Nitrates are inorganic compounds found in many vegetables such as spinach, celery, radishes, and lettuce, but beetroot is one of the highest sources. Nitrate contributes to the production of nitric oxide, which has an important role to play in immune function as well as regulating the tone of blood vessels which impacts blood pressure. In this podcast, I look at the evidence for using nitrate-rich beetroot juice to treat high blood pressure as well as its role as a supplement to improve athletic performance.
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Nitrates are inorganic compounds found in many vegetables such as spinach, celery, radishes, and lettuce, but beetroot is one of the highest sources. Nitrate contributes to the production of nitric oxide, which has an important role to play in immune function as well as regulating the tone of blood vessels which impacts blood pressure. In this podcast, I look at the evidence for using nitrate-rich beetroot juice to treat high blood pressure as well as its role as a supplement to improve athletic performance.
Links referred to in the podcast
Episode transcript
To access the full episode transcript, go to the following link and select the individual podcast episode and then click on the ‘Transcript’ tab https://thinkingnutrition.buzzsprout.com
Connect with me
Instagram: doctimcrowe
Facebook: Thinking Nutrition
Twitter: CroweTim
Nitrates are inorganic compounds found in many vegetables such as spinach, celery, radishes, and lettuce, but beetroot is one of the highest sources. Nitrate contributes to the production of nitric oxide, which has an important role to play in immune function as well as regulating the tone of blood vessels which impacts blood pressure. In this podcast, I look at the evidence for using nitrate-rich beetroot juice to treat high blood pressure as well as its role as a supplement to improve athletic performance.
Beetroot juice is getting a lot of attention. With claims that it can boost stamina to help you exercise longer, improve blood flow, and help lower blood pressure, there is a growing dossier of clinical evidence to help support these claims.
And it’s all thanks to natural chemicals called nitrates that are found in beetroots. Though green leafy vegetables such as spinach and lettuce, along with radishes and even parsley are all good sources too.
Nitrate is converted in the mouth and stomach to a potent chemical called nitric oxide. Nitric oxide has many roles in the body, but its most important role relates to acting as a vasodilator where it opens up blood vessels - allowing more blood and oxygen to flow to the muscles. A positive side effect of this vasodilation can be a fall in blood pressure.
Nitrate may also reduce the energy cost of exercise and positively affect muscle contraction. Hence the dual interest in nitrates as a way to treat high blood pressure, as well as its use as a sports supplement to improve athletic performance.
First, let’s tackle high blood pressure, also known as hypertension. High blood pressure can result from a gradual ‘hardening’ of the arteries that can make them more resistant to dilation. This loss of elasticity over time increases resistance to the force exerted by the flowing blood, resulting in an increase in blood pressure.
So in adults with hypertension, are the nitrates from beetroot juice able to have a significant effect on reducing blood pressure? That was the topic of a recently published systematic review. And I’ll link to this review in the show notes. https://pubmed.ncbi.nlm.nih.gov/35369064
The review included 7 randomised-controlled trials that had over 200 adults with hypertension take between 70 and 250 mL of beetroot juice or a placebo beetroot juice drink that had its nitrate content depleted. The trials ran for between 3 and 60 days.
Overall, there was a small benefit when taking the nitrate-rich beetroot juice. With a significant fall in systolic blood pressure (which is the higher of the two readings when blood pressure is reported such as for example 120 over 80) and this fall was in the range of 5 mmHg. For the diastolic reading, which is the lower number, there wasn’t much evidence for a drop.
But it was interesting that the results varied depending on the setting where the blood pressure was measured. Blood pressure data collected in a clinical setting (such as a doctor’s surgery) was more likely to show a fall compared to blood pressure readings taken in a more free-living ambulatory setting using 24-hour monitoring equipment. This could be related to a measurement artefact or an issue with doing sub-group analysis meaning you have less data to analyse compared to pooling all the data together.
But it does appear that nitrate-rich foods such as beetroots can have a small benefit on blood pressure which could be important when added to other positive lifestyle changes such as exercise, quitting smoking, drinking less alcohol and of course: eating healthier. No surprise that all the nitrate-rich foods are healthy for a whole bunch of other reasons too.
Sports performance
Okay, so that’s the clinical side of nitrates covered. So, what about for those who are looking to gain a performance edge in their sport? What does nitrate-rich beetroot juice have to offer you?
If you don’t follow the world of sports supplement research very closely, your reaction to knowing that athletes are chugging down shots of beetroot juice may be along the lines of: “What sorcery is this?” But this is not some faddish trend like Rubik’s cubes, finger spinners or activated almonds. There is now good science to show that beetroot juice, or more specifically those nitrates in it and the nitric oxide made from it, can have a significant benefit on sports performance.
Nitric oxide is a potent vasodilator, meaning it improves blood flow and oxygen delivery to working muscles. Nitric oxide thus improves the muscles’ efficiency in using oxygen. Nitric oxide also augments exercise performance by the enhanced function of type II muscle fibres which are the fast-twitch muscles used in powerful bursts of movements like sprinting. And finally nitrate, through nitric oxide, can result in a reduction in the energy cost of muscle contraction and increased efficiency of mitochondrial respiration. This all means the muscles are finely tuned for explosive power when oxygen levels are limited.
So, will drinking beetroot juice improve athletic performance? With several dozen exercise studies looking at beetroot juice and nitrates and sports performance now published, the results are looking very promising. In fact, nitrates were one of the few supplements to get the tick for having good evidence behind it in the 2018 IOC Consensus Statement on dietary supplements for use by high-performance athletes and I’ll link to this document in the show notes https://bjsm.bmj.com/content/52/7/439
So, let’s go over a summary of those benefits. Athletes who supplement with beetroot juice which contains an adequate amount of nitrate, on average gain a small benefit on exercise endurance. The most commonly studied exercise situations have been cycling and running trials from about 4 to 30 minutes in duration. At an elite level, clinical trials show a small, but competitively meaningful benefit in time trial performance. Recreational athletes seem to gain an even greater benefit from beetroot juice, which could be because of less prior adaptation of their cardiovascular system to exercise.
Taking on extra nitrate in the form of beetroot juice can improve the exercise economy of athletes when working at a constant load while running or biking, which translates into a slightly longer time until exhaustion. So, for endurance athletes, this could convert into a small competitive advantage.
Supplementation is also seen to improve performance in high-intensity, intermittent, team-sport exercise of 12 to 40 minutes in duration.
Beetroot juice appears to have little effect on power output but seems to reduce the rate of fatigue seen with continued muscle contractions. That means beetroot juice has the most benefit in exercise ranging from 1 minute up to 10 minutes or for muscular endurance events such as sports requiring anaerobic intervals such as football, hockey or rugby, and CrossFit-type exercises.
Typical doses of nitrate used in research studies have been in the ballpark of 400 mg. This dose can be provided by a single-serve of a commercial beetroot juice 'shot' of about 70 mL taken about 2 to 3 hours before exercise.
The highest dietary sources of nitrate are beetroot, celery, lettuce, and spinach. They contain about 250 milligrams of nitrate per 100 grams, but levels can vary hence the popularity of the commercial beetroot shots. And even though beetroot juice can be made at home with a juicer, the concentrated shots are generally more popular owing to the much lower volume required than DIY juices. For the same amount of nitrate as you would get in a commercial 70 mL beetroot shot, you would have to chug down about half a litre of beetroot juice, which may not be too appetising an hour before a race.
As a side note, athletes using beetroot juice should avoid using mouthwash or gum as they reduce the bacteria available in the mouth that are essential for the conversion of nitrate to nitric oxide.
So, let’s wrap all this up. There is little concern about harmful effects from taking beetroot juice apart from some occasional minor gastrointestinal upsets. But as anyone who has tried beetroot juice will tell you though, be prepared for a ‘colourful surprise’ on visits to the bathroom – what goes in purple comes out pink. But this pink colouration of the urine and stools is temporary and harmless.
So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.
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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.