumption of nitrate-rich vegetables—or perhaps using beetroot juice as a source for enhancing blood flow both at rest and during exercise. Individuals seeking said benefits should note that ingestion of 500 mL (~2 cups) of BRJ provides sufficient NO₃⁻ (~5–9 mmol) content to provide ergogenic and health benefit”[1].

Effects on Exercise

• A 2013 systematic review found a significant moderate benefit of nitrate supplementation on time to exhaustion [4].
• The same review found a small positive effect on exercise performance [4].
• Beetroot juice was found to improve 10 km timed trial and power output in trained cyclists [5].
• A 2013 study found beetroot juice beneficial during intermittent exercise and may be beneficial during team sports [6].
• In swimmers beetroot juice increased workload at the anaerobic threshold and aerobic energy cost was significantly reduced [7].

Toxicity:

• Originally nitrates were believed to be harmful to ingest and potentially carcinogenic.
• The previously mentioned 2014 literature review states, ” current critical reviews of NO₃⁻ in animal toxicology literature indicate no evidence for carcinogenesis or mutagenesis [16,61] “[1].
• In addition the authors concluded, “It is evident that longstanding concerns about the toxicity of orally consumed NO₃⁻ and NO₂⁻ (specifically those from natural vegetable sources) have been overstated [16].”[1].
• In addition a 2014 review concluded, “The expert consensus view is that nitrate supplementation with vegetable products such as beetroot juice is very unlikely to be harmful [78, 79]. “[8].

Summarizing the main benefits of inorganic nitrates:

Nitrate supplementation may:

• allow you exercise longer
•  provide a slight performance boost in time trials and team sport performance
• reduce systolic blood pressure
• improve exercise capacity in individuals with blood flow disorders

Dosing inorganic nitrates:

• Nitrates appear to peak about 2-3 hours after ingestion.  Therefore this would be the ideal time to ingest them (for exercise).
• The typical studied dose is 500 ml of beetroot juice, which equates to roughly 2 cups.
• There are a variety of nitrate supplements on the market, for now it is generally recommended to acquire nitrates either via a high vegetable diet or beetroot juice as these are the most studied and generally safe.   They also have additional vitamins (C in particular) and antioxidants which are believed to prevent carcinogenic activity.  Supplements may not provide this additional protection.

References

1.  Clements, William, Sang-Rok Lee, and Richard Bloomer. “Nitrate Ingestion: A Review of the Health and Physical Performance Effects.” Nutrients 6.11 (2014): 5224-264. PubMed
2. Siervo, M., J. Lara, I. Ogbonmwan, and J. C. Mathers. “Inorganic Nitrate and Beetroot Juice Supplementation Reduces Blood Pressure in Adults: A Systematic Review and Meta-Analysis.” Journal of Nutrition 143.6 (2013): 818-26. Pubmed.
3. Kenjale, A. A., K. L. Ham, T. Stabler, J. L. Robbins, J. L. Johnson, M. Vanbruggen, G. Privette, E. Yim, W. E. Kraus, and J. D. Allen. “Dietary Nitrate Supplementation Enhances Exercise Performance in Peripheral Arterial Disease.” Journal of Applied Physiology 110.6 (2011): 1582-591. PubMed.
4. Hoon, MW, NA Johnson, PG Chapman, and LM Burke. “The Effect of Nitrate Supplementation on Exercise Performance in Healthy Individuals: A Systematic Review and Meta-analysis.” Int J Sport Nutr Exerc Metab. (2013):  PubMed.
5. Cermak, NM, MJ Gibala, and LJ Van Loon. “Nitrate Supplementation’s Improvement of 10-km Time-trial Performance in Trained Cyclists.” Int J Sport Nutr Exerc Metab. (2012):  PubMed
6. Wylie, Lee J., Magni Mohr, Peter Krustrup, Sarah R. Jackman, Georgios Ermιdis, James Kelly, Matthew I. Black, Stephen J. Bailey, Anni Vanhatalo, and Andrew M. Jones. “Dietary Nitrate Supplementation Improves Team Sport-specific Intense Intermittent Exercise Performance.” European Journal of Applied Physiology Eur J Appl Physiol 113.7 (2013): 1673-684. Pubmed.
7. Pinna, Marco, Silvana Roberto, Raffaele Milia, Elisabetta Marongiu, Sergio Olla, Andrea Loi, Gian Migliaccio, Johnny Padulo, Carmine Orlandi, Filippo Tocco, Alberto Concu, and Antonio Crisafulli. “Effect of Beetroot Juice Supplementation on Aerobic Response during Swimming.” Nutrients 6.2 (2014): 605-15. Pubmed.
8. Jones, Andrew M. “Dietary Nitrate Supplementation and Exercise Performance.” Sports Med Sports Medicine 44.S1 (2014): 35-45. PubMed.