Nitrosamines

Sporadic colorectal cancer can arise as a result of exposure to carcinogens. Compared to genetic or hereditary colorectal cancers, about 75% of all colorectal cancers occur sporadically. In such cases, cancerous growth does not occur because of preexisting mutations that are present in the cells from birth. Rather, these mutations occur as a result of external factors that cause damage to DNA.

Exposure to carcinogens may happen as part of occupational hazards, but more commonly occurs because of diet and lifestyle. In fact, it’s estimated that diet contributes to about 80% of colorectal cancer cases. Nitrosamines, sometimes written as N-nitrosamines, are carcinogens that are commonly used as preservatives in processed meats. The question is, how do nitrosamines cause cancerous growth in the colon and rectum?

Nitrosamines are organic compounds that contain alkyl and an aryl group with the following nitrogen and oxygen group: N–N=O.

Nitrosamines are commonly used as food preservatives, particularly in processed meats such as bacon, ham and sausages. However, they can also be found in other consumer products such as alcoholic beverages and cosmetics as well as tobacco smoke. Some drugs, such as those used to treat diabetes, high blood pressure, heartburn and acid reflux may also contain nitrosamines. Nitrosamines may also contaminate water sources through fertilizers that seep into nearby water bodies.

Nitrosamine can also be formed in the body such as the stomach. Sodium nitrite and sodium nitrate, both of which are food additives used when curing meat, are precursors of nitrosamine. These compounds may combine with amines in acidic conditions, such as in the stomach, to form nitrosamines.

While low concentrations of nitrosamines are generally considered safe, high levels of nitrosamines in the body have been found to increase the risk of several cancers including colorectal cancer.

Nitrosamines by themselves are not carcinogenic; it is when they are metabolized that they exert carcinogenic properties. The metabolic pathway involves cytochrome P450 enzymes that convert nitrosamines into highly reactive compounds. These intermediates can then alkylate DNA, forming DNA adducts, and induce mutations, ultimately contributing to the development of cancer.

Additionally, nitrosamines can also lead to the generation of reactive oxygen species (ROS) during metabolism. ROS can cause oxidative stress, damaging cellular components such as DNA, proteins, and lipids. This oxidative damage can further contribute to the initiation and progression of carcinogenesis.

While some nitrosamine sources such as contaminated water and drugs are difficult to avoid, those found in diet and lifestyle related products are more easily avoided. Reducing consumption of processed and cured meats and alcoholic beverages are just some of the ways to avoid ingesting nitrosamines and their precursors.