Hyped
by athletes and sports physiologists, beets (Beta vulgaris, Chenopodiaceae) have emerged as a trendy and promising
sports performance supplement ingredient. A growing body of evidence suggests that
beetroot, the taproot of the beet plant, has the potential to improve athletic performance
and endurance. New research aims to pinpoint its mechanisms of action, and how it
may help support body systems and impact blood pressure, heart health, and even
cognitive function.
Beetroot
contains a variety of health-promoting compounds, including betaines,
resveratrol, and quercetin. However, studies of the potential sports
performance benefits of beets have focused primarily on nitrates. The nitrates
in beets are converted into nitrite, some of which is then transformed into
nitric oxide, which plays a role in blood pressure regulation, cardiovascular
function, and mitochondrial energy production.
Research
supports certain exercise performance benefits of dietary nitrate
supplementation, with several studies in recent years showing that
supplementation can decrease the oxygen cost of submaximal exercise (exercise
conducted at an intensity less than the maximum of which the individual is
capable) and increase high-intensity exercise tolerance in recreational
athletes.1,2,3 In addition, a 2011 study suggested that nitrate-rich
beetroot juice can increase oxygen efficiency in submaximal cycling exercise.4
Exercise Performance
More
recently, research is honing in on how and when performance is affected by
consumption of beetroot. One 2017 study, led by Oliver Shannon at the Institute
for Sport, Physical Activity and Leisure at Leeds Beckett University in the United
Kingdom, sought to determine the effects of dietary nitrate supplementation on
physiological functioning and exercise performance in trained runners and
triathletes during short- and long-distance time trials. The authors measured
plasma nitrite, resting blood pressure, and maximal oxygen consumption for
eight trained male runners or triathletes. The subjects completed four exercise
performance tests, each consisting of a 10-minute warmup followed by either a 1,500-meter
or 10,000-meter treadmill time test.5 Three hours prior to each
test, the athletes received either 140 mL of concentrated nitrate-rich beetroot
juice or 140 mL of nitrate-depleted beetroot juice. Researchers found that
nitrate-rich beetroot juice supplementation significantly enhanced performance
in the 1,500-meter time trial but not for the 10,000-meter trial.
The
findings, the authors wrote, suggest that beetroot juice supplementation may be
ergogenic (i.e., performance-enhancing) during shorter-distance time trials at
a high work rate, but maybe not during longer-distance time trials at a lower
work rate. The authors also noted that the effects of nitrate supplementation
are highly variable, and that that these results cannot be easily generalized
to other populations or conditions and, as such, further study is warranted.
Much
of the earlier research on beetroot has focused on endurance, but one new study
from 2017 examined the impact of beetroot on high-intensity or
intermittent-type exercise.6 The double-blind, placebo-controlled
crossover study, led by Jean Nyakayiru of the Department of Human Movement
Sciences at NUTRIM School of Nutrition and Translational Research in Metabolism
at Maastricht University Medical Centre in the Netherlands, investigated
whether six days of nitrate-rich beetroot juice supplementation would improve
exercise performance in trained soccer players. Soccer players were chosen
because the sport requires multiple bouts of high-intensity running and a heavy
reliance on type II muscle fibers, which are thought to be the muscle group most
impacted by nitrates.
The
subjects (N = 32), of similar age, height, weight, and playing experience,
ingested two 70-mL doses of beetroot juice (140 mL per day) containing 800 mg
of nitrate or two 70-mL doses of beetroot juice placebo (with similar taste and
appearance but depleted of nitrate) for six days.6 The final dose was
ingested three hours prior to the exercise test. Subjects then completed two
test days of high-intensity intermittent running performance using the Yo-Yo intermittent
recovery level 1 (YoYo IR1) test, a measurement tool that simulates soccer-specific
activities in a controlled setting.
Distance
covered during the test was the primary measure of performance, although heart
rate was measured continuously and blood and saliva samples were taken prior to
the test. The authors found that nitrate-rich beetroot juice ingestion improved
subject performance by 3.4 ± 1.3% compared to the placebo group, with higher
plasma and salivary nitrate concentrations as well.
Interestingly,
mean heart rates in the beetroot juice group were also lower than in the
placebo group during the test. This may have implications for further study on heart
function. The results demonstrate that nitrate supplementation could represent
an effective nutritional strategy to improve exercise performance in soccer
players, especially toward the end of a match. Further study, however, is
needed to see if these same improvements can be translated to athletes at different
performance levels.
Cognitive Function
Beetroot
juice also may have important benefits beyond athletic performance, extending
to healthy aging of the brain and cognitive function. A study published in 2016
examined whether beetroot juice might have a synergistic effect with exercise
on neuroplasticity (i.e., the ability of the brain to reorganize by forming new
nerve cell connections). Led by Meredith Petrie of Wake Forest University in
Winston-Salem, North Carolina, the study looked at the effects of beetroot
juice on the functional brain network of 26 older men (with a mean age of 65.4
years) who were randomly assigned to ingest beetroot juice or placebo for six
weeks of exercise.7
Using
measurements from peak metabolic equivalent capacity and resting state magnetic
resonance imaging, the authors found that the community structure consistency
of the somatomotor cortex (an area of the brain that controls motor signals to
the muscles) was significantly enhanced in the beetroot juice group compared to
placebo.7 They also noted significant differences in the secondary
connections of the brain between the somatomotor cortex and insular cortex.
The
authors concluded that older adults who exercised and consumed beetroot juice
demonstrated greater consistency within the motor community and fewer secondary
connections with the insular cortex compared with those who exercise without
beetroot juice. Because of these results, the researchers wrote that subjects
in “the exercise plus beetroot juice group had brain networks that more closely
resembled those of younger adults, showing the potential enhanced
neuroplasticity conferred by combining exercise and beetroot juice
consumption.”
Conclusion
Though
these studies shed more light on the benefits of beetroot juice and how dietary
nitrates can improve exercise performance and tolerance, many questions remain.
In addition to understanding more about when and how much nitrate-rich beetroot
juice will have an impact, larger studies with more diverse populations are
needed to better understand the exercise advantages and the broader health
benefits of dietary nitrates. Furthermore, there is a wide variation in the
nitrate content of many vegetables, including beets.8 Nitrate must
also be metabolized to nitrite by oral bacteria, so oral hygiene becomes an
important factor in the response to nitrate-based supplements, including
beetroot juice. More safety data would also be useful to understand the effects
of prolonged intake and the advantages or disadvantages of consuming dietary
nitrates from beets alone, as opposed to obtaining the nitrates from other
vegetable sources.
—Karen Raterman
References
- Bailey SJ, Winyard P, Vanhatalo A, et al. Dietary nitrate
supplementation reduces the O2 cost of low-intensity exercise and enhances
tolerance to high-intensity exercise in humans. J Applied Physiol. 2009;107(4):1144-1155.
- Larsen FJ, Weitzberg E, Lundberg JO, Ekblom B. Effects
of dietary nitrate on oxygen cost during exercise. Acta Physiol.
2007;191(1):59-66.
- Bailey S.J., Varnham R.L., DiMenna F.J., Breese B.C.,
Wylie L.J., Jones A.M. Inorganic nitrate supplementation improves muscle
oxygenation, O2 uptake kinetics, and exercise tolerance at high but
not low pedal rates. J
Appl Physiol 2015;118:1396-1405.
- Cermak NM, Gibala MJ, van Loon LJC. Nitrate
supplementation’s improvement of 10-km time-trial performance in trained
cyclists. Int J
Sport Nutr Exerc Metab. 2012;22:64-71.
- Shannon OM, Barlow MJ, Duckworth L, et al. Dietary
nitrate supplementation enhances short but not longer duration running time-trial
performance. Eur J Appl Physiol. April
2017;117(4):775-785.
- Nyakayiru
J, Jonvik KL, Trommelen J, et al. Beetroot juice supplementation improves high-intensity
intermittent type exercise performance in trained soccer players. Nutrients. March 2017;9(3):314.
- Petrie
M, Rejeski WJ, Basu S, et al. Beet root juice: An ergogenic aid for exercise
and the aging brain. J Gerontol A Biol
Sci Med Sci. 2016. doi: 10.1093/gerona/glw219.
- Nuñez
de González MT, Osburn WN, et al. A survey of nitrate and nitrite
concentrations in conventional and organic-labeled raw vegetables at retail. J Food Sci. May 2015;80(5):C942-949.
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