Nitrites, chemicals used to process hot dogs, smoked hams, and sausages, have been under fire in recent years from epidemiologists who had found a link between cured meats and certain childhood cancers. However, an interdisciplinary task force of scientists concluded in a recently issued report that there is virtually no scientific rationale for this conclusion.
“A critical review of the available information on smoked food sold in the United States indicates that these foods are safe,” said Michael Pariza, director of the Food Research Institute at the University of Wisconsin-Madison and chair of the Council for Agricultural Science and Technology task force that issued the report.
The task force, including a world-renowned epidemiologist and several scientists from the UW-Madison, cited limitations in the epidemiological studies and chance for confounding the results.
For instance, in a study that showed hot dogs were linked to childhood leukemia, bacon and lunch meat did not show the same relationship even though they have similar levels of residual nitrites. This led the scientists to conclude that there may be other factors causing the relationship, such as the levels of fat, folate, and fruits and vegetables in the children”s diets.
Methodology also limited the epidemiological studies. The studies had asked participants to recall their dietary habits. According to Pariza, parents of children who have cancer may remember or report consumption differently due to the experience of cancer in their children. A much stronger study would have parents record their children”s diet for a period of time and report the incidence of cancer in those children at a later time.
“Most of the epidemiologists have backed away from the findings of these studies,” Pariza said. “They [the findings] could even be a statistical fluke due to the rarity of the cancer.”
Curing meat by smoking or salting has been a preservation method for centuries. At the end of the last century, scientists discovered that nitrite was a crucial preservative in the process. Nitrite not only prevents spoilage, but also reacts with the meat pigment myoglobin, giving cured meat such as ham its distinctive pink color. More importantly, nitrite inhibits microorganisms, such as those that cause botulism, if they are present.
However, in the 1970s, consumer groups began to question the safety of nitrite-cured meats. Scientists had discovered that a chemical reaction between nitrite and certain components of proteins, called amines, formed chemicals that could cause cancer in lab animals.
“Nitrites can react with amines to form nitrosamines, which are known cancer causers,” said Robert Cassens, emeritus professor of animal science at the UW-Madison who has extensively studied nitrites in cured meats.
Even so, there have been no nitrosamines found in cured meats through analytical chemistry techniques, said Cassens. Hypothetically, a small risk of cancer might come from nitrites remaining in meat that is eaten by people who may already have amines in their stomachs, Cassens said. Certain medicines contain amines, for example.
Unfortunately there are no reasonable substitutes for nitrite. “The cancer risk is minimized by minimizing intact nitrites left in the meat,” Cassens said.
The allowable amount of nitrite in cured meat is 1/4 ounce per 100 pounds of meat, a very low level. Also, since the 1970s, there has been an 80 percent reduction of residual nitrite in cured meats, so only 10 to 20 percent of the nitrite remains. At the same time, processors began adding vitamins C and E to meats to speed up the curing process. These vitamins have been found to inhibit the formation of nitrosamines in the stomach in human studies, Cassens said.
Due to these changes, the American Cancer Society in 1996 said that “nitrites in food are not a significant cause of cancer in Americans.” In fact, nitrites and nitrates, which can be converted to nitrites in the digestive system, are commonly present in many vegetables, said Pariza.
For example, according to Pariza, someone eating a bacon, lettuce and tomato sandwich for lunch will show an increase in blood nitrite levels. Some of that is due to the bacon, however a larger amount is due to the lettuce and the tomato. Nevertheless, research has shown that the benefits of eating vegetables far outweigh the concerns about nitrites in the diet. It is also important to remember that nitrites, alone, do not cause cancer.
For a copy of the task force”s report send $3 to CAST, 4420 West Lincoln Way, Ames, IA 50014-3447, or visit the CAST web site at http://www.netins.net/showcase/cast The title of the eight-page report is Examination of Dietary Recommendations for Salt-Cured, Smoked, and Nitrite-Preserved Foods.