Does Dietary Nitrate from Beetroot Juice Improve Athletic Performance?
Competitive athletes are always looking for an edge. As someone who used to compete in sports such as bicycle racing, swimming, and cross-country skiing, I used to spend countless hours reading about nutrition and ergogenic supplements.
Though there can be certain risks associated with it and I wouldn’t recommend it now, I did win the Provincial Cycling Championships in the Individual Pursuit race following a trial of soda loading with sodium bicarbonate.
Fortunately, there’s been some new emerging research on the performance-enhancing effects of beetroot juice. What’s special about beetroot juice? Beetroot juice contains high levels of anion, nitrate. Dietary nitrate has been studied over the past several years as an ergogenic or performance-enhancing aid.
Basically, the dietary nitrate source is reduced and converted in your body to nitrite (Free Radical Biology & Medicine), then to nitric oxide, NO, and possibly other biologically active nitrogen oxides. This pathway is actually enhanced during times of low oxygen tension and acidosis—which occurs while you’re exercising.
In fact, this initial study found that the nitrate in the equivalent of 100-300 g of nitrate-rich vegetables such as spinach or beetroot when taken in the form, sodium nitrate (.1mmol/kg/day) resulted in a statistically significant trend towards increasing time to exhaustion. In this particular study, there were only 9 healthy volunteers which limited the power of the study.
A previous study involving 8 healthy test subjects (Journal of Applied Physiology) studied the effects of beetroot supplementation for 6 days on its ability to reduce oxygen cost of submaximal exercise and to enhance tolerance to high-intensity exercise. In this study, test subjects consumed 500 ml of beet juice per day which contained (11.2 NM of nitrate). Exercise tests of moderate to high intensity were conducted on the last three of these six days.
The researchers found that this natural source of dietary nitrate resulted in increases in plasma nitrate levels along with modest reductions in blood pressure levels. As well, the researchers found that this supplementation protocol resulted in 16% improvement in time to task failure during the high-intensity testing component.
It should be stressed that the remarkable reduction in the O2 cost of submaximal cycle exercise following dietary supplementation with inorganic nitrate in the form of a natural food product cannot be achieved by any other known means, including long-term endurance exercise training.
How Does Beetroot Juice Improve Performance?
The same researchers from Exeter University conducted a related study to find the mechanistic basis for this increase in performance (Journal of Applied Physiology). They found that the reduced oxygen cost of exercise pertaining to dietary nitrate consumption appears to be related to a reduced ATP (Adenosine Triphosphate) cost for muscle force production. Basically, ATP is an energy molecule used in producing muscular contractions. This research suggests that dietary nitrate supplementation reduces that amount of energy in the form of ATP that you use during exercise.
Dietary Nitrate from L-Arginine Instead?
Again, in another follow-up study, these same researchers from Exeter University conducted a similar study with one small caveat. Instead of supplementing with either beetroot juice or beetroot itself, instead, they used l-arginine. Follow the link for more details on this study as I have discussed it at greater length in a previous blog post. This study used supplementation with 6 grams of l-arginine which increased indices of nitric oxide synthesis. Specifically, the researchers note that interventions that reduce the amplitude of the VO(2) slow component improve tolerance to severe-intensity exercise tolerance. For this study, the time to exhaustion was extended by 26% compared to the placebo intervention.
For those who compete in sports that involve moderate to high-intensity efforts, supplementation with beetroot or beetroot juice seems to be a potent natural way of improving your exercise tolerance.
Keep in mind that all of these studies demonstrated reductions in blood pressure levels in otherwise healthy volunteers. As well, beetroot can also cause some discoloration of your stool by making it appear a reddish color.
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