Scientists from Sheffield Hallam University report that 140 mL per day of the beetroot drink was associated with trends to reduce not only 5 km time trial performance, but also systolic blood pressure.
“Although not statistically significant, these results suggest beetroot juice supplementation improved 5 km time trial performance over PLA by 31 s (2.4%),” they wrote in the British Journal of Sports Medicine . “Athletes should consider ingesting beetroot juice to improve 5 km running performance.”
Building the science
Science to support the potential for sports nutrition and cardiovascular health benefits of beetroot juice has been building in recent years, with UK scientists leading the charge. Scientists at the University of Exeter in the UK reporting that beetroot juice may boost stamina and allow people to exercise for up to 16% longer.
The vegetable juice’s nitrate content may reduce oxygen uptake to an extent that cannot be achieved by any other known means, making exercise less tiring, according to findings published in the Journal of Applied Physiology (doi:10.1152/japplphysiol.00722.2009).
“Our study is the first to show that nitrate-rich food can increase exercise endurance,” said Professor Andy Jones, the lead researcher of that study. “We were amazed by the effects of beetroot juice on oxygen uptake because these effects cannot be achieved by any other known means, including training.”
Improvements in the performance of cyclists have also been reported by scientists from the University of Maastricht .
Robyn Lanceley and her co-workers used a double-blind, repeated-measures crossover design with a 14 day washout period to examine if beetroot juice supplementation would affect on 5 km running time trial performance.
They recruited 11 trained female runners (average age 20) and assigned them to receive 140 mL of the beetroot juice per day, compared to a placebo and no supplementation.
Results showed that there were no significant changes in systolic blood pressure between the groups, but there was a trend toward greater reduction following the beetroot juice consumption, with an average value of 114 mmHg, compared with 122 mmHg and 120 mmHg following the control and placebo interventions respectively.
In addition, while no statistically significant changes were observed for 5 km time trial performance the trend was again towards reductions following beetroot juice consumption. Indeed, times were 49 seconds and 31 seconds quicker following the beetroot juice consumption, compared to control and placebo, respectively.
“One km split times were similar between conditions except for the 2nd km where beetroot juice was faster than control by 16 seconds and placebo by 12 seconds,” they added.
Scientists have previously reported that between 20 and 25% of the nitrate we ingest is secreted in saliva, and about 20% of this is converted to nitrite by bacteria on the tongue, resulting in nitrite-rich saliva. This is then swallowed and absorbed in the stomach and enters the circulation where NO synthesis occurs by the reduction of nitrite within the blood vessel wall and erythrocytes.
This nitric oxide is postulated to result in vasodilation within the microcirculation to produce a decrease in peripheral resistance and therefore a reduction in blood pressure.
Source: British Journal of Sports Medicine
2013 Nov, Volume 47, Number 17:e4, doi: 10.1136/bjsports-2013-093073.8.
“Effects of dietary nitrate supplementation on 5 km running time trial performance in trained female runners”
Authors: R. Lanceley, M. Ranchordas, A. Ruddock