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Nitrates, Nitrites and Nitrosamine
As seen on BCTV Noon News
Nitrosamines are potent carcinogens which can induce tumour growth in humans. They are formed through the reduction of nitrates to nitrites by dietary substrates, such as amines and amides, via a conversion known as N-nitrosation. This can occur in the saliva as well as the stomach, colon and bladder. Nitrites can be found in a number of foods, but are found predominantly in the processes of pickling, salting and curing. A number of studies have found that nitrosamines play a role in the pathogenesis of gastric and colon cancers. However, researchers recognize that there are many confounding factors involved such as other dietary or lifestyle habits, all of which may have a contribution related to the disease development. Below is a list of foods that contain nitrites/nitrates and their associated risk with gastrointestinal (GI) cancers.
- Vegetables: While vegetables have been found to be a main dietary source of nitrates, no associated risk of GI cancers has not been found. Vegetables are excellent sources of a variety of antioxidants, such as vitamin C and phytochemicals, which can slow down or block the conversion of nitrites to nitrosamines and effectively protect against cancer risk. Remember to fill your plate with nutrient dense fruits and vegetables at every meal, aiming for at least 5 servings a day! Eating fruits and vegetables with foods that contain nitrites will provide protection from their conversion to nitrosamines.
- Beer: It is hard to believe, but beer is actually a large source of dietary nitrosamines in North America. While beer has been associated with colorectal cancer risk, some beer companies have fortunately reduced the concentrations of nitrosamines as a result of their changed method of drying malt. However, beer should still be consumed in moderation.
- Cured meat products: That characteristic pink colour of the luncheon meats and sausages that many use for sandwich protein fillers or breakfasts respectively, have been known for their contribution to nitrosamine intake in many countries. In fact, many studies have found an increased colorectal, rectum and stomach cancer risk associated with high consumption of these processed meats, in particular salami, sausages, bologna, ham and bacon. Remember that variety in the diet is a key part of healthy living. Try to consume a wide range of different protein sources such as beans and tofu, peanut butter, fish, sliced fresh meats and cheeses. Better choices at the deli counter include oven roasted turkey and chicken which contain less nitrates.
- Salted fish: Frequent consumption of dried, smoked and salted fish has been found to be associated with colon and rectal cancers in a number of populations. However, no association with cancer has been found for the consumption of fresh unsalted fish, which did not contribute an appreciable amount of nitrosamines. Fresh fish has many nutritional benefits such as omega 3 fatty acids and is a great source of protein. Try to consume fresh fish in place of salted, smoked or dried fish more frequently.
The Bottom Line: A high nitrosamines intake has been linked to GI cancers, especially from cured meats, sausages and salted fish. Try to consume these foods in moderation, limiting deli meats to twice a week. Try to eat vegetables and fruits which are high in antioxidants, vitamin C and phytochemicals and have shown significant protection against cancer by blocking nitrosamine formation. Eat a variety of fruits and vegetables every day, and make them the largest portion of your plate! Aim for 5-10 servings per day.
Watch for the Eating for Energy segment every Tuesday on BCTV’s Noon News Hour!