WHAT WE KNOW
Conventional wisdom suggests that pumping iron is good for your muscles, and as it turns out, beets might be a great workout companion. This is because beetroot produces nitric oxide, which has been shown to improve muscle efficiency and endurance exercise tolerance.
Several studies have shown that after anywhere from three to six days of supplementation with beetroot, participants exhibited positive physiological responses to exercise.
Beetroot is also being studied for its effect on blood pressure, with studies showing that after ingestion of dietary nitrate, blood pressure was substantially reduced. Another study documented the effects of beetroot on blood flow to the brain, suggesting that dietary nitrate may be useful in improving brain functioning in older adults.
Energy and Enhanced Exercise Performance
Nitric oxide (NO) plays a role in adaptation to physical exercise by modulating blood flow, muscular contraction and glucose update and control of cellular respiration. In this study, nine young healthy well-trained men performed sub-maximal and maximal work tests after a three-day period of dietary supplementation of sodium nitrate or placebo. The supplementation resulted in lower oxygen demand during sub-maximal work without increasing lactate concentration, indicating that energy production became more efficient.
Eight men aged 19 to 38 consumed 500 ml daily of beetroot juice or placebo for six consecutive days, then completed moderate-intensity and severe-intensity exercises on the last three days. The results showed a significant increase in nitrite concentration and reduced systolic blood pressure. During moderate exercise, there was reduced muscle fractional O2 extraction and an increase in pulmonary O2 update following the onset of moderate exercise during severe exercise, decreased O2 uptake slow component, and longer time to exhaustion.
Bailey, S. J., P. Winyard, A. Vanhatalo, J. R. Blackwell, F. J. Dimenna, D. P. Wilkerson, J. Tarr, N. Benjamin, and A. M. Jones. "Dietary Nitrate Supplementation Reduces the O2 Cost of Low-intensity Exercise and Enhances Tolerance to High-intensity Exercise in Humans." Journal of Applied Physiology 107.4 (2009): 1144–155
This study demonstrated that dietary inorganic nitrate supplementation may improve muscle efficiency and endurance exercise tolerance. The hypothesis was that nitrate supplementation would enhance high-intensity intermittent exercise performance. Fourteen male recreational team sport players randomly consumed 490 ml concentrated nitrate-rich beetroot juice or nitrate depleted placebo juice over 30 h. This study concluded that supplementation promoted nitric oxide production, enhanced test performance by facilitating greater muscle glucose uptake or better maintaining muscle excitability, therefore improving performance during intense intermittent exercise.
Wylie, Lee J., Magni Mohr, Peter Krustrup, Sarah R. Jackman, Georgios ErmÎ¹dis, James Kelly, Matthew I. Black, Stephen J. Bailey, Anni Vanhatalo, and Andrew M. Jones. "Dietary Nitrate Supplementation Improves Team Sport-specific Intense Intermittent Exercise Performance." European Journal of Applied Physiology 113.7 (2013): 1673–684.
In this study, nine healthy, non-smoking volunteers randomly received supplementation or placebo resulting in significant reduction of VO2 max, a measure of the maximum volume of oxygen that an athlete can use, during maximal exercises using large active muscle mass (ie. increased time to exhaustion).
Larsen, Filip J., Eddie Weitzberg, Jon O. Lundberg, and B. Ekblom. "Dietary Nitrate Reduces Maximal Oxygen Consumption While Maintaining Work Performance in Maximal Exercise." Free Radical Biology and Medicine 48.2 (2010): 342–47.
Nine healthy physically active males were randomized to receive 0.5 l beetroot juice per day or placebo for six days in this study, which resulted in increased plasma NO2 concentration and decreased systolic blood pressure. The study concluded that six days of beetroot supplementation had positive effects on physiological responses to exercise.
Lansley, K. E., P. G. Winyard, J. Fulford, A. Vanhatalo, S. J. Bailey, J. R. Blackwell, F. J. Dimenna, M. Gilchrist, N. Benjamin, and A. M. Jones. "Dietary Nitrate Supplementation Reduces the O2 Cost of Walking and Running: A Placebo-controlled Study." Journal of Applied Physiology 110.3 (2010): 591–600.
This study showed that dietary nitrate is favourably associated with nitric oxide-regulated processes, including blood flow and energy metabolism. Researchers found that dietary nitrate supplementation decreases the oxygen cost of human exercise meaning less respiratory activity is required for a set rate of skeletal muscle work.
Affourtit, Charles, Stephen J. Bailey, Andrew M. Jones, Miranda J. Smallwood, and Paul G. Winyard. "On the Mechanism by Which Dietary Nitrate Improves Human Skeletal Muscle Function." Frontiers in Physiology Front. Physiol. 6 (2015): n. pag.
In this double-blind, crossover study, researchers aimed to determine whether whole beetroot consumption, as a means for increasing nitrate intake, improves endurance exercise performance. Eleven recreationally fit men and women were studied in a double-blind, placebo-controlled crossover trial performed in 2010. The study concluded that “consumption of nitrate-rich, whole beetroot improves running performance in healthy adults.”
This study tests the hypothesis that beetroot juice increases the plasma nitric oxide (NO) concentration, which is associated with improvements in cardiorespiratory function at rest and during submaximal aerobic exercise. The subjects were 12 healthy, young adult, normotensive, African-American females. These findings suggest “in healthy subjects, beetroot juice treatments increase plasma NO concentration and decrease cardiac afterload and myocardial oxygen demand at rest and during three submaximal levels of aerobic exercise.”
This article provides a “review of the literature pertinent to the evaluation of the efficacy of nitrate supplementation (from beet juice) in altering the physiological determinants of sport and exercise performance.”
There is ongoing research on the effects of beetroot as it relates to the following health concerns:
In this study, healthy volunteers were given 500 ml of beetroot juice to ingest. It was found that approximately three hours after ingestion of a dietary nitrate load (beetroot juice 500 mL), blood pressure (BP) was substantially reduced (Delta(max) -10.4/8 mm Hg), an effect that correlated with peak increases in plasma nitrite concentration.
Webb AJ, Patel N, Loukogeorgakis S, et al. “Acute blood pressure lowering, vasoprotective, and antiplatelet properties of dietary nitrate via bioconversion to nitrite”. Hypertension. 2008; 51(3): 784–90
In this double-blind, placebo-controlled clinical trial, researchers randomly assigned 68 patients with hypertension to receive daily dietary supplementation for four weeks with either dietary nitrate (250 ml daily, as beetroot juice) or a placebo (250 ml daily, as nitrate-free beetroot juice) after a two-week run-in period and followed by a two-week washout. The findings suggest “a role for dietary nitrate as an affordable, readily-available, adjunctive treatment in the management of patients with hypertension (funded by The British Heart Foundation).”
Kapil V, Khambata RS, Robertson A, Caulfield MJ, Ahluwalia A. Dietary nitrate provides sustained blood pressure lowering in hypertensive patients: a randomized, phase 2, double-blind, placebo-controlled study. Hypertension. 2015;65(2): 320–7.
In this this double-blind, placebo-controlled study, researchers tested the effects of beetroot juice on cardiovascular and metabolic responses to exercise. The findings of this research suggest that “dietary NO3-, administered in the form of beetroot juice (500 ml/day for six days) decreases resting systolic blood pressure (SBP) and O2 consumption during walking and running.”
To evaluate the impact of changes in oxygen tension in the metabolism of NO donors, researchers measured exhaled NO in anaesthetized rabbits in vivo and expired NO and perfusate nitrite (NO2−) in buffer-perfused lungs in situ. In conclusion, the researchers found that “hypoxic conditions preserve very high local NO concentrations generated from organic nitrates in vivo and [they] suggest that this might benefit preferential vasodilation in ischaemic tissue regions.”
Agvald, Per, L. Christofer Adding, Andreas Artlich, Magnus G. Persson, and Lars E. Gustafsson. "Mechanisms of Nitric Oxide Generation from Nitroglycerin and Endogenous Sources during Hypoxiain Vivo." British Journal of Pharmacology135.2 (2002): 373–82.
In this study, researchers investigated the acute effects of beetroot bread (BB) on microvascular vasodilation, arterial stiffness, and blood pressure (BP) in 23 healthy participants. The research concluded that “enriching bread with beetroot may be a suitable vehicle to increase intakes of cardioprotective beetroot in the diet and may provide new therapeutic perspectives in the management of hypertension.”
Hobbs, D. A., M. G. Goulding, A. Nguyen, T. Malaver, C. F. Walker, T. W. George, L. Methven, and J. A. Lovegrove. "Acute Ingestion of Beetroot Bread Increases Endothelium-Independent Vasodilation and Lowers Diastolic Blood Pressure in Healthy Men: A Randomized Controlled Trial." Journal of Nutrition 143.9 (2013): 1399–405.
In this study, the objective was to conduct a systematic review and meta-analysis of randomized clinical trials on 254 participants that examined the effects of inorganic nitrate and beetroot supplementation on blood pressure (BP). The findings suggest “inorganic nitrate and beetroot juice supplementation was associated with a significant reduction in systolic BP”.
Siervo, M., J. Lara, I. Ogbonmwan, and J. C. Mathers. "Inorganic Nitrate and Beetroot Juice Supplementation Reduces Blood Pressure in Adults: A Systematic Review and Meta-Analysis." Journal of Nutrition 143.6 (2013): 818–26.
Blood Flow To The Brain
In this investigation, researchers administered a high- vs. low-nitrate diet (which included beetroot juice) to older adults and measured cerebral perfusion using arterial spin labeling magnetic resonance imaging. These results suggest that “dietary nitrate may be useful in improving regional brain perfusion in older adults in critical brain areas known to be involved in executive functioning.”
T D Presley, A R Morgan, E Bechtold, W Clodfelter, R W Dove, J M Jennings, R A Kraft, S B King, P J Laurienti, W J R ejeski, J H Burdette, D B Kim-Shapiro, G D Miller. “Acute effect of a high nitrate diet on brain perfusion in older adults”. Nitric Oxide. 2011 Jan 1;24(1): 34–42.
Potential Interactions with Warafin and Other Blood-Thinning Medications
In this article, the authors outline uses of Warfarin including: signs and symptoms of bleeding, the impact of diet (including beetroot and its interactions with Warfarin), potential drug interactions, and the actions to take if a dose is missed.
Impact on Metal Accumulating Diseases (porphyria cutanea tarda, hemochromatosis or Wilson disease)
In this study, rats that were fed lyophilised powder of table beetroot (2 g/kg b.w.), which resulted in the accumulation of copper, iron, magnesium, manganese, phosphorus and zinc in the liver. The results suggest caution in patients with metal accumulating diseases such as porphyria cutanea tarda, hemochromatosis or Wilson disease.
Blazovics, Anna, Eva Sardi, Kiara Szentmihalyi, L. Vali, Maria Takacs-Hajos, and Eva Stefanovits-Banyai. "Extreme Consumption of Beta Vulgaris Var. Rubra Can Cause Metal Ion Accumulation in the Liver." Acta Biologica Hungarica 58.3 (2007): 281–86.