There is one main concern when curing and preserving meat, and that is botulism. While botulism is usually related to improper canning procedures, food-borne botulism also occurs in meats that have been improperly cured.
To prevent this, commercially preserved meats contain sodium nitrite (sometimes called “pink salt”), which acts both as a preservative and a color fixer. This is what gives store-bought bacon that bright red color.
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Sodium nitrite is toxic in high quantities, and has been linked to migraines in certain people.
Some organic “un-cured” bacon brands use celery juice in lieu of pink salt, but celery juice can often contain even more naturally-occurring sodium nitrite than the curing salt! This won’t help migraine sufferers much.
But the main concern with sodium nitrite (or even high levels of naturally-occurring nitrites from celery juice) is that when it is exposed to high heat in the presence of protein (like a piece of fried, nitrite-cured bacon), proteins in the meat bond with the sodium nitrite to produce toxic nitrosamines—and certain nitrosamines have been proven to be deadly carcinogens.
Basically, frying and eating nitrite-cured bacon presents the perfect scenario for nitrosamines to enter your system.
That sounds pretty bad, right?
Unfortunately, the sodium nitrite (or naturally-occurring nitrites from celery) is necessary in a large industrial setting, where many different people, machines and industrial processes are involved in getting the meat from the feedlot to the store, free of botulism and other harmful bacteria.
But the home cook can much better control the variables and handling procedures, and can get those assurances without the addition of nitrites.