Consumption of processed red meats, which include bacon, sausage and deli meats, was found to increase a person’s risk for heart disease and diabetes. The new findings out of the Harvard School of Public Health lend support to the idea that in order to eat a healthy diet, a person might want to avoid these types of foods. The study did not find a the same link with eating unprocessed red meat, whether it be from beef, pork, or lamb.

The study, published in the journal Circulation, is the first systematic review of the global data that is available the examines the relationship between eating processed or unprocessed meats and chronic health conditions. Previous research supports a reduction in eating red meats, but the different health consequence between processed and unprocessed meats was never completely clarified.

In order to arrive at their findings, epidemiologists examined the data of over 1,600 studies. They then focused on 20 of them that encompassed over 1.2 million people spanning 10 countries in 4 continents, including North America, Europe, and Asia. Processing was defined as any meat that underwent smoking, salting, or treatment with a chemical preservative. Meats included in this group were bacon, salami, sausage, hot dogs, and deli meats. The researchers did not include vegetables or seafood in their analysis.

According to the findings, for every 50 grams of processed meat that are consumed each day, which is the equivalent of one to two slices of deli meat or one hot dog, the risk for heart disease increased by 42% and the risk for diabetes went up by 19%. Unprocessed red meats, on the other hand, were not associated with any risks for these conditions. Because of a lack of data, no conclusions regarding stroke risk could be made.

The authors stress that a causal relationship cannot be deduced from these observational studies. However, even after adjusting for other risk factors and important lifestyle considerations, processed red meats were still linked to a higher incidence of disease.

Interestingly, further analysis revealed the saturated fat and cholesterol content of the two types of meat were similar, but processed meats contained four times more sodium and 50% more nitrate preservatives. This may suggest that the salt and preservatives, as opposed to just fat and cholesterol, may be the most significant contributing factor to health problems. This is especially true in light of the fact that excessive consumption of sodium is known to increase blood pressure, which in turn raises our risk for heart disease. Scientists have also determined that nitrate preservatives can increase the risk for atherosclerosis and diabetes in animal models.

While the review opens the door for further inquiry, especially in relation to other diseases, including cancer, the take home message is close to what we’ve been told for years: eat less processed meat. Along with this recommendation, we should strive to eat more fresh fruits and vegetables, as well as lean meats (fish and chicken), legumes, and whole grains.

If you have questions about your diet, talk to your doctor, and visit the website for My Pyramid for more information about healthy eating.