Written By: Meg Mathias, Dietetic Intern, UTMB
Edited By: Brett Singer MS, RD, CSSD, LD with IRONMAN Sports Medicine Institute
Summary:
- Dietary nitrate can be found in leafy green vegetables as well as beets.
- Consuming foods rich in nitrate may improve blood pressure in adults.
- Consuming nitrate prior to high intensity exercise may improve performance.
While beets might not be a common first choice within the typical American diet, they have received a lot of recent attention due to their possible health benefits. Beets are a sweet root vegetable consisting of fiber, vitamins, and minerals and are notorious for their vibrant and eye-catching fuchsia exterior. Beets can be consumed in multiple forms, either as the raw vegetable or in powder form. When the powder is combined with water it creates a beetroot juice mixture.
Beets, also commonly referred to as beetroot, contain nitrates. Along with beets, dietary nitrate can be found in a variety of vegetables including many of the dark green leafy vegetables such as spinach, arugula and lettuce. When nitrates are consumed in the diet from foods such as leafy green vegetables, they are broken down by bacteria within the mouth into nitrite. This causes nitrite levels to increase within the blood.
Once an athlete begins exercising at a high intensity, nitrite then further converts to nitric oxide, a molecule which is helpful for health and performance. Nitric oxide is a molecule that has been observed to cause vasodilation. Vasodilation widens blood vessels leading to increased blood flow with fewer strictures in veins and other blood passages. When dietary nitrate is supplemented, nitric oxide concentrations are increased in the blood. There is a much greater amount of nitrates found in beetroot juice, usually around 400-500 milligrams, compared to concentrations of around 250 milligrams of inorganic nitrates naturally occurring in a half cup of raw beets (3).
How can beetroot juice and dietary nitrate help?
Beetroot juice has recently gained popularity as an ergogenic aid in athletes and the average adult population alike. When beetroot juice was supplemented in those performing high-intensity exercise, an overall reduction in oxygen consumption was observed. The reduction of oxygen cost can be attributed to several potential factors, including:
- Vasodilation providing improved blood flow to working muscle
- A reduction in energy required for muscle contraction
- The potential for more efficient energy production at a lower oxygen cost
Improved time to exhaustion, as well as improvements in time trial performance have been noted as a result of this improved oxygen economy (1). These results have not been consistent across all populations though, with some studies in elite athletes showing little to no benefit in comparison to supplementation in recreational athletes. In most cases, beetroot juice has improved performance in shorter duration high intensity exercise lasting less than 40 minutes.
The vessel expansion observed with nitric oxide also causes smooth muscles, such as cardiac muscles, to relax. This is a possible mechanism leading to a reduction in blood pressure, which is a positive indicator of overall cardiovascular health (4). Nitric oxide has also been theorized to increase cerebral blood flow, delaying the decline in cognitive function that is commonly associated with aging in older adult populations (4).
How does beetroot juice affect performance in resistance exercise?
A recent study by Mosher, et al. investigated the use of nitrate containing beetroot juice on the amount of bench press repetitions able to be completed at a set percentage of participant’s one rep maximum (2). Twelve young men consumed either 70 mL of beetroot juice (‘Beet It’) containing 400 mg of nitrate or a placebo. Beetroot juice was consumed daily during a 6- day period, with a 72-hour wash out period between trials.
Subjects who consumed beetroot juice completed a significantly greater amount of total repetitions. At the moment, studies looking at beetroot juice and resistance training are limited. More research is needed before a practical recommendation can be made.
Further investigation is warranted to study proper dosing and the effectiveness of beetroot juice on alternative populations, for example elite versus recreational athletes. Performing additional studies could further elucidate the relationship between nitric oxide and force generated by skeletal muscles. For now, it appears beetroot juice is a low risk and potentially beneficial supplement for improving blood pressure, and potentially short duration endurance exercise in recreational athletes.
Have questions? Please feel free to talk to an Athlete Training + Health Performance Coach or Brett Singer, Sports Dietitian MS, RD, CSSD, LD with the IRONMAN Sports Medicine Institute. Brett can be reached at brett.singer@memorialhermann.org or can be found on Twitter at @bsinger10.
References:
- Lansley, K. E., P. G. Winyard, J. Fulford, A. Vanhatalo, S. J. Bailey, J. R. Blackwell, F. J. DiMenna, M. Gilchrist, N. Benjamin, and A. M. Jones. 2011b. Dietary nitrate supplementation reduces the O2 cost of walking and running: a placebo-controlled study. J Appl Physiol 110(3):591-600. doi: 10.115201070
- Mosher SL, Sparks SA, Williams EL, Bentley DJ, McNaughton LR. Ingestion of a nitric oxide enhancing supplement improves resistance exercise performance. J Strength Cond Res. 2016;30:3520–4. doi: 10.1519/JSC.0000000000001437
- Santamaria P. Nitrate in vegetables: toxicity, content, intake, and EC regulation. J Sci Food Agric. 2006; 86:10 – 17. doi: 10.1002/jsfa.2351