The effects of dietary nitrate supplementation on endurance exercise performance and cardiorespiratory measures in healthy adults: a systematic review and meta-analysis.

Chloe Gao, Saurabh Gupta, Taranah Adli, Winston Hou, Reid Coolsaet, Abigail Hayes, Kevin Kim, Arjun Pandey, Jacob Gordon, Gurneet Chahil, Emilie P Belley-Cote, Richard P Whitlock

Journal: Journal of the International Society of Sports Nutrition 2021;18(1):55

PMID: 34243756

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Plain Language Summary

The ability to increase endurance to improve their physical fitness is of great interest to athletes. Several dietary components have been shown to increase endurance especially those which contain nitrates. It is thought that nitrates, which are found in beetroots, pomegranates, green leafy vegetables, collard greens, lettuce and spinach, aid endurance through their action on improving blood flow to the muscles, helping to improve contraction of the muscles, through increased energy production, through improved oxygen flow and through sugar and nutrient balance. However, studies in humans on the effects of nitrates on exercise endurance have been conflicting. This systematic review and meta-analysis aimed to summarise the research on the use of nitrates during exercise. The results showed that nitrate supplementation improved muscle power, time to exhaustion and distance travelled, although no difference was found to perceived exertion, time trial performance and work done. It was concluded that nitrate supplementation is of benefit to improve exercise endurance, based on very low to moderate quality evidence. This study could be used by health care professionals to recommend a nitrate rich diet and possibly a nitrate supplement to improve exercise performance.

Abstract

BACKGROUND

Nitrate supplementation is thought to improve performance in endurance sports.

OBJECTIVE

To meta-analyze studies evaluating the effect of nitrate supplementation on endurance sports performance among adults.

DATA SOURCES

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Web of Science and CINAHL without language restrictions.

METHODS

We included studies that: 1) compared nitrate supplementation with placebo; 2) enrolled adults engaging in an endurance-based activity; and 3) reported a performance measure or surrogate physiologic outcome. We evaluated risk of bias using the Cochrane Collaboration tool and pooled data with a random-effects model. We used the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach to evaluate confidence in estimates.

RESULTS

We included 73 studies (n = 1061). Nitrate supplementation improved power output (MD 4.6 watts, P < 0.0001), time to exhaustion (MD 25.3 s, P < 0.00001), and distance travelled (MD 163.7 m, P = 0.03). We found no significant difference on perceived exertion, time trial performance and work done. Nitrate supplementation decreased VO (MD - 0.04 L/min, P < 0.00001) but had no significant effect on VO or blood lactate levels.

CONCLUSION

The available evidence suggests that dietary nitrate supplementation benefits performance-related outcomes for endurance sports.

Address: Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.; Department of Surgery, McMaster University, Hamilton, Ontario, Canada.; Faculty of Biomedical Sciences, University of Western Ontario, London, Ontario, Canada.; Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada.; University of Guelph, Guelph, Ontario, Canada.; Queen's University, Kingston, Ontario, Canada.; Michael G. DeGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada.; Department of Health Research Methods, Evidence and Impact, McMaster University, Hamilton, Ontario, Canada.; Population Health Research Institute, Hamilton, Ontario, Canada.; Saint James School of Medicine, Park Ridge, USA.; Department of Medicine, McMaster University, Hamilton, Ontario, Canada.; Department of Surgery, McMaster University, Hamilton, Ontario, Canada. [email protected].; Department of Health Research Methods, Evidence and Impact, McMaster University, Hamilton, Ontario, Canada. [email protected].; Population Health Research Institute, Hamilton, Ontario, Canada. [email protected].; David Braley Cardiac, Vascular and Stroke Research Institute, 237 Barton St. E., Hamilton, Ontario, L8L 2X2, Canada. [email protected].

DOI: 10.1186/s12970-021-00450-4

Patient Centred Factor

Triggers: Endurance exercise

Clinical Imbalances

Structural Integrity and Musculoskeletal

Modifiable Lifestyle Factors

Diet Exercise and movement

Nutrition Evidence Keywords

Exhaustion Exertion Nitrate supplementation

Bioactive Substances

Nitrates

Link outs

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Medical:

https://medlineplus.gov/dietarysupplements.html

MeSH Terms: Adult, Athletes, Athletic Performance, Bias, Cardiorespiratory Fitness, Dietary Supplements, Exercise Tolerance, Humans, Lactic Acid, Nitrates, Oxygen Consumption, Physical Endurance, Publication Bias, Sedentary Behavior, Time Factors