So what is it in red meat that might make it unhealthy?
No one is sure, exactly, but the authors of the Harvard study mention a few possible culprits in theirpaper in the Archives of Internal Medicine.
First, eating red meat has been linked to the incidence of heart disease. The saturated fat and cholesterol in beef, pork and lamb are believed to play a role in the risk of coronary heart disease. The type of iron found in red meat, known as heme iron, has also been linked to heart attacks and fatal heart disease. Sodium in processed meats may increase blood pressure, which is a risk factor for heart disease. Other chemicals that are used in processed meats may play a role in heart disease as well, by damaging blood vessels.
Red meat has also been linked to increased risks of colorectal and other cancers. Again, heme iron could be a culprit — it is more easily absorbed into the body than other forms of iron, and can cause oxidative damage to cells — as could compounds that are created when meat is cooked at a high temperature. Preservatives used in processed meats also may play a role, scientists have said, because they convert into carcinogenic compounds in the body.