Researchers at the Harvard School of Public Health have found that eating processed red meat—bacon, sausage or processed deli meats—was associated with a 42% higher risk of heart disease and 19% higher risk of type 2 diabetes.

The researchers did not find a higher risk of heart disease or diabetes among individuals who ate unprocessed red meat: beef, pork, or lamb.

“Although most dietary guidelines recommend reducing meat consumption, prior individual studies have shown mixed results for relationships between meat consumption and cardiovascular diseases and diabetes,” says Epidemiology Fellow Renata Micha, whose research was published Monday in the online edition of Circulation. “Most prior studies also did not separately consider the health effects of eating unprocessed red versus processed meats.”

The researchers defined unprocessed red meat as any unprocessed beef, lamb or pork; poultry was excluded. 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/luncheon meats. Vegetable or seafood protein sources were not evaluated.

Study Findings

The results showed that, on average, each 50-g (1.8-oz.) daily serving of processed meat (about 1–2 slices of deli meats or 1 hot dog) was associated with a 42% higher risk of developing heart disease and a 19% higher risk of developing diabetes.

“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,” Micha says. “In contrast, processed meats contained, on average, 4 times more sodium and 50% more nitrate preservatives. 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.”

Dietary sodium (salt) is known to increase blood pressure—a strong risk factor for heart disease. In animal experiments, nitrate preservatives can promote atherosclerosis and reduce glucose tolerance, effects that could increase heart disease and diabetes risks.

Looking Toward the Future

Given the differences in health risks seen with eating processed versus unprocessed red meats, the findings suggest these types of meats should be studied separately in future research for health effects, including cancer, the authors say. For example, higher intake of total meat and processed meat has been associated with a higher risk of colorectal cancer, but unprocessed red meat has not been separately evaluated. They also say more research is needed on which factors (especially salt and other preservatives) in meats are most important for health effects.

Current efforts to update the federal Dietary Guidelines for Americans, which are often a reference for other countries around the world, make these findings particularly timely, the researchers say. They recommend that dietary and policy efforts should especially focus on reducing intake of processed meat.

“To lower risk of heart attacks and diabetes, people should consider which types of meats they are eating,” Micha says. “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.”