Beets have become the “it” vegetable over the past few years as the primary ingredient in Nitric Oxide supplements. Beetroot (BR) juice provides nitrate which converts to nitrite then nitric oxide (NO). The effects on NO occur on a cellular level, and are claimed to ‘enhance’ or increase the number of mitochondria, also known as the powerhouse of a cell. NO reduces the oxygen costs of ATP (energy) production, allowing athletes to maintain the same work rate at a higher intensity of training (1). An athlete will notice this as reduced fatigue when comparing perceived exertion rates and pacing during a temp run. Nitrate has been shown to increase exercise tolerance by 10-20% which translates to a 1-2% improvement in performance (2).
- Cyclists had a 16% improvement in a test to exhaustion after they consumed 17 oz beetroot juice for six days; the test showed a 10 ml/min. increase in oxygen uptake for every one minute of increased workload to exhaustion. (3)
- Runners improved time to complete a 5k after consuming 5 oz of BR (500 mg nitrate), 75 min. before the start of their race (4);
- Cyclists improved time to completion of a 16km time trial by 2.8% after consuming 500 ml BR, 2.5 hrs prior to the start (5);
NO is the end result of two physiological pathways in the body: a) the nitrate-nitrite-nitric oxide pathway, and b) the L-arginine-NO-pathway. The precursors to both pathways can come from food or as part of physiological changes during exercise. During sub-lactate threshold training when there is a high production of hydrogen ions, and your legs feel like their burning as the levels of lactate increases, muscles become acidic. This is the perfect environment for nitrate from food to be converted to nitrite and then reduced to NO. As levels of NO rise, smooth muscle relaxes, allowing blood vessels to dilate and increase the flow of blood to working skeletal muscles. It is the relaxation of muscle and increase in blood flow that contributes to the increased work capacity during exercise, while also decreases blood pressure (6). Unfortunately, NO production begins to decline by the age of 30 and by 60 years old, production of NO is reduced by 80%.
The amino acids L-Arginine and L-Citrulline provide another way for NO to be produced and made available in the body. Levels of L-Arginine decrease during exercise, and cannot keep pace with exercise intensity and/or duration, which is why an exogenous supply of NO is necessary. Consuming foods that contain these amino acids may help increase levels of NO in the body, but depending on the duration of exercise, probably will not be sufficient to improve exercise tolerance.
Food for Fuel
I always recommend optimization of an athletes diet before purchasing supplements. Nitrates are in spinach, arugula, celery, watercress and lettuce but amounts vary depending upon the quality of the soil and when and how the vegetables are harvested. Generally, 200 – 300 grams of these vegetables will provide 500 – 700 mg nitrate. Freezing decreases the nitrate level, and only boil your veggies if you plan on consuming the cooking water.
Consuming a veggie drink that contains spinach, roasted beets, apple, lemon and ginger will provide NO and also a wide variety of antioxidants. This immune support provided by a complete vegetable drink, is ideal to consume during periods of high intensity and/or training volume. If taste is a concern, this can be improved by sweeteners or fruit.
You can also eat foods that contain the amino acid precursors to NO, arginine and citrulline. Arginine is present in nuts, fruits, meats and dairy, and can be converted directly into citrulline and NO inside cells. Enzymes that convert arginine to citrulline, and citrulline to arginine need to function optimally for efficient nitric oxide production. We can protect those enzymes and NO by consuming fruits and vegetables that contain antioxidants (polyphenols, flavonoids, garlic, vitamins C and E).
The challenge with obtaining the amounts of nitrate recommended in research from whole food, is that the amount of nitrate actually present in each food varies depending on harvest, soil and processing. This can be mitigated by consuming a variety of nitrate-rich vegetables several times a week. In terms of overall health, I think this is the best route. It can be argued that taking a BR supplement is more efficient and concentrated because the amount of nitrate/nitrite in each serving is controlled.
Besides the two physiological pathways for NO production, bacteria present in the mouth is also involved in the conversion of nitrates from food to NO. This conversion requires a combination of 15-20 forms of bacteria to be present. Often, the concentration of these bacteria are low due to the use of mouthwash, or antibiotics. If there is insufficient bacteria present, the percent of conversion from nitrate to nitrite is very very low (7). Even when sufficient bacteria are present in the mouth the amount of nitrite converted from nitrate is only 5% and 0.1% of that is converted to NO. This is one of the few times you can claim that bad breath is a performance enhancer! NO production is also activated by acid in the stomach. If levels of gastric acid are low due to chronic use of proton pump inhibitors or antacids, conversion to NO will be limited as well as absorption of nitrate or nitrite from supplements.
If you are wondering if the nitrates present in BR juice are the same substance prohibited in food items as seen on various food labels, and the answer is yes & no. Nitrates were categorized as carcinogenic by the International Cancer Agency in 2006 which is why you will find “No Nitrates Added” written on the label of processed deli meats. Sodium nitrite is added to cured meats and bacon as a preservative, but it is the carcinogenic compound, nitrosamines, that is the concern. Nitrosamines are formed when sodium nitrite reacts with other preservatives, or when the food in which it is in (e.g. bacon) is fried at a very high temperature. Supplement manufacturers would like to have this label removed because nitrates are present in vegetables at much higher amounts. However, common sense tells me that the phytochemicals (anti-cancer) compounds found in vegetables are much more beneficial than cured meats or bacon, and keeping labels on those products may help to limit their intake.
When BR juice supplements were developed four years ago, each serving was at least 500ml/17 oz, tasted very bitter, and had to be taken at least 90 min before exercise. Current supplements are concentrated and crystallized so that one serving is as simple as mixing a packet with fruit juice 30 min. before exercise. Compared to juicing or blending your own vegetable drink, the convenience of taking one serving, sweetened to taste, within 30 min. of your workout, is a simple way to increase NO levels in the body.
Effects on performance are enhanced when a beetroot supplement is consumed daily for a least 15 days (8). I only tried the supplement once, before a very technical 12M trail race in the Colorado Rockies. I cannot attest to the supplement itself, but I did feel more adrenaline than I usually have at the start of the race. There are always pre-race nerves, but they do not feel jittery, which is how I felt after taking the supplement.
Comparing the cost of a 15-day supply of supplement (15 svgs = $52.50) to 15 days worth of fresh produce (15 svgs ($2.00/1 svg) = $30) may be comparable depending on your budget. If you consider yourself a “real food” athlete, you may prefer the whole food route. This would be a good decision because research has found that athletes who already consume a diet high in nitrates from food, often do not respond as well to the supplement. Elite athletes may need to increase the dose of BR juice because their body already has a higher amount of NO metabolites as a byproduct of their training, compared to recreational athletes.
With so many professional athletes promoting the use of BR supplements, they may be hard to resist. If you can afford to spend $50 – $60 for one 15-day dose give it a shot but make sure the product you purchase has been tested for contamination by NSF to avoid a positive doping result. If you already eat a diet full of beets and leafy greens, save the $50 for your next trip to the grocery store or put it towards a much needed massage.
- Larsen et al. Dietary inorganic nitrate improves mitochondrial efficiency in humans. Cell Metab. (2011) Feb 2;13(2):149-59. doi: 10.1016/j.cmet.2011.01.004.
- Wylie et al. Beetroot juice and exercise: pharmacodynamic and dose-response relationships. J Appl Physiol (1985). 2013 Aug 1;115(3):325-36. doi: 10.1152/japplphysiol.00372.2013.
- Bailey et al. Dietary nitrate supplementation reduces the O2 cost of low-intensity exercise and enhances tolerance to high-intensity exercise in humans. J Appl Physiol (1985). (2009) Oct;107(4):1144-55. doi: 10.1152/japplphysiol.00722.2009.
- Murphy et al. Whole beetroot consumption acutely improves running performance. J Academy Nutrition & Dietetics. (2012) Apr;112(4):548-52. doi: 10.1016/j.jand.2011.12.002.
- Lansley et. al. Acute dietary nitrate supplementation improves cycling time trial performance. MSSE. (2011) Jun;43(6):1125-31. doi: 10.1249/MSS.0b013e31821597b4.
- Maher AR, et al. Hypoxic modulation of exogenous nitrite-induced vasodilation in humans. Circulation 2008; 117:670–7.
- Lundberg JO, Weitzberg E, Cole JA, Benjamin N. Nitrate, bacteria and human health. Nat Rev Microbiol. (2004) Jul;2(7):593-602.