Nitrate supplementation boosts muscle power Original paper

This meta-analysis of 19 crossover randomized controlled trials found that acute nitrate supplementation improved muscle power by about 5%.

This Study Summary was published on December 2, 2021.

Background

Over 100 studies have investigated the effects of dietary nitrates (commonly in the form of beetroot juice) on physiological responses and physical performance during endurance activities, and a consistent improvement in time-to-exhaustion tasks has been reported.[1][2] More recently, the attention of the scientific community has shifted to the effects of nitrate supplementation on physical performance during brief anaerobic activities (e.g., strength- or sprint-based exercise).

Whereas muscle strength represents the capacity to produce force, muscle power is the product of the force and velocity of muscle contraction. Power is likely more important than strength in determining sports performance and the ability to perform activities of daily living (e.g., climbing stairs).[3][4] Despite an increasing amount of research on the effect of nitrate supplementation on muscle power, there had yet to be a quantitative assessment of the available evidence — which the present study provided.

The study

This meta-analysis of 19 crossover randomized controlled trials examined the effects of nitrate supplementation on muscle power in 268 participants (218 men, 50 women). Muscle power was assessed via isokinetic dynamometry, cycle ergometry, or the inertial-load method. In most of the trials, the participants took an acute dose (14/19 studies) of beetroot juice (17/19 studies) containing an estimated 6.4–15.9 mmol (397–986 mg) of nitrates.

The results

Nitrate supplementation was found to have a small-to-medium effect on muscle power (standardized mean difference: 0.45). The subgroup analyses revealed that a single dose of nitrate was more effective than a multi-day dosing regimen. Also, sex, age, and the amount of muscle mass involved in the exercise test (e.g., knee extension vs. cycling) did not influence the effect of nitrate.

Note

A limitation of this meta-analysis is that most of the included studies assessed neither the actual dose of nitrates ingested nor the plasma levels of nitrates and/or nitrites following ingestion. This is doubly problematic, because the nitrate content of beetroot juice can vary considerably, even when samples are obtained from the same manufacturer,[5] and so plasma levels following ingestion likely vary considerably too.

The big picture

Nitrates can be found in different foods, notably beetroot and leafy green vegetables. The following table uses averages from multiple samples. Farming techniques, transport, storage conditions, and cooking methods can all greatly affect the actual nitrate and oxalate content of your food.

Nitrate-rich vegetables (mg per 100 g)

NITRATE-RICH VEGETABLESNitrates (mg)Total oxalate (mg)Soluble oxalate (mg)Vitamin K~1~ (mcg)
Arugula/rocket362.47.1<0.5108.6
Turnip greens346.750251
Dill259159600
Collard greens254.5450437.1
Spinach248.5656542.6482.9
Swiss chard236.3964207.7830
Turnips217.42100.1
Rhubarb199.980522329.3
Beetroot199.212174.90.2
Celery196.417.5<0.529.3
Mustard greens187.5128.7257.5
Radish177.39.2<0.51.3
Lettuce168.913.6<0.5126.3
Watercress16410<0.5250
Bok choy162245.5
Kale137.520704.8
Parsley130.47136761,640

References: Jackson et al. Nutr Res Rev. 2017[6] ● Lidder and Webb. Br J Clin Pharmacol. 2013[7] ● Griesenbeck et al. Nutr J. 2009[8] ● Tamme et al. Food Addit Contam. 2006[9] ● Siener et al. Food Chem. 2006[10] ● Hönow and Hesse. Food Chem. 2002[11] ● Santamaria et al. J. Sci. Food Agric. 1999[12]Dr. Duke's Phytochemical and Ethnobotanical databasesFoodData Central

Nitrates break down into nitrites, which circulate in the body and are turned into nitric oxide (NO). NO promotes vasodilation and improves blood flow to skeletal muscles.

How nitrates are converted into nitric oxide

image

A robust body of evidence demonstrates a clear ergogenic effect of nitrate supplementation in recreationally active, young, healthy men across various forms of exercise.[13] However, nitrate supplementation is clearly more beneficial for certain types of exercise than for others, and the effect size reported in the present study (i.e., 0.45) is substantially larger than what’s been reported for other measures of physical performance. This includes muscular strength (0.08), time-trial performance (0.086), muscular endurance (0.31),[14] and performance during time-to-exhaustion tasks (0.32).[13][14]

It’s also becoming increasingly apparent that training status mediates the effects of nitrate supplementation. Nitrates are best known for improving performance during time-to-exhaustion tasks, but this ability is negated in athletes with a VO2max above 64.9 mL/kg/min.[13] Unfortunately, the present meta-analysis did not assess the influence of training status on the effect of nitrate supplementation on muscle power; it only noted that 2 of the 3 trials with the smallest effect size included highly trained sprinters.

Nitrates exert their ergogenic effects via a couple of mechanisms:

  • They improve the efficiency of skeletal-muscle contraction by reducing the oxygen cost of exercise. The muscles can therefore perform more work per unit of time for the same energy cost.[15]
  • They improve the contractile properties of muscles by increasing intracellular concentrations of calcium (which triggers muscular contractions) and the muscle fibers’ sensitivity to calcium.[16]

Potential mechanisms for the effects of NO on exercise

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This Study Summary was published on December 2, 2021.

References

  1. ^Helton O Campos, Lucas R Drummond, Quezia T Rodrigues, Frederico S M Machado, Washington Pires, Samuel P Wanner, Cândido C CoimbraNitrate supplementation improves physical performance specifically in non-athletes during prolonged open-ended tests: a systematic review and meta-analysisBr J Nutr.(2018 Mar)
  2. ^Gavin P Van De Walle, Matthew D VukovichThe Effect of Nitrate Supplementation on Exercise Tolerance and Performance: A Systematic Review and Meta-AnalysisJ Strength Cond Res.(2018 Jun)
  3. ^Kieran F Reid, Roger A FieldingSkeletal muscle power: a critical determinant of physical functioning in older adultsExerc Sport Sci Rev.(2012 Jan)
  4. ^D BakerComparison of upper-body strength and power between professional and college-aged rugby league playersJ Strength Cond Res.(2001 Feb)
  5. ^Edgar J Gallardo, Andrew R CogganWhat's in Your Beet Juice? Nitrate and Nitrite Content of Beet Juice Products Marketed to AthletesInt J Sport Nutr Exerc Metab.(2019 Jul 1)
  6. ^Jackson J, Patterson AJ, MacDonald-Wicks L, McEvoy MThe role of inorganic nitrate and nitrite in CVDNutr Res Rev.(2017 Dec)
  7. ^Lidder S, Webb AJVascular effects of dietary nitrate (as found in green leafy vegetables and beetroot) via the nitrate-nitrite-nitric oxide pathwayBr J Clin Pharmacol.(2013 Mar)
  8. ^Griesenbeck JS, Steck MD, Huber JC Jr, Sharkey JR, Rene AA, Brender JDDevelopment of estimates of dietary nitrates, nitrites, and nitrosamines for use with the Short Willet Food Frequency QuestionnaireNutr J.(2009 Apr 6)
  9. ^Tamme T, Reinik M, Roasto M, Juhkam K, Tenno T, Kiis ANitrates and nitrites in vegetables and vegetable-based products and their intakes by the Estonian populationFood Addit Contam.(2006 Apr)
  10. ^Siener et alOxalate contents of species of the Polygonaceae, Amaranthaceae and Chenopodiaceae familiesFood Chemistry.(2006 Dec)
  11. ^Hönow R, Hesse AComparison of extraction methods for the determination of soluble and total oxalate in foods by HPLC-enzyme-reactorFood Chemistry.(2002 SEPT)
  12. ^Santamaria P, Elia A, Serio F, Todaro EA survey of nitrate and oxalate content in fresh vegetablesJ. Sci. Food Agric..(1999 SEPT)
  13. ^Jonathon W Senefeld, Chad C Wiggins, Riley J Regimbal, Paolo B Dominelli, Sarah E Baker, Michael J JoynerErgogenic Effect of Nitrate Supplementation: A Systematic Review and Meta-analysisMed Sci Sports Exerc.(2020 Oct)
  14. ^Thiago Silveira Alvares, Gustavo Vieira de Oliveira, Mônica Volino-Souza, Carlos Adam Conte-Junior, Juan Manuel MuriasEffect of dietary nitrate ingestion on muscular performance: a systematic review and meta-analysis of randomized controlled trialsCrit Rev Food Sci Nutr.(2021 Feb 8)
  15. ^Andrew M Jones, Christopher Thompson, Lee J Wylie, Anni VanhataloDietary Nitrate and Physical PerformanceAnnu Rev Nutr.(2018 Aug 21)
  16. ^Andrew R Coggan, Linda R PetersonDietary Nitrate Enhances the Contractile Properties of Human Skeletal MuscleExerc Sport Sci Rev.(2018 Oct)