Nitrates, naturally occurring compounds consisting of oxygen and nitrogen, are found in soil, water and a number of foods, such as vegetables. Nitrates themselves are not harmful. Cured meats may contain nitrates as preservatives. Once eaten, nitrates convert to nitrite. Nitrites can combine with amines, products of protein breakdown in meats, to form nitrosamines, potentially harmful substances. Ascorbic acid must be added to foods in the United States that use sodium nitrate, because it decreases nitrosamine formation.
Increased Cancer Risk
Nitrosamines that form in cured meats have caused cancer in animals in a number of studies, according to the Agency for Toxic Substances and Disease Registry. Cancers most commonly associated with nitrosamines include bladder, esophageal, nasopharynx and prostate cancers as well as non-Hodgkins lymphoma, the organization states. Nitrosamines may also increase the risk of developing colorectal and stomach cancer. Cancers of the central nervous system, heart, thyroid and kidney have also been produced in animal studies, the International Programme on Chemical Safety reports.
Frying bacon well-done creates more nitrosamines, most often nitrosopyrrolidine or, less commonly, dimethylnitrosamine, than not cooking it as well or microwaving it. Fat dripping on hot coals when nitrate-containing meats are broiled can produce benzopyrene, a carcinogenic substance that can be carried on the smoke and deposited back on the meat. While numerous animal studies indicate that nitrosamines have carcinogenic properties, human studies are needed.
In animal studies, administration of several types of known carcinogenic nitrosamines in animals produced genetic mutations and chromosomal abnormalities, according to the IPCS. Whether these same changes affect humans has not been adequately studied.
In animal studies, some types of nitrosamines have caused birth defects as well as increased pregnancy loss, the IPCS reports. Studies to determine the effects of humans are lacking.