BOSTON—Eating processed meat, such as bacon, sausage or processed deli meats, is associated with a 42-percent higher risk of heart disease and a 19-percent higher risk of type 2 diabetes, according to a new study from the Harvard School of Public Health (HSPH) published in the journal Circulation. However, the researchers did not find any higher risk of heart disease or diabetes among individuals eating unprocessed red meat, such as from beef, pork or lamb.
Researchers systematically reviewed nearly 1,600 studies. Twenty relevant studies were identified, which included a total of 1,218,380 individuals from 10 countries on four continents (North America, Europe, Australia and Asia). The researchers defined unprocessed red meat as any unprocessed meat from beef, lamb or pork, excluding poultry. Processed meat was defined as any meat preserved by smoking, curing or salting, or with the addition of chemical preservatives; examples include bacon, salami, sausages, hot dogs or processed deli or luncheon meats. Vegetable or seafood protein sources were not evaluated in these studies.
The results showed, on average, each 50 gram (1.8 ounce) daily serving of processed meat (about one to two slices of deli meats or one hot dog) was associated with a 42-percent higher risk of developing heart disease and a 19-percent higher risk of developing diabetes. In contrast, eating unprocessed red meat was not associated with risk of developing heart disease or diabetes. Too few studies evaluated the relationship between eating meat and risk of stroke to enable the researchers to draw any conclusions.
“When we looked at average nutrients in unprocessed red and processed meats eaten in the United States, we found that they contained similar average amounts of saturated fat and cholesterol. In contrast, processed meats contained, on average, four times more sodium and 50-precent more nitrate preservatives,” said Renata Micha, a research fellow in the department of epidemiology at HSPH and lead author of the study. “This suggests that differences in salt and preservatives, rather than fats, might explain the higher risk of heart disease and diabetes seen with processed meats, but not with unprocessed red meats. “To lower risk of heart attacks and diabetes, people should consider which types of meats they are eating. Processed meats such as bacon, salami, sausages, hot dogs and processed deli meats may be the most important to avoid. Based on our findings, eating one serving per week or less would be associated with relatively small risk.”
However, the American Meat Institute Foundation (AMIF) issued a response to the study saying processed meat continues to be a healthy part of a balanced diet and that 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.
AMIF President James H. Hodges noted that this is an epidemiological study, which by itself is not sufficient to establish cause and effect. Rather, this type of study allows researchers to identify associations that may merit further study. Even the authors of the study state in the paper that “Associations of processed meat consumption with diabetes mellitus or CHD 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. 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,” Hodges said. “This study did not achieve the standard threshold that would generate concern. “At best, this hypothesis merits further study. It is certainly no reason for dietary changes.”
Click here to read the entire AMIF statement in response to the study.