Beetroot, a super juice?
Unless you've been
living on Mars for the last couple of years, you'll no doubt be aware that beetroot juice has been creating a stir in sports nutrition circles.
In short, a few days' consumption of beetroot juice seems to produce remarkable physiological benefits for endurance athletes such as cyclists. In particular, by enhancing blood flow in muscles, six days of beetroot juice consumption (half a litre per day) appears to be able to reduce the amount of oxygen needed by exercising muscles to sustain a given sub-maximal (ie not flat-out) workload, thereby increasing the muscles' efficiency and tolerance to high-intensity exercise, and extending endurance.
Scientists believe that it's the very high level of naturally occurring nitrate in beetroot juice that provides these benefits, but there are still a number of questions that need to be answered.
One of the most obvious ones is whether an enhancement in the efficiency of the muscles during sub-maximal cycling actually translates into better performance where it counts - under race or time trial conditions.
To try and answer this question, Dutch scientists have studied the effects of beetroot juice consumption on actual 10km time trial performance in cyclists. Just to reiterate, much of the previous research on beetroot juice has looked at measures such as ‘average power output', ‘cycling efficiency', ‘time to exhaustion' etc.
While these results have all been very encouraging, it's not the same as testing performance under true race conditions. Another variation in this trial was that the cyclists consumed a smaller volume of concentrated beetroot, but which still provided the same nitrate level as 500ml of beetroot juice.
Twelve trained male cyclists performed two trials each separated by 14 days. Each trial consisted of 30 minutes at 45 per cent of maximum power and 65 per cent of maximum power followed by a 10km time trial.
For six days before each trial, the cyclists consumed either 140ml per day of concentrated beetroot juice or the same amount of a placebo, consisting of beetroot juice from which the active ingredient (nitrate) had been removed. The two trials were performed in random order and were ‘double-blind' - here neither the cyclists nor the researchers knew what was being consumed in each of the two trials.
In a nutshell
As in previous studies, the amount of oxygen required to sustain sub-maximal exercise (ie at 45 per cent and 65 per cent of maximum power) was lower when the active beetroot juice was consumed. More importantly, though, was the finding that compared results to the placebo drink.
The active beetroot juice significantly enhanced time trial performance - the average time recorded fell from 965 seconds to 953 seconds. This was confirmed by the fact that the average power output during the time trials rose from 288 watts in the placebo trial to 294 watts in the active beetroot juice trial. Again, this was a significant improvement.
We've said it many times before and we'll say it again - it's very hard to draw firm conclusions from just one scientific study. However, the evidence for the performance benefits of beetroot juice has been rolling in from a number of different studies and this is yet another study confirming those benefits. Although a reduction of 12 seconds over 10km might not sound much, it translates to 19 seconds' improvement over a 10-mile time trial and nearly a minute over a 25-mile time trial - not to be sniffed at!
Int J Sport Nutr Exerc Metab. 2012 Feb 22
This article was first published in the February 9 issue of Cycling Weekly. You can also read our magazines on Zinio and download from the Apple store.