WASHINGTON – Processed meat continues to be a healthy part of a balanced diet and nutrition decisions should be based on the total body of evidence – not on a study that stands in contrast to other research and to the U.S. Dietary Guidelines for Americans. So stated the American Meat Institute Foundation (A.M.I.F.) in responding to a recent study published in the journal Circulation.
This is an epidemiological study, which by itself is not sufficient to establish cause and effect, said James Hodges, A.M.I.F. president. This type of study allows researchers to identify associations that may merit further study. Authors of the study state in the paper that “Associations of processed meat consumption with diabetes mellitus or C.H.D. could relate to generally less healthy diet or lifestyle rather than causal effects of processed meats.”
“Too often, epidemiological findings are reported as ‘cased closed’ findings, as if a researcher has discovered the definitive cause of a disease or illness,” Mr. Hodges said. “But epidemiological studies look at a multitude of diet and lifestyle factors in specific volunteer human populations and use sophisticated statistical methods to try and tease out relationships or associations between these factors and certain forms of disease. This method of comparing relationships has many limitations, which are widely recognized by researchers in this field. More often than not, epidemiological studies, over time, provide more contradictions than conclusions.”
Epidemiological studies use “odds ratios” to estimate the strength of an association between the disease and the risk potential of a measured variable, such as a specific food or lifestyle choice, he also noted. An odds ratio of “1.0” means particular variable was statistically neutral in its effect. When the number falls below “1.0,” the finding suggests that variable may protect against a disease outcome. When the number is above “1.0,” a factor may need to be examined more closely related to its risk profile.
Although complicated statistical models are used to establish the "level of significance, a general rule of thumb within the field of epidemiology holds an odds ratio below “2.0” is not viewed as a strong relationship and may actually have occurred merely by chance. Epidemiological studies thought to have truly uncovered significant associations and cause for concern – like studies looking at tobacco and lung cancer – found odds ratios in the 10-25 range.
“This study did not achieve the standard threshold that would generate concern,” Mr. Hodges said. “At best, this hypothesis merits further study. It is certainly no reason for dietary changes.”
Although the authors speculate that sodium in processed meats may be problematic, there are many foods higher in sodium that are more commonly consumed, Mr. Hodges pointed out. In a ham sandwich, bread and condiments contribute more sodium than the ham.
Suggesting nitrite in cured meats is a risk factor ignores the major sources of nitrite in the diet. Less than 5% of human nitrite intake is from cured meats. Ninety-three percent is from leafy green and root vegetables like spinach, beets, celery and lettuce, which contain nitrate that is converted to nitrite in human saliva and swallowed.
The body makes nitrite as a critical signaling compound of the normal human nitrogen cycle. This important natural human pathway has been documented to have many health promoting benefits including wound healing, regulating blood pressure, preventing preeclampsia in pregnant women and it performs many other essential functions. Furthermore, nitrite in cured meats prevents the outgrowth of Clostridium botulinum, which causes botulism.
While the researchers speculated nitrite in some cured processed meats could be problematic, the National Institutes of Health National Heart, Lung and Blood Institute (N.H.L.B.I.) is researching nitrite’s health benefits.
Dr. Mark Gladwin of N.H.L.B.I., whose lab uncovered nitrite’s value as a medical treatment for various circulatory conditions, told reporters in September 2005, “The idea it’s bad for you has not played out…We think we stumbled into an innate protection mechanism.” Mr. Gladwin said N.I.H. believes so strongly in its promise that it is seeking a pharmaceutical company to help develop it as a therapy.
“The body of evidence clearly demonstrates that processed meat is a healthy part of a balanced diet,” Mr. Hodges concluded.