The Science Behind the Sandwich: Exploring Processed Meats

“Hello, can I please get a turkey footlong on Italian Herb and cheese bread? Can I also add some bacon on that as well?” 

Although this iconic Subway order may be difficult to resist, the processed meat in the sandwich can degrade health in many ways that consumers do not realize. Being one of the few foods classified as a Group 1 carcinogen by the International Agency for Research on Cancer, it is placed in the same category as the effects of smoking tobacco, alcohol use, asbestos exposure, and radiation exposure (American Cancer Society, n.d.). Although the effects of processed meats are not necessarily equivalent to these carcinogens, this classification provides evidence of the link between processed meat consumption and cancer in humans.

Chemical additives and processing methods are used to preserve shelf life, but they are the very reason that these meats have become a growing health concern. Nitrite (NO2)^– is the most common additive in processed meats (either added directly or formed from nitrate), as it is responsible for preventing any bacterial growth that forms (Zhang et al. 2023). Additionally, (NO2)^– is responsible for inducing a chemical reaction that produces the pink pigment on deli meats, as opposed to red pigment that it naturally has (Shakil et al. 2022). This chemical change begins with the conversion to nitric oxide during the curing process and further binds to the iron in myoglobin. This produces a pink compound, called nitrosomyoglobin, that is active for the remainder of the meat’s shelf life. When consumed, the negative effects of (NO2)^– is demonstrated because of its chemical reactivity within our body. In the stomach, where the pH levels are low and highly acidic, (NO2)^– reacts with the acid and promotes endogenous nitrosation with amines and amides from proteins (Ward 2009). This process produces various N-nitroso compounds, including a carcinogenic subgroup known as N-nitrosamines (Figure 1). 

This group of compounds are dangerous since they are metabolized into reactive intermediates that form DNA adducts, which are abnormal chemical attachments to DNA (Li and Hecht 2022). These DNA attachments can introduce mutations that interfere with cell growth and division since the DNA is responsible for carrying cellular instructions. If these mutations involve cell-cycle control or DNA repair processes, the cell may stop responding to normal growth signals (Ward 2009). Therefore, cells may divide uncontrollably and lead to cancer. 

This is especially concerning since (NO2)^– is advertised as improving the quality of the product, but its chemical behaviour clearly leads to worse effects at the cellular level (Karwowska and Kononiuk 2020). Although completely removing processed meats from one’s diet is most ideal, scientists have begun to explore alternatives to lower reliance on (NO2)^–. For example, using plant-derived antioxidants is an emerging approach in preserving meats and is a much safer option (Shakil et al. 2022). 

So next time you are at Subway, think twice about getting that nitrite-infused turkey sandwich!

References

American Cancer Society. n.d. “Known and Probable Human Carcinogens.” https://www.cancer.org/cancer/risk-prevention/understanding-cancer-risk/known-and-probable-human-carcinogens.html. 

Karwowska, Małgorzata, and Anna Kononiuk. 2020. “Nitrates/Nitrites in Food-Risk for Nitrosative Stress and Benefits.” Antioxidants (Basel, Switzerland) 9 (3): 241. https://doi.org/10.3390/antiox9030241. 

Li, Yupeng, and Stephen S. Hecht. 2022. “Metabolic Activation and DNA Interactions of Carcinogenic N-Nitrosamines to Which Humans Are Commonly Exposed.” International Journal of Molecular Sciences 23 (9): 4559. https://doi.org/10.3390/ijms23094559. 

Shakil, Mynul Hasan, Anuva Talukder Trisha, Mizanur Rahman, et al. 2022. “Nitrites in Cured Meats, Health Risk Issues, Alternatives to Nitrites: A Review.” Foods (Basel, Switzerland) 11 (21): 3355. https://doi.org/10.3390/foods11213355. 

Ward, Mary H. 2009. “Too Much of a Good Thing? Nitrate from Nitrogen Fertilizers and Cancer.” Reviews on Environmental Health 24 (4): 357–63. https://doi.org/10.1515/reveh.2009.24.4.357. 

Zhang, Yin, Yingjie Zhang, Jianlin Jia, et al. 2023. “Nitrite and Nitrate in Meat Processing: Functions and Alternatives.” Current Research in Food Science 6 (February): 100470. https://doi.org/10.1016/j.crfs.2023.100470.