Sodium nitrate and sodium nitrite, two common preservatives used in foods, are often used interchangeably. So it comes as no surprise that many people don't know the difference between the two. What it comes down to is one oxygen atom — sodium nitrite has two oxygen atoms and one nitrogen atom. Sodium nitrate has one more oxygen atom.
Either kind of preservative can be added to meat to keep bacteria from growing on it, but once we consume them, nitrates are converted to nitrites in our digestive system. And what's the harm in nitrites, you might ask?
In the human body, nitrites form nitrosamines, which have been associated with various cancers. In 2005, a study at the University of Hawaii linked consumption of processed meats to a 67 percent increase in the risk for pancreatic cancer. Yet another more recent study links eating too much processed meats to heart disease and diabetes. Interestingly enough, the researchers did not find that eating unprocessed meat at the same rate led to nearly the same risk. What's the difference in the meats that contain similar amounts of saturated fat and cholesterol? The processed meats had four times the amount of sodium and 50 percent more sodium nitrite.
There are hot dog brands that claim that no nitrates have been added to the meat. A closer look at the label reveals that most of these hot dogs actually contain celery powder, which contains nitrates that occur naturally in said vegetable. There are, in fact, many vegetables that contain nitrates — beets, for example, as well as a variety of leafy greens. So are these nitrates any better for us than the ones put in artificially?
A 2008 report by the European Food Safety Authority states that there is no reported risk of eating high amounts of nitrates in vegetables. As a matter of fact, the benefits of eating those vegetables far outweigh the risks. The nitrates in those vegetables don't have the same effect on our bodies as the ones that are artificially added to meats because these veggies also contain vitamins C and D, which inhibit the formation of those N-nitroso compounds. On the other hand, some data suggests that very high levels of nitrate consumption can cause gastric problems.
So what to do when it comes to nitrate-containing food? Moderation is the key.
I also want to mention the rare but dangerous scenario of excess nitrates in food or water fed to infants, particularly infants who are younger than 3 months old. Excess nitrates can lead to nitrate poisoning, known as "blue baby syndrome," where the nitrates in the baby's blood build up so much that it prevents the hemoglobin from carrying oxygen to where it needs to go.
The American Academy of Pediatrics recommends that if you feed your newborn well water (as is the case in some municipalities if you formula feed and mix your formula with water from the tap), you should have your water tested for nitrate content, since the greatest risk of nitrate poisoning occurs in infants fed well water contaminated with high nitrate levels. (Nitrate poisoning is also possible when babies younger than 3 months are fed homemade baby food from nitrate-containing vegetables, but that's less of a problem since you really shouldn't be feeding a baby that young anything but formula or breast milk anyway.) The nitrate concentration of the water should be less than 10 parts per million.