Nitrates, nitrites, and nitrosamines

There seems to be a lot of confusion about the issues of nitrates, nitrites, and nitrosamines, so much that some people—including book authors and doctors—are declaring that they are entirely benign and not an issue for health. Let’s try and clear up the confusion.

Much of the confusion stems from the fact that nitrates and nitrites occur in many foods, including vegetables and fruit. Upon ingestion, nitrates and nitrites are converted to nitric oxide, the master vasodilator (artery relaxing agent) that thereby contributes to healthy arteries and blood pressure. So there is nothing intrinsically wrong with nitrates or nitrites that are ingested via food.

Ah, but here’s the problem: When heated, nitrites react with the NH3 (amine) group on proteins and yield nitrosamines and other N-nitroso compounds such as N-nitrosodimethylamine, NDMA. We have plenty of experimental evidence that the 20+ known nitrosamines, including those from cigarettes, are potent carcinogens. There is also emerging evidence that N-nitroso compounds are associated with Alzheimer’s dementia.

The human evidence linking N-nitroso compounds with cancer is observational and epidemiological. While I criticize over-reliance on observational data that too often leads to mistaken conclusions in nutrition, in this area we will never have clinical trial data, as it would be unethical. To prove whether or not the carcinogenic observations made via observational epidemiological studies hold true in a clinical trial, we would have to have a group of people ingest nitrosamines and another group not ingest nitrosamines and see who gets more cancers—obviously, this will never be done. So, in this instance, it is unreasonable to demand that we generate clinical trial confirmation of the observational data, although that is what we do in the area of nutritional epidemiology. Can’t do that in cancer. But this is the same level of evidence that we have for glyphosate, radon, and asbestos as carcinogens.

So we are left with plenty of experimental data and weak observational data that suggest that sodium nitrites that react with proteins upon heating may be carcinogenic. That’s as solid as the argument gets—but it’s good enough for me.

It means that, as I discussed in the Wheat Belly and Undoctored books, we steer clear of meats containing sodium nitrite to avoid inducing creation of N-nitroso compounds upon heating.

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