One of the questions I get asked most often is wether or not I use nitrates in the curing of my meats. It is a very controversial subject and I will try to put as many facts together in this post so you can decide for yourself. One gentleman who shall remain nameless decided to debate the issue with me on a Sunday night via SMS and he clearly was far more interested in fighting than listening which might be due to the fact that he had no facts to back up his statements. He would not reveal his identity but I managed to track him down , posted some articles of interest and since then he has gone quiet.
What is it and why do we use it…….
Centuries ago the preservation of meat was found to be improved with the addition of saltpetre (potassium nitrate). This most likely occurred by accident and the exact events are unknown however since Roman times nitrates have been added to cured meats to prevent bacterial spoilage, control rancidity and preserve the colour of the meat (3). Today we use sodium nitrate and nitrite and it goes by many names – pink salt, Prague powder, Quick Cure or Quick Red. To give you an idea of the amounts used for 1000g of meat we use 0,08g of nitrate and 0,08g of nitrite. These amounts are too small to accurately weigh out and so the nitrates are combined with normal table salt. The name pink salt derives from the colour as a red dye is added to the salt to prevent it being mistaken for ordinary salt.
How does it work…..
I'm not a scientist nor a food technologist so here is a lay man explaining the process: The added nitrites are converted to nitric oxide. Nitric oxide combines with the myoglobin found in the meat to form nitric oxide myoglobin which is a deep red colour (1). Any added nitrates are converted to nitrites by bacteria and then are converted to nitric oxide. For products with a long curing time, adding nitrates and nitrites is recommended as the nitrates convert to nitrites over time and provide a longer lasting supply of nitrites. At the same time salt (sodium chloride) is added to the meat to dry out the moisture that many bacteria require to thrive.
So why the bad rap…..
Three reasons. Firstly in the 1950s in America infants fed formula from contaminated water were found to have methemoglobinemia (blue baby syndrome) and cyanosis. In essence their blood was unable to carry oxygen. The high levels of nitrates in the water was thought to have caused this and as a result the EPA reduced the recommended intake of nitrates. Subsequently it was discovered that the wells were contaminated with fecal matter and that was more likely to be the cause of the methemoglobinemia. (4)
The second reason is that nitrites can under certain conditions be converted to nitrosamines which can be carcinogenic. These conditions require that secondary amines are present in the meat, the pH is nearly neutral and the product temperature is above 130C as would be the case when frying bacon at high heat. The studies on nitrosamines were conducted on animals and the effects on humans is uncertain due to the high levels and specific amines used. Nitrates and nitrites on their own have not been proven to be carcinogenic. (4)
The third reason are the findings of Jiang et al (6,7,8) regarding the consumption of cured meats and the link to chronic obstructive pulmonary disease. They have associated the nitrites in cured meats with damage to the lung without considering that most nitrites ingested come from vegetables and drinking water and additionally the subjects with a higher risk had a higher total energy intake, lower physical activity, higher BMI and higher exposure to smoking.
However did you know….
Vegetable are estimated to contribute 80% of the nitrites we ingest (3)
Plants absorb nitrates from fertiliser
Spinach, celery, radish and beets contain far higher levels of nitrates that cured meats (3)
Saliva converts nitrates to nitrites and this is how we get most of our nitrites
Nitrites help open arteries and can lower blood pressure (4)
“Nitrate free” cured meats usually contain celery juice which provides an alternative source of nitrates
To ingest a fatal dose of nitrites a 60kg human would have to eat over 30kg of cured meat in one go (1)
The nitrate debate is intense. We don't have definitive answers and most of the research calls for further reasearch particularly using human subject instead of animals. In addition causal studies need to be conducted rather than associative studies which are often affected by other factors. Nitrates clearly have benefits and are also toxic in extremely large doses. As with all things moderation is recommended even if you believe they are harmless.
I have listed the articles I used to prepare this post below if you wish to read them. Please feel free to debate the topic further with myself but bear in mind I am not a scientist. If I have misinterpreted the articles please let me know. If you do have a strong opinion please have the decency to include your scientific references in the debate.
1. Nitrite in Meat – Richard J. Epley, Paul B. Addis and Joseph J. Warthesen, University of Minnesota 2012
2. Food sources of nitrates and nitrites: the physiologic context for potential health benefits – Hord NG, Tang Y, Bryan NS, American Journal of Clinical Nutrition 2009
3. Human safety controversies surrounding nitrate and nitrite in the diet – Jeffrey J. Sindelar, Andrew L. Milkowski, University of Wisconsin 2012
4. Nitrate in foods: harmful or healthy? – Martijn B Katan, American Journal of Clinical Nutrition 2009
5. When does nitrate become a risk for humans? – Powlson DS, Addiscott TM, Benjamin N, Cassman KG, de Kok TM, van Grinsven H, L'Hirondel JL, Avery AA, van Kessel C, Journal of Environmental Quality 2008
6. Consumption of cured meats and prospective risk of chronic obstructive pulmonary disease in women – Jiang R, Camargo CA Jr, Varraso R, Paik DC, Willet WC, Barr RG, American Journal of Clinical Nutrition 2008
7. Cured meat consumption, lung function and chronic obstructive pulmonary disease among United States adults – Jiang R, Paik DC, Hankinson JL, Barr RG, American Journal of Respiratory Critical Care 2007
8. Prospective study of cured meats consumption and risk of chronic obstructive pulmonary disease in men – Vaqrraso R, Jiang R, Barr RG, Willett WC, Camargo CA Jr, American Journal of Epidemiology 2007