Study Compares Diabetes and Heart Risks of Processed and Unprocessed Meat
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But the study, published in Circulation, shows no such link for unprocessed red meat.
Eating one serving a day of processed meat -- or the equivalent of a single hot dog or two slices of salami -- was associated with a 42% increased risk for heart disease and a 19% increased risk for diabetes in the study, conducted by researchers from the Harvard School of Public Health.
Eating unprocessed beef, pork, or lamb was not linked to a higher risk for heart disease and diabetes.
The study is the largest research review ever to attempt to tease out the health impact of eating processed vs. unprocessed red meat.
The finding that all red meats are not equal when it comes to heart and metabolic disease risk has important implications for public health, says study researcher Renata Micha, PhD.
But that doesn't mean it's OK to eat steak for dinner every night if you cut way back on bacon at breakfast and hot dogs or deli meats at lunch.
"People should limit their consumption of processed meats," Micha says. "Eating up to one serving a week would not be associated with much risk. And this study should not be taken as license to eat unlimited amounts of unprocessed red meat."
Hot Dogs and Heart Risk
Micha and colleagues included 20 studies involving more than 1.2 million people in their analysis.
For the purposes of the study, red meat was defined as any unprocessed beef, lamb, or pork food.
Processed meat was defined as any meat preserved by smoking, curing, or salting, or any meat containing chemical preservatives such as nitrates.
Even after taking into account established risk factors for heart disease and diabetes, eating processed meat was associated with an increased risk for both.
Processed and unprocessed meats contained similar amounts of fat and cholesterol, but processed meats contained, on average, about four times more sodium and 50% more nitrate preservatives than unprocessed meats, the researchers note.
Salt consumption is a strongly linked to high blood pressure, which is a major risk factor for heart disease, according to the American Heart Association (AHA).
"The major difference in heavily processed and less processed meat is sodium and chemical preservatives," AHA spokesman Robert Eckel, MD, tells WebMD. "We have tended to blame the saturated fat in red meat for heart disease, but this study suggests it may not be that simple."
The study was funded by the Bill & Melinda Gates Foundation/World Health Organization Global Burden of Disease initiative along with the National Institutes of Health and the Searle Scholars Program.
Cancer Risk Not Studied
Micha says it is clear that future research on red meat and health should separate processed and unprocessed meats.
The role of processed vs. unprocessed red meat in other diseases, such as cancer, also remains to be determined.
Eating red meat and processed meat have been implicated in colorectal cancer, for example. But like the heart studies, most of this research has considered the two types of meat together.
Eckel says more research is needed to better understand the separate impact of processed and minimally processed red meat consumption on health.
He is a professor of medicine at the University of Colorado, Denver.
"This study is certainly interesting, but the findings are hypothesis generating," he says. "They are not definitive."
SOURCES: Micha, R. Circulation, May 17, 2010; online edition.
Renata Micha, PhD, RN, research fellow, department of epidemiology, Harvard School of Public Health, Boston.
Robert Eckel, MD, professor of medicine, University of Colorado Denver; spokesman, American Heart Association.
News release, Harvard School of Public Health.
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