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The story so far: beet juice improves endurance performance. We’re pretty sure it’s because of the nitrate in beets. But we’re not sure whether you can get the same effects by simply taking nitrate supplements directly.
Enter a study in this month’s Medicine & Science in Sports & Exercise, from researchers in Spain. They administered either a placebo or a dose of sodium nitrate (10 mg per kg of body weight) to 11 well-trained cyclists and triathletes. Then, three hours later, the athletes did a series of sub-maximal cycling bouts and a progressive VO2max test to exhaustion. The results: well, this is where it gets confusing:
[W]e found that the VO2peak was significantly reduced when athletes ingested nitrate. These in vivo data were found without any changes in cardiorespiratory and performance parameters, which suggests that nitrate and its reaction products could play an important role in oxygen consumption at maximal intensity of exercise in well-trained athletes.
So basically, in the progressive test to exhaustion, the athletes lasted the same amount of time with or without nitrate (416 seconds with nitrate, 409 seconds with placebo, a nonsignificant difference) — but they reached failure while using less oxygen. So the good news is that nitrate did somehow make the cyclists more efficient at converting oxygen into power. But the bad news is that this didn’t improve their performance — they just used less oxygen.
What to make of this? I’m not sure. That’s partly because the paper is fairly confusing, but I think it’s also because researchers simply don’t know what exactly is going on yet! For practical purposes, my conclusion would be that if you’re looking for a boost, stick with real beet juice rather than sodium nitrate for now. There may be other differences between this study and previous successful performance-boosting studies (e.g. in the training of the subjects, their typical dietary habits and usual nitrate levels, etc.) — but until further studies sort this out, the only thing we know for sure is that beet juice, in some circumstances, works.