The Scare: “Think Twice Before You Bring Home the Bacon.” (40) Headlines like this one from NBC5.com warn consumers of a supposed link between bacon consumption and bladder cancer. Nitrosamines, which are suspected bladder carcinogens, or their precursors, are found in certain meat items. Meats contain amines. Nitrosamines form when sodium nitrite, an added preservative and a source of nitrosating agents, reacts with the amines present in the meat. Of all the cured meats, bacon has received the most attention. It often contains detectable levels of nitrosamines, principally nitrosopyrrolidine and, to a lesser extent, dimethylnitrosamine. The very high cooking temperatures used to fry bacon are conducive to nitrosamine formation. The removal of sodium nitrite as a food additive was considered in the late 1970s after extensive attention was focused on the issue of nitrosamines in cured meats. (42) A study published in the American Journal of Nutrition (43) in 2006 claimed to show a link between the consumption of bacon and skinless chicken and an increased risk of bladder cancer.
Origin of the Scare: In November, the American Journal of Nutrition published a study claiming that consuming five or more servings of bacon a week was associated with an increased risk of bladder cancer. The report analyzed the effects of meat consumption on two cohorts of men and women. The analysis showed that men and women with a high intake of bacon (five or more servings a week) had an elevated risk of bladder cancer compared with those who never ate bacon. The study notes that these results are not statistically significant. The authors also noted a positive association between intake of skinless chicken, but not for chicken with skin or for other meats, including hotdogs, processed meats, and hamburgers. The authors also note that other studies similar to theirs would need to be conducted to confirm the findings.
Media Coverage: Despite the fact that the results of this study were shown to be statistically insignificant, various newspapers picked it up with headlines such as “Bacon, Bad; Chicken Skin, Good,” “Think Twice Before You Bring Home the Bacon,” and “Bacon Tied to Bladder Cancer.” Reuters (44) reported that eating too much bacon could be hazardous to a person’s health because of the presence of nitrosamines, “which are known to cause bladder cancer.” The story was also reported on BBC News in the United Kingdom. (45) This report was fairly balanced, noting that the research was far from definitive. It also mentioned that the study shows that those who ate the most bacon were also more likely to smoke and take in more fat and fewer vitamins, and less likely to exercise, all risk factors for cancer.
The Bottom Line: The results from the study of the American Journal of Clinical Nutrition should not concern anyone who occasionally enjoys bacon and skinless chicken. First of all, the results were not statistically significant. Secondly, this is only one study, and the first of its kind, and therefore, it needs to be replicated in future studies in order to prove a link between bacon and skinless chicken and bladder cancer.
The other factor to consider is the labeling of nitrosamines as carcinogens. Most suspected carcinogens are tested in high-dose rodent studies. There are major biological and physiological differences between rats or mice and humans that prevent rodent studies from accurately predicting cancer risk in humans. Additionally, these studies expose the animal to far higher doses of a chemical than a human would normally encounter.
Sodium nitrite is added to meat as a preservative, especially in preventing the growth of the bacterium that causes botulism. When sodium nitrite is added to meat, it combines with the amines already present in the meat to form nitrosamines, the suspected carcinogens. Removing sodium nitrite from meat would prevent nitrosamine formation, but it might also increase the risk of botulism poisoning. (46) In this case, the real risk of botulism poisoning outweighs the unproven risk of bladder cancer.
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