There's a lot of buzz about the uses and benefits of beet juice for performance. In this article, Joe McQuillan PhD (at the time a PhD candidate) looks at some of the research on beets and performance
Joe McQuillan PhD
Recently, two research articles presented evidence for increased time-trial performance in well-trained cyclists (relative VO2max ~57 ml/kg/min) following dietary nitrate supplementation using beetroot juice.
If you have been following the time-line of beetroot juice as a method to enhance stamina or decrease the cost of exercise you would know there is nothing unusual about the findings—aside from the fact it was carried out on trained cyclists. To ensure transparency of findings both studies utilized a double-blind (researchers and subjects are not aware of whether the drink is nitrate rich or nitrate depleted), repeated measures cross-over (subjects carried out all testing under nitrate rich and nitrate depleted conditions). Diets were also closely monitored so that prior to testing cyclists did not alter their diet in any way, thus reducing the possibility for external alterations to changes in performance.
The choice of drink in both studies was James White Drinks organic beet-it juice, however the two studies employed quite marked loading protocols with Cermak et al (2011) using a 6-day chronic loading phase using 140 ml/day at a concentration of 8.0 mmol. In the second reviewed study, Lansley et al (2011) used 500 ml of 6.2 mmol concentration taken as an acute dose 2.5 hours prior to the 4 km and 16.1 km time-trial. Table 1. details the characteristics of participants, the loading protocols and changes in performance over 4 km,10 km and 16.1 km distance following dietary nitrate supplementation.
While previous studies have shown changes in performance using ‘healthy’ populations this is the first evidence that dietary nitrate supplementation via natural beetroot juice can enhance performance in a trained group of athletes. A reduction of time by 1% will result in a 34 sec reduction for a 60 min time-trial. To achieve this from as a result of a ‘training effect’ for an already well-trained athlete would require either an increase in training time, change in methodology of training or—if this option exists in the sport – purchasing equipment to go faster or all of the above.
Within their study, Cermak et al (2011) also investigated the impact of nitrate supplementation on two bouts of 30 mins of steady state cycling. To achieve this, participants cycled on an ergometer at 45% and 65% of their peak power output (PPO) based on a previous incremental cycle test. Their ventilation response was measured during this time in order to assess a variety of breathing responses including oxygen (VO2) utilisation and carbon dioxide production (VCO2). As witnessed in previous papers a reduction in VO2 was accompanied by no change in VCO2, total energy utilization, heart rate or rate of perceived exertion. The magnitude of the reduction of VO2 at 45% PPO was 3.5% and at 65% PPO it was 5.2%. Therefore at greater relative intensities, dietary nitrate appears to have a greater effect on enhancement of exercise economy. It would appear that the combined effects of vasodilation, alterations within the mitochondria and improved ATP efficiency are – at least in part—responsible for these physiological improvements which lead to the performance improvements witnessed in the three details time-trials.
The relatively large dosage of Cermak et al (2011) equates to a nitrate intake of ~500 mg. I say relatively large as to ingest the same amount of nitrate through raw vegetables would require eating ~3 moderate lettuces in one sitting. Healthy, yes, but quite impractical as a loading strategy and in the lead up to competition. Obviously, with no preparation required and ease of ingestion 2.5 hours out from an event the beetroot juice is formulated for a sporting focused market. With these relatively new findings expect to see an increasing number of cyclists, runners, multisporters and triathletes of all abilities consuming beetroot juice before their peak events.