Growing up, one thing that was a given in my Australian household was hearing my mum say, “Eat your greens! They are good for you!” The technical reasons for eating a varied diet full of fruit and vegetables relate to their macro and micronutrient components, along with their fiber content – all of which are critical to consume for good health. What mum did not realize, however, was another reason why eating your greens may be beneficial: Leafy greens contain a compound called nitrates. Turns out these little gems do have a whole lot of benefits, and mum probably never even knew about them!
Nitrates (NO3-) are inorganic components of vegetables that are converted in the human body to nitrites (NO2-) and then Nitric Oxide (NO). NO is a gaseous signaling molecule that results in various critical physiological functions, such as improved blood pressure, neurotransmission, enhanced blood flow to muscles, improved muscle efficiency and better sexual health.
Natural sources of nitrates include celery, arugula, radishes, and spinach. But perhaps the best-known source of nitrates for endurance athletes is the humble beet. This red root vegetable is increasingly found in supplements that promise to deliver a punch of nitrates for better athletic performance – but how does the NO effect work?
What are nitrates, and why do I need them in my diet?
The consumption of nitrates and subsequent formation of NO is considered to be an essential part of human functioning. Nitrates are a direct catalyst for a process called vasodilation. Vasodilation is the widening of blood vessels in the body and this function is paramount to human health, as the process itself is utilized by the body to deliver oxygenated blood to areas that are in greatest need. Increased vasodilation also acts as a transporter for glucose, fats, and other nutrients throughout the body.
The effects of NO can be seen all over the body including in brain function (neurotransmission), wound healing, hemoglobin delivery of oxygen in the blood, blood flow, blood clotting, muscle contractility, glucose sensitivity, and mitochondrial function. It also assists with inflammation control, the body’s immune system, and even penile erectile dysfunction!
The daily consumption goal of nitrates is recommended at 3.7mg/kilogram of body weight, however, the average person only consumes 75mg/day. Putting this in context, a 50kg/110lb athlete should be consuming 185mg per day, while a 75kg/165lb athlete should aim to consume 277.5mg per day.
What do nitrates do for athletes?
When we regularly participate in exercise, training, and sport we invariably become more efficient at the same level of intensity and therefore have a perceived reduction in effort. This takes into account mechanical, neurological, and physiological processes. Consumption of nitrate-containing foods and supplements has been shown to improve the efficiency of working muscles to reduce the work required to achieve the same result. In the context of exercise, it means your athletic capacity can be improved. Breaking it down even further, it means you can go further and longer at the same intensity without fatigue – something pretty much everyone wants when it comes to sports with an aerobic element.
Nitrate supplementation has been shown to reduce the cellular-level adenosine triphosphate (ATP) and PhosphoCreatine (PCr) cost associated with producing muscular contractions, effectively reducing the amount of PCr utilized for the given work completed. Subsequently, nitrates enhance muscle contractile efficiency, in addition to improving the efficiency of the cellular metabolism for energy production (oxidative phosphorylation). In other words, you can perform more contractions with less energy, thus improving your efficiency.
Studies have demonstrated that increased dietary nitrate intake for five to seven consecutive days resulted in more than a fourfold increase in saliva and plasma nitrate, nitrite and subsequent nitric oxide. Through the study of nitrate-rich supplements meeting the criteria of 400mg nitrates, improvements have been shown in the reduced cost of oxygen uptake and improved efficiency in walking, running, rowing, cycling, and repeated sprint exercises.
This improved efficiency is not limited to any particular demographic, with benefits seen in all age groups studied, including untrained males, trained males and females, healthy men and women, along with patients suffering from peripheral artery disease. The benefits of nitrate supplements can assist young and old, male and female and also those individuals who are attempting to adopt a healthier lifestyle.
It should be noted that if you are an elite or highly trained athlete then the results may not be as impressive. Research investigating the effect on professional cyclists has been equivocal and this may be explained by the enhanced physiological system of these athletes and their pre-existing high levels of nitric oxide that is already produced endogenously (inside the body).
Beets – a powerful punch of nitrates
Beetroot (and beetroot powder extracts) happens to be one of the world’s most nitrate-rich vegetables. A high concentration of antioxidant substances called betalains provides many beneficial effects. It is also responsible for the deep red-purple coloration of beetroot. Beets are known to be a rich source of antioxidants and micronutrients including potassium, betaine, sodium, magnesium, vitamin C, and perhaps most notably, inorganic nitrate (NO3). Well-being is very important to us all, now more so than ever. Research has shown consistently that a single-serve or consumption of vegetables or nitrate-containing products can have a beneficial effect on the body, and this is amplified with continual consumption.
What is the optimal dose of beets for athletic performance?
In order to achieve the sports-related benefits of nitrates or beetroot powder, the ideal dose for athletes is higher than the one required to provide basic health benefits. Studies on the optimal dosage of dietary nitrates in regard to enhanced athletic performance suggest 400mg is the magic number.
Studies have revealed that subjects’ athletic performance was enhanced when taking 400mg dietary nitrate supplements for seven consecutive days. This maximizes the levels of nitric oxide (NO) in the body and can lead to results including improved time to exhaustion, improved VO2 by demonstrating a reduced uptake of oxygen for the same amount of work, increased peak power output, improved time trial performance, and repeated sprint efforts.
The other important factor to consider is that peak NO levels will occur around two to three hours after ingestion of a nitrate-containing supplement or food. If you believe your sporting event will require you to have peak levels of NO in your body, aim to time the intake of the nitrate-containing food/supplement accordingly.
For best results, don’t wash your mouth out
A really important consideration when consuming foods or a supplement containing nitrates, like beet juice, is that nitrates are concentrated in your saliva via an active transport system. Nitrates are concentrated at least ten-fold in saliva. It is estimated that up to 25% of dietary nitrates are salvaged during enterosalivary circulation. It is the bacteria in the mouth that convert the nitrates to nitrites and then subsequently to nitric oxide.
Consequently, the use of certain mouthwashes immediately prior to consuming nitrates should be avoided. This is because chlorhexidine-based mouthwashes have been shown to inhibit the body’s response to nitrates and increase blood pressure values in both animal and human studies, implicating the necessity of oral bacteria for nitrate bioactivation. This is not to say you should not brush your teeth after consuming leafy vegetables or a nitrate-containing supplement; we simply advise you not to use mouthwash beforehand.
Beets: Not just for race day
A trend is currently emerging in the nutrition arena that is shifting the focus from all about performance to something more health-centric. This train of thought suggests that diets rich in foods that stimulate nitric oxide bioavailability (e.g., nitrate and nitrite-enriched foods such as leafy green vegetables, beetroot powder extracts, and liquid concentrates) are viable options for seeking a variety of health benefits, not just athletic performance.
Indeed, along with daily physical activity, dietary intake of foods containing nitrates could and should be considered a first-line target for disease prevention. So, while you may be thinking about performance when considering consuming beet-containing products, perhaps first think about the health benefits they are providing as well.
Scott Tindal is a performance nutrition coach with 20 years of experience working with pro and amateur athletes. He has a Masters degree in sports medicine and a post-graduate diploma in performance nutrition. Heis the co-founder of FuelIn, an app-based personalized nutrition coaching program.