The study was published online Monday in Archives of Internal Medicine.
The study results also showed that substituting other healthy protein sources, such as fish, poultry, nuts and legumes, was associated with a lower risk of mortality.
The researchers prospectively observed 37,698 men from the Health Professionals Follow-up Study for up to 22 years, and 83, 644 women in the Nurses' Health Study for up to 28 years. The study subjects were free of cardiovascular disease (CVD) and cancer at baseline. Diets were assessed through questionnaires every four years.
A combined 23,926 deaths were documented in the two studies, of which 5,910 were from CVD and 9,464 from cancer. Regular consumption of red meat, particularly processed red meat, was associated with increased mortality risk. One daily serving of unprocessed red meat (about the size of a deck of cards) was associated with a 13-percent increased risk of mortality, and one daily serving of processed red meat (one hot dog or two slices of bacon) was associated with a 20-percent increased risk.
Among specific causes, the corresponding increases in risk were 18 percent and 21 percent for cardiovascular mortality, and 10 percent and 16 percent for cancer mortality. These analyses took into account chronic disease risk factors such as age, body mass index, physical activity, and family history of heart disease or major cancers.
According to the study, red meat, especially processed, contains ingredients that have been linked to increased risk of chronic diseases, such as cardiovascular disease and cancer. These include heme iron, saturated fat, sodium, nitrites, and certain carcinogens that are formed during cooking.
Replacing one serving of total red meat with one serving of a healthy protein source was associated with a lower mortality risk: seven percent for fish, 14 percent for poultry, 19 percent for nuts, 10 percent for legumes, 10 percent for low-fat dairy products, and 14 percent for whole grains.
The researchers estimated that 9.3 percent of deaths in men and 7.6 percent in women could have been prevented at the end of the follow-up if all the participants had consumed less than half a serving per day of red meat.
"Our study adds more evidence to the health risks of eating high amounts of red meat, which has been associated with type 2 diabetes, coronary heart disease, stroke, and certain cancers in other studies," said lead author An Pan, research fellow in the Department of Nutrition at HSPH.