• Nitrate: from carcinogen to health and performance booster?

     

    For many years the term “nitrate” was mostly used when discussing the sodium nitrate found in smoked and cured meats. Nitrates and nitrites have been added to cured foods for hundreds of years – they act as antimicrobials, antioxidants, and provide the signature pink color of cured meats.

    In the 1970s, several poorly designed and reported epidemiological studies led to a belief that nitrates and nitrites were carcinogenic. Under certain conditions (high heat, high acidity, and in the presence of certain amino acids), they can be reduced to form nitrosamines, some of which are carcinogens.  However, a few problems existed:

    1. Certain conditions had to be met for nitrosamines to even form,
    2. Any high-heat cooked meat (whether cured or not) can produce nitrosamines,
    3. Nitrates and nitrites helped keep cured meats safer by preventing bacteria and rancidity, and
    4. Far higher amounts of nitrate can occur in certain fruits and vegetables versus cured meats.

     

    Ultimately, nitrate and nitrite were deemed safe in certain amounts (at present the World Health Organization (WHO) and several other organizations maintain maximum recommended daily intakes), and the food industry responded by greatly reducing the amount of the additives in cured meats. In fact, in recent years many cured and smoked meat products have shifted to using natural food sources of nitrate instead of sodium nitrate or nitrite.

    Yes, nitrate and nitrite occur naturally in foods. In fact, the nitrate in foods has become a large topic of interest in the scientific community – not for carcinogenic concerns, but for health and sports performance benefits.

    How Nitrate Functions in the Body

    Before we get into the potential benefits, here is a basic overview of how nitrate and nitrite function in the body:

    1. Nitrate (and nitrite) is consumed orally through the diet.
    2. Bacteria in the saliva convert nitrate to nitrite (note: alcohol-based mouthwash can prevent this reaction from occurring.)
    3. A series of enzymatic reactions reduce nitrite to nitric oxide.
    4. Nitric oxide acts as a signaling molecule for various physiological response, and is also recycled back into the system.

     

    What is the result of this system? Nitric oxide appears to:

    1. Act as a vasodilator, helping to regulate blood flow.
    2. Participate in muscle contractions, in particular the handling of potassium and calcium.
    3. Improve mitochondrial efficiency (the energy powerhouse of cells).

     

    Because of this, nitrate is considered beneficial for cardiovascular health (helping to manage conditions like hypertension) as well as improving exercise performance. Specifically, it seems that nitrates can improve exercise tolerance, endurance performance, and potentially intermittent exercise performance (intervals, team sports, etc.). However, it is not clear whether this is beneficial in both trained and untrained individuals.

    Sources in the Diet

    Vegetables are the predominant source of nitrate in the diet. The vegetables highest in content are arugula, spinach, celery, beetroot, cress, and mustard greens. It’s of interest to note the amount of nitrate in vegetables is much higher than the amount added to cured meats, although the latter has actually increased with the use of natural nitrate sources like celery.

    As a sports performance “supplement”, beetroot juice has become the intake method of choice, and most studies suggest consuming roughly 8 oz of juice twice daily over roughly a week pre-competition. It seems the performance improvements come mostly after a loading period.

    While food and water are sources of nitrate and nitrite, we actually produce much more nitrite on our own. In fact, the daily production of nitrite in our own saliva through the recycling of nitric oxide exceeds the suggested maximum daily intake.  Additionally, the often recommended DASH diet (Dietary Approaches to Stop Hypertension) high in fruits in vegetables is over 500% higher in nitrate intake than the maximum recommended amount by the WHO.

     

    At present, science cannot fully explain the difference between sodium nitrate added to foods (or used clinically) and naturally occurring nitrate. So all of this begs the question on whether or not nitrate and nitrite are indeed harmful at all. Further research will likely explore these issues. Until then, following a diet high in fruits and vegetables with moderate consumption of processed foods like cured meats, along with supplementation of evidence-based products like beetroot juice is a practical approach for both health and performance benefits.

     

    References

    Bailey SJ, Vanhatalo A, Winyard PG, Jones AM. The nitrate-nitrite-nitric oxide pathway: Its role in human exercise physiology. Euro J Sport Sci. 2012; 12: 309-320.

    Bescos R, et al. Sodium nitrate supplementation does not enhance performance of endurance athletes. Medicine and Science in Sport and Exercise. 2012; 12: 2400-2409.

    Cermak NM, Gibala MJ, van Loon LJC. Nitrate supplementation’s improvement of 10-km time-trial performance in trained cyclists. Int J Sport Nutr Exer Metab. 2012; 22: 64-71.

    Hord NG, Tang Y, Bryan NS. Food sources of nitrates and nitrites: the physiologic context for potential health benefits. Am J Clin Nutr. 2009; 90: 1-10.

    Sindelair JJ, Milkowski AL. Human safety concerns surrounding nitrate and nitrite in the diet. Nitric oxide. 2012; 26: 259-266.