Some science behind the scenes

Sodium nitrite

Sodium nitrite is the inorganic compound with the chemical formula NaNO2. It is a white to slightly yellowish crystalline powder that is very soluble in water and is hygroscopic.

It is used as a precursor to a variety of compounds, such as pharmaceuticals and pesticides.  It is used in making dyes and rubber, in photography, in electrochemical grinding manufacturing processes.  It is used in a variety of metallurgical applications, for phosphatizing and detinning.  Sodium nitrite is an effective corrosion inhibitor and is used as an additive in industrial greases, as an aqueous solution in closed loop cooling systems, and in a molten state as a heat transfer medium.

And believe it or not, it is on the World Health Organization's List of Essential Medicines, when it is used together with sodium thiosulfate to treat cyanide poisoning.  It is in the section "antidotes and other substances used in poisonings".

Curing

In the early 1900s, ‘irregular curing’ was commonplace. Salt, molasses, treacle, all manner of natural substances were used to cure meat.  The main problem is that it didn’t always work and in the days before canning and freezing, meat could become rancid and worse – harbour ‘germs’.

It had been noticed that sodium nitrite inhibited the growth of disease-causing microorganisms; and inhibited lipid oxidation that led to rancidity and so without further ado and with no tests on food safety whatsoever, it started to be used in the food processing industry.  It even has the E number E250. Potassium nitrite (E249) is used in the same way. It is approved for usage in the EU, USA and Australia and New Zealand.

Sodium nitrite does indeed inhibit the spores of growth of Clostridium botulinum in refrigerated meats. The mechanism for this activity results from the inhibition of iron-sulphur clusters essential to energy metabolism of Clostridium botulinum.  Sodium nitrite is also able to effectively delay the development of oxidative rancidity.   Sodium nitrite acts as an antioxidant and reacts with heme proteins and metal ions, neutralizing free radicals by nitric oxide (one of its by-products). Neutralization of these free radicals terminates the cycle of lipid oxidation that leads to rancidity.

However, sodium nitrite’s effectiveness is a good deal less certain when it comes to controlling growth of other spoilage or disease causing microorganisms.  The inhibitory mechanisms for sodium nitrite are not known.  Furthermore, it is generally agreed that sodium nitrite is not considered effective for controlling gram-negative enteric pathogens such as Salmonella and Escherichia coli.

And conning

Fresh meat is pink or red.  Once it ages it starts to go a more muted, even grey colour.  Food processing companies then started to realise that they could make their old meat look all fresh and newly butchered, by treating it with Sodium nitrite which gives it that desirable red or pink colour.  In other words it is a con, old stale meat can be passed off as fresh meat.   Very little nitrite is needed to induce this change.
It has been reported that as little as 2 to 14 parts per million (ppm) is needed to induce this desirable color change. However, to extend the lifespan of this color change, significantly higher levels are needed.

The mechanism responsible for this colour change is the formation of nitrosylating agents by nitrite, which has the ability to transfer nitric oxide that subsequently reacts with myoglobin to produce the cured meat color.

The unique taste associated with cured meat is also affected by the addition of sodium nitrite.  However, the mechanism underlying this change in taste is not understood”.

Food containing nitrites

 In the U.S., meat cannot be labelled as "cured" without nitrite addition.  It is found in some [not all] sorts of bacon, sausages, mince, hamburgers, cured dry sausages, pepperoni, cured sandwich meats and some salami.  It is found in some corned beef. Nitrite is also used as a food additive in some fish and cheese products.

Because of the relatively high toxicity of nitrite (the lethal dose in humans is about 22 milligrams per kilogram of body weight), the maximum allowed nitrite concentration in meat products is 200 ppm.

Nitrites are not naturally occurring in vegetables in significant quantities. However, nitrates are.  Please notice the difference.  A study in northern Portugal found residual nitrate levels in 34 vegetable samples, including different varieties of cabbage, lettuce, spinach, parsley and turnips ranged between 54 and 2440 mg/kg, e.g. curly kale (302.0 mg/kg) and green cauliflower (64 mg/kg). Boiling vegetables lowers nitrate but not nitrite.

The link with cancer

Under certain conditions – especially during cooking – nitrites in meat can react with degradation products of amino acids, forming nitrosamines, which are known carcinogens, for example.

  • increased consumption of nitrites …. seemed to be risk factors for gastric cancer. PMID:  26633477
  • The authors evaluated the relation of dietary nitrate and nitrite to pancreatic cancer risk in the NIH-AARP Diet and Health Study. … During approximately 10 years of follow-up between 1995 and 2006, 1,728 incident pancreatic cancer cases were identified. … men in the highest quintile of summed nitrate/nitrite intake from processed meat had a nonsignificantly elevated risk of pancreatic cancer … The authors observed a stronger increase in risk among men for nitrate/nitrite intake from processed meat at ages 12-13 years PMID:  21685410

The thyroid

What is perhaps less known is that nitrites can also affect the thyroid

The potential effects of inorganic nitrate/nitrite on global health are a much debated issue. In addition to possible methemoglobinemia and carcinogenic properties, anti-thyroid effects of nitrate/nitrite have been suggested. Considering the growing significance of nitrate/nitrite and since there is no comprehensive review in data available, clarifying the effect of nitrate/nitrite on thyroid disorder outcomes is essential. Therefore, we conducted this systematic review of experimental and clinical studies, and a meta-analysis of relevant cohort and cross-sectional studies investigating the association of nitrate/nitrite exposure and thyroid function. Most animal studies show that high exposure (~10-600 times of acceptable daily intake) to nitrate/nitrite induces anti-thyroid effects, ……; findings from three cohort studies showed a significant association between higher exposure to nitrite and the risk of thyroid cancer (risk = 1.48, 95% confidence interval = 1.09-2.02, P = 0.012). PMID:  25889269


Oxygen deprivation

Because of sodium nitrite's high level of toxicity to swine (Sus scrofa) it is now being developed in Australia to control feral pigs and wild boar. The sodium nitrite induces methemoglobinemia in swine, i.e., it reduces the amount of oxygen that is released from haemoglobin, so the animal will feel faint and pass out, and “then die in a humane manner after first being rendered unconscious.”  So far no one has made the connection between pigs and human beings, but one assumes it is only a matter of time.

Migraines

Sodium nitrite consumption has also been linked to the triggering of migraines in individuals who already suffer from them.  I think the connection between oxygen deprivation as described above and headaches which can be caused by oxygen deprivation, may be apparent.

COPD

One study has found a correlation between highly frequent ingestion of meats cured with pink salt and the COPD form of lung disease. The study's researchers suggest that the high amount of nitrites in the meats may have been responsible. Again the link may be oxygen deprivation.

References

  • Nitric Oxide. 2015 May 1;47:65-76. doi: 10.1016/j.niox.2015.04.002. Epub 2015 Apr 15.  Is dietary nitrate/nitrite exposure a risk factor for development of thyroid abnormality? A systematic review and meta-analysis. - Bahadoran Z1, Mirmiran P2, Ghasemi A3, Kabir A4, Azizi F5, Hadaegh F6. DOI: 10.1016/j.niox.2015.04.002
  • Lancet. 1972 Dec 2;2(7788):1162-3.  "Hot-dog" headache: individual susceptibility to nitrite.  Henderson WR, Raskin NH.  PMID:  4117590

Observations

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