WHEN shopping for food, we mostly rely on visual cues. Meat processors and marketeers go to great lengths to ensure that their products have an appetizing, fresh-looking shade (pink or red), even after weeks of storage. The cheapest and quickest way to produce nice-looking bacon, ham or gammon is to use small quantities of three powerful chemical agents: potassium nitrate (E252), sodium nitrate (E251) or sodium nitrite (E250).

For years, scientists have denounced the impact on health of these additives. The carcinogenicity of nitro-processed meats doesn't come from nitrite itself nor nitrate itself: neither of these substances is directly carcinogenic. The cancer-causing agents are formed through the encounter of meat components with nitrate and nitrite derivates. The most famous are nitrosamines and nitrosamides. They are carcinogenic even at very low dose.

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In order to minimise nitrosamine/nitrosamide formation, producers add vitamin C. Unfortunately, the "vitamin C" trick does nothing to prevent the formation of another carcinogenic compound: nitrosyl-haem, which occurs from the junction of nitrite with haem (meat iron).

Processed meats are part of our common food heritage. They do not need to be carcinogenic. All over Europe, a select number of meat processors are disrupting the deadly status quo in order to produce great-tasting and safer processed meats. The most famous case is Parma ham which is produced without nitrate or nitrite.

In France, several large producers of Bayonne ham have recently switched back to the same natural, no-nitrate/no-nitrite technology. When no nitro-additive is used, the final product gets its beautiful red colour from a natural pigment.

In the eyes of many producers, this process has one serious disadvantage: it is slow, because the formation of the natural pigment requires an enzymatic transformation of the meat. The colour, taste, and self-preservation quality of the slowly matured ham will take approximately nine months to form.

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If, instead of that, you inject the ham with nitrate or nitrite, you get the same result in just 90 days. It requires much less work and less technical qualification. No doubt it saves money. But is it really worth it? Frankfurters or bacon can also be produced without nitro-additives.

Yet, the carcinogenic nitrate/nitrite version are still widely available in schools and hospitals all over Scotland. It seems rather absurd, to say the least: who can doubt that minimising exposure to carcinogenic agents is an absolute duty of Government? Removing nitro-meat from menus is now urgent, as there can be no justification to feeding cancer-promoting foods to hospital patients or to school kids.

Guillaume Coudray is the author of 'How Processed Meat Became a Poison' (2017)