Turnip the Beet!

My friend Kendall and I were recently grocery shopping for a pre-race meal. When she plopped (expensive) beetroot juice in our cart, I shot her a sideways glance…. “what is that?”.

Kendall was taking an Exercise Physiology class and had learned that beetroot juice contains nitrates, which can be converted by our bodies into nitric oxide, a molecule that not only acts as a neurotransmitter in the central nervous system, but can signal endothelial smooth muscle relaxation (therefore lowering blood pressure) and assist in immune system function (Wylie et al., 2013).  According to her teacher, it also improved performance in endurance athletes. I took her word for it that weekend, but decided to do my own research upon returning home.  

Not shockingly, I found myself completely behind the trend-- the internet is crazy for beetroot juice! Not only Runner’s World Magazine, but Doctor Oz (boo!) and websites like “verywellfit.com” and “eatingwell.com” were endorsing beet root juice. While this craze-status made me more skeptical, I did find several physiology journal articles that examines the effect of beet root juice supplementation in both average to elite athletes, during moderate to intense exercise (however, I will note that all of the studies I found had relatively small sample sizes, with an n of 10-15). One study focused on long-term supplementation, and found that beetroot juice not only decreased overall blood pressure, but also decreased VO_2max during intense exercise, as well as increasing the amount of time athletes lasted during intense exercise (AKA increased “time to failure”) (Wylie et al., 2013).  A second study focused on acute beetroot juice supplementation, meaning subjects were given the supplementation that same day. This study implemented only elite athletes (classifying “elite” based on their VO_2max) (Bescós et al., 2011). Similar to the previous study, the data suggested that beetroot juice significantly lowers VO_2max during high intensity, but not moderate intensity exercise (Bescós et al., 2011). This study did not find a significant difference in time to failure, however.

The exact mechanism behind this improvement is not entirely known. However, exercise physiologists are focusing on the upregulation of the pathway that converts nitrateànitriteànitric oxides that is seen during conditions of hypoxia or acidosis (such as exercise) (Wylie et al., 2013). One hypothesis is that NO assists in wrangling free radicals produced by contracting skeletal muscle (Wylie et al., 2013). Further research will need to be done to understand the relationship between this pathway and hypoxic conditions in skeletal muscle. Meanwhile, beetroot juice has not shown any negative side affects (other than red urine and stool after supplementation…note to self: don’t freak out!), therefore posing little ethical concern to athletes hoping to boost their oxygen processing efficiency. However, one concern is the ethic of non-malfeasance for the hypertensive population. While beetroot juice has proven to reduce blood pressure, this effect may not be sufficient for a person with clinical hypertension (Raubenheimer et al., 2017). Therefore, discussions of this supplementation should be clear about this distinction and encourage patients not to view such supplementation as replacement for prescription medication, especially before discussing with their physicians.

Bescós, R., Rodríguez, F. A., Iglesias, X., Ferrer, M. D., Iborra, E., & Pons, A. (2011). Acute administration of inorganic nitrate reduces VO(2peak) in endurance athletes. Medicine and Science in Sports and Exercise, 43(10), 1979–1986. https://doi.org/10.1249/MSS.0b013e318217d439

Ferrier, D. R. (2014). Biochemistry (6th ed). Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins.

Raubenheimer, K., Hickey, D., Leveritt, M., Fassett, R., Ortiz de Zevallos Munoz, J., Allen, J. D., … Neubauer, O. (2017). Acute Effects of Nitrate-Rich Beetroot Juice on Blood Pressure, Hemostasis and Vascular Inflammation Markers in Healthy Older Adults: A Randomized, Placebo-Controlled Crossover Study. Nutrients, 9(11). https://doi.org/10.3390/nu9111270

Wylie, L. J., Kelly, J., Bailey, S. J., Blackwell, J. R., Skiba, P. F., Winyard, P. G., … Jones, A. M. (2013). Beetroot juice and exercise: pharmacodynamic and dose-response relationships. Journal of Applied Physiology, 115(3), 325–336. https://doi.org/10.1152/japplphysiol.00372.2013