Guest post by Dr. Jeff Sindelar and Dr. Andrew Milkowski,  University of Wisconsin

Nitrate and Nitrite have been used for millennia as part of systems to preserve meat so that it could be safely stored for consumption to avoid waste and provide wholesome meat protein during times of need.  Mankind quickly discovered that cured meats were largely free of the danger of botulism poisoning when eating preserved meats.  As scientific knowledge developed, we became more sophisticated in how to use these ingredients and this classification of pink colored cured meat products enjoyed by people in all cultures around the world became established.

A Historical Perspective

In the 1950s and 1960s, as inquiry into causes of cancer expanded to a molecular level, nitrosamines were discovered as carcinogens and scientists realized that under some conditions of food preparation, namely high heat, they could be formed in small quantities in cured meats.  This led to a revaluation of the safety of nitrite, and it was almost banned as an ingredient in the late 1970s.

After an intense review of the risk, the issues were resolved in the early 1980s. Curing methods were changed to drastically reduce nitrate and nitrite usage as well as introduce use of ingredients such as ascorbic acid (vitamin C) to inhibit nitrosamine formation. Stringent US regulatory limits were also put into place, particularly for bacon which is fried at high temperatures.  Those regulations have remained intact for over 30 years and continue to serve society well in dealing with this low risk.

New Science Emerges

As our basic knowledge of nitrite and nitrite chemistry has increased, we can now be assured that nitrite is not universally bad, but rather an essential part of human physiology.  In the 1980s another nitrogen oxide, nitric oxide was discovered to be synthesized from the amino acid arginine in the human body during normal metabolism.  It controls or influences a host of essential body functions such as immune response, blood pressure, memory and wound healing.  Many of the physiological effects of nitric oxide are exerted through nitrite and nitrate.  Nitrite itself has been shown to be very important for controlling blood flow in the heart.  We also appreciate how the body recirculates nitrate via secretion in saliva and conversion to nitrite by normal bacterial found in the mouth.

Another thing we have learned to appreciate more fully is the role that nitrite has in protecting against food borne pathogenic bacteria.  The fact that nitrite provides us safety from botulism is well established.  It also is a key part of the food safety hurdles designed into processed meats to deal with risk from another pathogen, Listeria monocytogenes, which we did not really appreciate 30 years ago.  Furthermore, the production of nitrite in the saliva has been shown to enhance the ability of stomach acids to kill bacteria that we inherently swallow.  In this sense, nitrite can be considered part of our innate immune system that protects against infection.

Thus we need to rethink the paradigm that nitrate and nitrite in cured meats should be always considered with suspicion.  Most human exposure to these two compounds comes from metabolism (by arginine) and physiology, consumption of vegetables that are commonly high in nitrate (lettuce, celery, spinach, beets) and the recirculation pathway in the saliva. Overall, nitrate and nitrite from cured meats realistically provide less than a 10 percent of our daily exposure and it makes little sense to consider this hazardous in light of the much larger amounts that are consumed from vegetables or naturally generated in our bodies.

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