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Mention the word nitrate and most people think of the pesky preservative found in deli meats, hot dogs, and bacon. The main nitrate used as a preservative is sodium nitrate [there is potassium nitrate as well], an inorganic nitrate mined from the earth. Sodium nitrate converts to sodium nitrite, the active preservative with anti-microbial properties. Nitrite in turn can be converted to nitrosamines under certain conditions, including acidic environments like the stomach. Nitrosamines are also formed under high temperature cooking like when food is charred or overcooked [think hot dogs on a BBQ]. Consequently, food manufacturers add antioxidants like vitamin C and E to help prevent nitrosamine formation.
Because nitrate is the precursor to nitrite which, in turn, is the precursor to nitrosamines, a carcinogen, cured meats, nitrates, and nitrites have all been painted with the same broad ‘pro-cancer’ stroke. The health concern really lies with the nitrosamines. While the jury is still out on whether or not inorganic nitrates, the ones used as preservatives, are a real cancer concern, it’s important not to negatively paint all nitrates and nitrites as ‘bad’.
Nitrates, nitrites and bears, oh my!
It may come as a surprise to most people who a healthy diet that includes lots of vegetables is loaded with nitrates. About 85-90% of the nitrates Canadians consume come from vegetables such as spinach, beets, radishes, lettuce, and celery according to Health Canada’s website where nitrate levels range from 1700 to 2400 mg/kg of food. Unlike the inorganic nitrates mined from the earth, organic dietary nitrates come packaged with a host of other ingredients like fiber, vitamins, minerals, phyto-nutrients and antioxidants. It’s the difference of origin between the two forms of nitrates that appears to make the difference in cancer risk and cardiovascular health. The safety of organic nitrates may be due to the presence of the accompanying nutrients in vegetables or it may be because of how they’re metabolized, it’s unclear.
Why nitrates from vegetables are vital for health
It’s long been known that diets that include plenty of fruits, and more importantly vegetables, are associated with lower rates of cardiovascular disease. Benefits have been attributed to antioxidants, vitamins, or minerals such as potassium, a mineral that helps to effectively lower blood pressure. More recently, leafy green vegetables and beets have been centered out as key players in improved cardiovascular health precisely because of their high nitrate content!
Nitric oxide – a gas you want to produce more of
We’ve known for a while that nitric oxide (NO) helps to lower blood pressure by relaxing blood vessels. The amino acid L-Arginine is converted to NO which is why it’s been used as a non-pharmaceutical agent to manage high blood pressure but a new pathway has been recently discovered – turns out eating lots of nitrate-containing vegetables helps to lower blood pressure by increasing NO production too!
It’s a multi-stepped process: when nitrate-rich vegetables are chewed, bacteria, normally present in the back of the mouth, use the nitrate as energy. As the bacteria use the nitrate, it gets converted into nitrite which builds up in the saliva. When we swallow our food, the nitrite-dense saliva goes with it into the stomach, the perfect low-oxygen, high-acid environment that is needed to convert nitrite into, you guessed it, NO. Once the NO is made, it is rapidly absorbed into the blood stream where it is carried all of the body helping to relax blood vessels along the way and in target organs. What was a complete surprise to researchers was the fact that about 25% of the absorbed nitrates and nitrites travel back to the salivary glands which get excreted back into the mouth, providing an additional source of nitrates and nitrites to ‘keep the NO production system going’ – the sophistication of it all is staggering. Any unused nitrates and nitrites excreted by the kidneys via urine!
Some researchers have speculated that we might be shooting ourselves in the foot in our quest for long-lasting fresh breath. It’s been postulated that our use of anti-bacterial toothpaste and mouthwash, effective at killing the bacteria in our mouths, might in fact be interfering with the NO system by reducing the number of our nitrate-digesting symbiotic allies. A similar concern has been raised regarding the increased use of stomach-acid lowering medications since acid is needed to allow for the conversion of nitrites to NO.