Abstract
Consumption of beetroot juice (BRJ) supplements has become popular among athletes, because beets tend to be rich in nitrate (NO3-), which can enhance exercise performance by increasing nitric oxide production. The NO3- content of beets can vary significantly, however, making it difficult to know how much NO3- any product actually contains. Samples from 45 different lots of 24 different BRJ products from 21 different companies were therefore analyzed for NO3- (and nitrite; NO2-) concentration using high performance liquid chromatography. The NO3- and NO2- content, i.e., amount per serving, was then calculated based on either 1) the manufacturer's recommended serving size (for prepackaged/single dose products) or 2) as used in previous studies, a volume of 500 mL (for BRJ sold in bulk containers). There was moderate-to-large variability in NO3- content between samples of the same product, with a mean coefficient of variation of 30±26% (range 2 to 83%). There was even greater variability between products, with a ~50-fold range in NO3- content between the lowest and highest. Only five products consistently provided ≥5 mmol of NO3- per serving, which seems to be the minimal dose required to enhance exercise performance in most individuals. NO2- contents were generally low (i.e., ≤0.5% compared to NO3-), although two products contained 10 and 14%. The present results may be useful to athletes and their support staff contemplating which (if any) BRJ product to utilize. These data may also offer insight into variability in the literature with respect to the effects of BRJ on exercise performance.
Highlights
Numerous studies in recent years have investigated the effects of dietary nitrate (NO3−) on the physiological responses to, and/or performance during, exercise
Based on studies demonstrating that beetroot juice (BRJ) ingestion can enhance exercise performance (Jones et al, 2018), a large number of BRJbased supplements are marketed to athletes
Athletes and/or their support staff must generally rely on claims made by producers to determine whether such supplements contain To hsueflpficfiiellntthNisOk3n−otwoleimdgpeacgtapp,hywseiomloegaiscuarlefdunthcetioNnO. 3−
Summary
Numerous studies in recent years have investigated the effects of dietary nitrate (NO3−) on the physiological responses to, and/or performance during, exercise. This interest stems from the fact that dietary NO3− is an important source of nitric oxide (NO) via the “reverse” NO3− → nitrite (NO2−) → NO enterosalivary pathway (Kharti et al, 2017). Most studies of dietary NO3− and exercise have used beetroot juice (BRJ) as a source. This is because beets are relatively rich in. Content of the BRJ supplement used and/or measured any biomarkers of NO to ensure bioavailability
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