Everything you wanted to know about nitrates

Most likely, nitrates are not associated with dinner, but evoke thoughts about school chemistry lessons or fertilizers. If you think of nitrates in the context of food, the most likely negative image that comes to mind is that in processed meats and fresh vegetables, nitrates are carcinogenic compounds. But what are they really and are they always harmful?

In fact, the link between nitrites/nitrates and health is much more subtle than just “they are bad for us”. For example, the high natural nitrate content of beetroot juice has been linked to lower blood pressure and increased physical performance. Nitrates are also the active ingredient in some angina medications.

Are nitrates and nitrites really bad for us?

Nitrates and nitrites, such as potassium nitrate and sodium nitrite, are naturally occurring chemical compounds containing nitrogen and oxygen. In nitrates, nitrogen is bonded to three oxygen atoms, and in nitrites, to two. Both are legal preservatives that inhibit harmful bacteria in bacon, ham, salami, and some cheeses.

But in fact, only about 5% of the nitrates in the average European diet come from meat, more than 80% from vegetables. Vegetables acquire nitrates and nitrites from the soil in which they grow. Nitrates are part of natural mineral deposits, while nitrites are formed by soil microorganisms that break down animal matter.

Leafy greens such as spinach and arugula tend to be the top nitrate crops. Other rich sources are celery and beetroot juice, as well as carrots. Organically grown vegetables may have lower nitrate levels because they do not use synthetic nitrate fertilizers.

However, there is an important difference between where nitrates and nitrites are found: meat or vegetables. This affects whether they are carcinogenic.

Association with cancer

Nitrates themselves are fairly inert, which means they are unlikely to be involved in chemical reactions in the body. But nitrites and the chemicals they produce are much more reactive.

Most of the nitrites we encounter are not consumed directly, but are converted from nitrates by bacteria in the mouth. Interestingly, studies show that the use of an antibacterial mouthwash can reduce oral nitrite production.

When the nitrites produced in our mouth are swallowed, they form nitrosamines in the acidic environment of the stomach, some of which are carcinogenic and have been linked to bowel cancer. But this requires a source of amines, chemicals found in abundance in protein foods. Nitrosamines can also be created directly in food through cooking at high temperatures, such as frying bacon.

“Nitrates/nitrites that are carcinogenic are not many, but how they are prepared and their environment is an important factor. For example, nitrites in processed meats are in close proximity to proteins. Particularly for amino acids. When cooked at high temperatures, this allows them to more easily form cancer-causing nitrosamines,” says Keith Allen, executive director of science and public relations for the World Cancer Research Foundation.

But Allen adds that nitrites are just one of the reasons processed meat promotes bowel cancer, and their relative importance is uncertain. Other factors that may contribute include iron, polycyclic aromatic hydrocarbons that form in smoked meat, and heterocyclic amines that are created when meat is cooked over open flames, which also contribute to tumors.

Good chemicals

Nitrites aren’t that bad. There is growing evidence of their benefits for the cardiovascular system and beyond, thanks to nitric oxide.

In 1998, three American scientists received the Nobel Prize for their discoveries about the role of nitric oxide in the cardiovascular system. We now know that it dilates blood vessels, lowers blood pressure, and fights infections. The ability to produce nitric oxide has been linked to heart disease, diabetes, and erectile dysfunction.

One way the body produces nitric oxide is through an amino acid called arginine. But it is now known that nitrates can significantly contribute to the formation of nitric oxide. We also know that this may be especially important for older adults, as natural nitric oxide production via arginine tends to decline with aging.

However, while the nitrates found in ham are chemically identical to those you might eat with a salad, plant-based ones are best.

“We observed increased risks associated with nitrate and nitrite from meat for some cancers, but we did not observe risks associated with nitrate or nitrite from vegetables. At least in large observational studies where consumption is estimated from self-report questionnaires,” says Amanda Cross, lecturer in cancer epidemiology at Imperial College London.

Cross adds that it’s a “reasonable assumption” that the nitrates in leafy greens are less harmful. This is because they are rich in protein and also contain protective components: vitamin C, polyphenols and fibers that reduce the formation of nitrosamine. So when most of the nitrates in our diet come from vegetables and in turn stimulate nitric oxide formation, they are probably good for us.

One nitric oxide expert went further, arguing that many of us are deficient in nitrates/nitrites and that they should be classified as essential nutrients that can help prevent heart attacks and strokes.

The right amount

It is practically impossible to reliably estimate dietary intake of nitrates because dietary levels of nitrates are highly variable. “Levels can change 10 times. This means that studies examining the health effects of nitrate must be interpreted very carefully, as “nitrate” could simply be a marker of vegetable consumption,” says nutritional epidemiologist Günther Kulne from the University of Reading in the UK.

A 2017 report by the European Food Safety Authority approved an acceptable daily amount that can be consumed over a lifetime without appreciable health risk. It is equivalent to 235 mg of nitrate for a 63,5 kg person. But the report also notes that people of all age groups can exceed this number quite easily.

Nitrite intake is generally much lower (average UK intake is 1,5mg per day) and the European Food Safety Authority reports that exposure to nitrite preservatives is within safe limits for all populations in Europe, except for a slight excess. in children on diets high in supplements.

Some experts argue that the daily allowance for nitrates/nitrites is outdated anyway, and that higher levels are not only safe, but beneficial if they come from vegetables rather than processed meats.

It has been found that the intake of 300-400 mg of nitrates is associated with a decrease in blood pressure. This dose can be obtained from one large salad with arugula and spinach, or from beetroot juice.

Ultimately, whether you take a poison or a medicine depends, as always, on the dosage. 2-9 grams (2000-9000 mg) of nitrate can be acutely toxic, affecting hemoglobin. But that amount is hard to come by in one sitting and very unlikely to come from the food itself, rather from fertilizer-contaminated water.

So, if you get them from vegetables and herbs, then the benefits of nitrates and nitrates almost certainly outweigh the disadvantages.

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