Beetroot juice supplementation has been studied in different athletes and, for the most part, has been found to have positive effects on exercise performance, namely, improvement in oxygen consumption, time to exhaustion, or overall time to complete the exercise. Although studies presented here were well controlled, more research needs to be conducted in larger sample sizes, including women and different types of athletes to further evaluate its effects on performance.
WHAT IS BEETROOT?
The beet, or really, the “beetroot,” because it is the root of the plant that we eat, has been around for a long time. It is formally known as “Beta vulgaris” (10). Most of us would describe beetroots as deep red, almost purple in color; however, there are beetroots that are yellow and even red and white striped (11). Beetroot gets its color from betanin, which has been suggestive of preventing oxidative stress (10). The roots and leaves of the beetroot plant have been used to treat many illnesses, including constipation, wound healing, and even halitosis.
HOW CAN BEETROOT HELP ENDURANCE PERFORMANCE?
So, how might beetroot theoretically help endurance performance? Briefly, a compound called “nitric oxide” (often abbreviated NO) is a compound that is made in the body but also can be made from dietary nitrate (9). In the body, NO is synthesized by the action of the enzyme NO synthase on the circulating amino acid L-arginine (9). Nitrate is a natural substance in vegetables, especially in leafy green vegetables and in beetroots (6). After a vegetable like beetroot is consumed, some of that nitrate is then converted (chemically reduced) to nitrite by bacteria in the saliva, which is then converted to NO in the stomach because of the acidic environment in the stomach (3). Some of the nitrite will be absorbed through the small intestines and into the body and will be converted to NO that occurs in the blood and tissues (8). NO, in turn, might decrease the oxygen cost of a given intensity of exercise, leading to a greater amount of oxygen in the muscle and a lower rate of oxygen uptake in an endurance exercise (1,2).
RECENT RESEARCH ON BEETROOT AND EXERCISE PERFORMANCE
Lansley and colleagues (7) studied the effects of beetroot juice supplementation on the oxygen cost of walking and running in nine physically active men. This was a crossover randomized study, so each participant underwent each treatment, acting as his own control, and also strengthening this study because of its small sample size. They compared 0.5 L per day of beetroot juice with placebo (also 0.5 L per day) for 6 days each. Participants underwent treadmill exercise tests on days 4 and 5 of the supplementation/placebo period, and on day 6, they underwent a knee extension test.
Compared with placebo, beetroot supplementation significantly increased NO concentration in the blood and significantly decreased systolic blood pressure. Beetroot juice also showed significant improvements in the oxygen cost of walking and moderately intense running while increasing the time to exhaustion by 15% in severely intense running. Beetroot juice did not, however, improve mitochondrial oxidative capacity measured by knee extension using magnetic resonance spectroscopy.
More recently, Cermak et al. (5) evaluated the effects of beetroot juice supplementation in 12 male cyclists (mean age, 31 years; mean peak oxygen uptake, 58 mL/kg per minute; mean peak power output, 342 W). Similar to the study by Lansley et al. (7), this was a crossover study. Participants were to consume 140 L per day of beetroot juice or placebo (for this study, the researchers used a nitrate-depleted beetroot juice) for 6 days, with a 14-day washout period between trials. They reported a significantly improved time trial performance and power output and significantly lower submaximal oxygen consumption after the beetroot supplementation period. There were no differences between the beetroot juice and placebo in whole-body fuel selection and plasma lactate, glucose, and insulin concentrations.
In another 2012 publication, Masschelein et al. (9) examined the effect of beetroot juice on arterial, muscle, and cerebral oxygenation status, symptoms of acute mountain sickness, and exercise tolerance at a 5,000-m altitude in 15 young healthy male volunteers (mean age, 21 years; mean peak oxygen uptake, 61.7 mL/kg per minute). Beetroot was given at 0.07 mmol of nitrate per kilogram of body weight per day or the same amount as a control drink. Subjects had three sessions: one in a normal oxygen condition (just with the control drink) and the other two in a hypoxic condition using the control drink compared with the beetroot juice. Each drink was consumed for 6 days before testing. The authors found that short-term dietary beetroot supplementation improved arterial and muscle oxygenation status but did not improve cerebral oxygenation status during exercise in severe hypoxic conditions. This was an interesting study because it brought participants to more severe conditions.
Finally, Bond et al. (4) evaluated the effects of beetroot juice supplementation on rowing performance in 14 well-trained junior male rowers. Similar to the aforementioned studies, this was a 6-day supplementation crossover trial with a 7-day washout period between trials. Rowers consumed either 500 mL per day of beetroot juice or placebo for 6 days. After the supplementation/placebo periods, participants completed 6 maximal 500-m ergometer repetitions. The researchers reported improved 500 meters times with beetroot supplementation; this was particularly observed in the fourth through sixth repetitions.
POSSIBLE NEGATIVE SIDE EFFECTS OF BEETROOT JUICE
There are many positive side effects of beetroot juice. Aside from possibly improving exercise performance, it can possibly reduce blood pressure and it is high in antioxidants. Nonetheless, too much of a good thing can be harmful! One of the most common negative, but not harmful, side effects is beeturia. This is the red coloring of urine that comes from eating beetroot. Other side effects include gastrointestinal upset, increase in blood glucose levels in individuals with diabetes mellitus (because beetroot is high in sugar), and increased risk of kidney stones, especially to those prone to kidney stones, because of the high oxalate content in beetroots. Fevers, chills, and rashes have been reported and may be a sign that the person is allergic to beetroots.
Beetroot juice should not be consumed alone to prevent some of these negative side effects. Combining beetroot juice with other fruits and vegetables, such as carrots and apples, may not only prevent negative side effects but also enhances the flavor.
Finally, it is important that one does not consume beetroot juice on a daily basis. This is important for both variety and to minimize any negative side effects.
Beetroot juice supplementation has been studied in different athletes and, for the most part, has been found to have positive effects on exercise performance, namely, improvement in oxygen consumption, time to exhaustion, or overall time to complete the exercise. Although the studies presented here were well controlled, more research needs to be conducted in larger sample sizes, including women and different types of athletes, to further evaluate its effects on performance. Nonetheless, telling an athlete to “drink beetroot juice” or “increase your beetroot and/or leafy green vegetable consumption” is not such a terrible thing to suggest and may help athletes increase overall vegetable consumption.
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