What Are Nitrates?
Potassium nitrate (often shortened to "nitrate") has been used to preserve food since the Middle Ages. In the old days they called it saltpeter (Latin for "rock salt"). In the early 20th century, scientists discovered what made saltpeter an effective preservative, and it no longer became necessary to use saltpeter - a pure dose of nitrate was now known to do the trick.
Nitrates work by causing a reaction in the meat that creates nitric oxide. This, in turn, binds to the iron atom in the myoglobin in the meat (the stuff that makes raw meat look bloody even though all the blood has been drained off). This keeps the iron from causing the fat in the meat to oxidize - and it happens to cause cured meat to look pinkish-red. In addition, nitrates give meat a sharper taste and keeps certain pathogens, like botulism, at bay.
Why Nitrates in Meat Aren't Scary
Nitrates, my friends, are everywhere. You can't avoid them. Your very saliva makes up "93% of the total daily ingestion of nitrate" in your diet (your saliva reacts with bacteria in your mouth, creating nitrates), and "foods account for a very small portion of the overall daily nitrite intake."
When it comes to food, you can't avoid nitrates even by eating vegetarian. Vegetables actually make up the largest part of our dietary intake of nitrates (about 87%). The highest offenders are the very same foods health experts tell us to eat more of: spinach, beets, broccoli, leeks, radishes, lettuce, celery, cabbage, fennel, and cucumbers. In fact, one serving of arugula has more nitrates than 467 hot dogs.*
"One serving of arugula has more nitrates than 467 hot dogs."
Are Nitrate-Free Foods Really Free From Nitrates?
Read the label. It usually says something like "No nitrates added." The food itself may naturally have nitrates - and the manufacturers of the food probably have substituted pure nitrate with celery powder or celery juice. Since celery is high in nitrates, food made this way certainly isn't nitrate free.
As an example, a recent look at hot dogs found that "natural hot dogs had anywhere from one-half to 10 times the amount of nitrite than conventional hot dogs contained. Natural bacon had from about a third as much nitrite as a conventional brand to more than twice as much."
So Why Are Nitrates Supposedly Bad?
In huge amounts, nitrates are toxic. But to get enough nitrates to poison you, you'd need to eat thousands of hotdogs in one day.
In 1971, one study concluded that nitrate-preserved meats could cause cancer - "only under special conditions amines are present, nitrite is available to react, near neutral pH is found, and product temperatures reach greater than 130°C, such as during the frying of bacon." In reaction to the study, new laws were passed, lowering the amount of nitrates allowed in foods. Today, ascordbic acid (vitamin C) is used to inhibit the chemical reaction that could lead to nitrosamines. For bacon, regulations are tighter, and inhibitors for preventing nitrosamines during frying must be present. This resulted in an 80% reduction in nitrate levels - and since the 1980s, every decent scientific study (at least 80 of them) has found no link between nitrates in food and cancer.
So Are Nitrates GOOD?
Maybe. They do keep dangerous bacteria out of our food - and scientists are now looking into the idea that nitrates are beneficial to humans' immune system - and maybe even our cardiovascular systems.
Does That Mean Preserved Meats are Healthy?
All this isn't to say we should gorge ourselves on cured meat. There are indications that preserved meats cooked at high temperatures may lead to higher levels of colon cancer, for example. And there is (very flimsy) evidence that nitrates may react with natural amines found in some foods, forming a carcinogen called nitrosamine in the stomach. But, despite what you may hear, nitrates are not to blame.
So while it's probably smart to limit your intake of cure meat, at least now you know not to waste your money on supposedly "nitrate free" foods that aren't really free from nitrates at all.