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- Alex Hutchinson (@sweatscience)
Wow. This study is really impressive. Drinking 500 mL of beet juice 2.5 hours before a cycling time trial improves 4 km TT time by 2.8% and 10 mile TT time by 2.7%. On the one hand, this shouldn’t be surprising, because there have been a bunch of recent studies showing beet juice boosting time-to-exhaustion and reducing oxygen cost… But still, those types of studies often don’t end up translating into real differences in the parameter that matters: actual performance. So, as I said: Wow.
The study, published online last week in Medicine & Science in Sports & Exercise, is legit. It’s from Andrew Jones’s group in Exeter. It’s a properly designed placebo-controlled crossover study. The placebo was beet juice with the nitrates (the active ingredient) filtered out with an ion resin, thus indistinguishable from the active beet juice. The subjects (nine competitive cyclists) visited the lab at least five times before the actual experiment even started, to practice taking the time trials until they achieved repeatability of less than 1%.
To reiterate what’s most striking:
- Performance benefits of 2.8% (6.26 vs 6.45 min) over 4 km and 2.7% (26.9 vs 27.7 min) over 10 miles.
- This improvement was achieved with just one dose of 500 mL of beet juice, taken 2.5 hours before the event. (Note that this dose is equivalent to 1.6 kg of spinach or 3.1 kg of lettuce!)
They also took other measurements: the amount of oxygen used was the same with and without nitrates, but the power generated was higher with nitrates. Also, plasma level of nitrites was higher after the beet juice, consistent with previous studies suggesting that the beet juice works because nitrates are converted to nitrites then to nitric oxide, which lowers the oxygen cost of muscle contractions.
On another note (further to this previous post):
The subjects also abstained from using antibacterial mouthwash and chewing gum during the supplementation periods since these are known to eradicate the oral bacteria which are necessary for the conversion of nitrate to nitrite.
So what more is there to say, other than “Buy stocks in beet juice companies pronto”? Well, one caveat is that it hasn’t yet been shown that these results can be duplicated in elite athletes. It’s notoriously easier to produce big improvements in less-trained athletes, and these subjects were recreationally competitive. So further studies will be required in elites. But it’s time to acknowledge once again that my initial predictions when I first heard about this research in August 2009 were wrong, wrong, wrong!