During 2,050,071 person-years of follow-up from 1980 through 2006, we documented 2210 nonfatal infarctions and 952 deaths from coronary heart disease. Our follow-up rate (defined as person-years contributed by study participants until their last returned FFQ or death divided by person-years contributed by study participants until death) was 97%. Between 1980 and 2002, red meat consumption decreased from a median intake of 1.06 to 0.49 servings/day, while poultry consumption increased from 0.14 to 0.28 servings/day and fish consumption remained unchanged. Characteristics of the study participants during the 26 years of follow-up, averaged according to proportion of person-time in each fifth of intake, are shown in . High red meat consumption was associated with higher rates of smoking, angina, hypertension, hypercholesterolemia, diabetes, lower physical activity, increased intake of trans fat, and decreased intake vitamin E and multivitamins. The major groups of protein sources were not highly correlated with each other: the Spearman correlation coefficient of red meat with poultry was −0.09; red meat with fish −0.17; and poultry with fish 0.39.
Age-standardized characteristics of study participants, 1980-2006*
In age-adjusted analyses, higher intakes of red meat, red meat excluding processed meat, red meat to poultry ratio, red meat to poultry plus fish ratio, and high-fat dairy were significantly associated with increased risk of CHD. Higher intakes of poultry, fish, and low-fat dairy sources were significantly associated with decreased risk (). When we controlled for age, follow-up period, and smoking status, the significant associations seen in the age-adjusted analyses remained. In multivariable analyses () which adjusted for dietary and non-dietary cardiovascular disease risk factors, the associations were reduced in magnitude but remained significant for all the protein groups except low-fat dairy. Fruit and vegetable intake was only weakly to moderately correlated with intake of all the major protein sources and further adjustment for it had no effect on the risk associations. Egg intake was not associated with risk in either age-adjusted or multivariable models.
Relative Risks (RR) and 95% confidence intervals for coronary heart disease according to fifths of intake of major sources of dietary protein
In age-adjusted analyses, animal protein was associated with increased risk and vegetable protein was associated with decreased risk (animal protein relative risk (RR) across fifths: 1.00, 0.94, 0.96, 0.96, 1.14, p for trend 0.01; vegetable protein RR across fifths: 1.00, 0.84, 0.77, 0.69, 0.62, p for trend <0.0001). In the multivariable analyses, vegetable protein but not animal protein remained significantly associated with decreased risk (vegetable protein RR across fifths: 1.00, 0.88, 0.85, 0.80, 0.72, p for trend <0.001). However, when we included polyunsaturated fat, monounsaturated fat, and saturated fat in the multivariable models, we found no relation between animal or vegetable protein and CHD risk.
When we continued updating a participant’s diet even after she had been diagnosed with angina, diabetes, hypertension, hypercholesterolemia, cancer, or stroke, or had a coronary artery bypass, we saw similar associations with red meat as when we stopped updating diet at these diagnoses (relative risk for highest fifth = 1.31, 95% CI 1.15 −1.50, p for trend < 0.0001); however, poultry, fish, and high-fat dairy were no longer associated with CHD risk. When we stopped updating diet at the diagnosis of an intermediate outcome and also controlled for their presence in the multivariable model, red meat, poultry, fish, and high-fat dairy all remained significantly related to risk of CHD.
In the analyses of individual protein sources, higher intake of the red and processed meats were associated with increased risk, while higher intakes of fish, nuts, and beans were associated with decreased risk (). When compared to one serving/day of red meat, one serving/day of nuts, fish, poultry, or dairy was associated with a decreased risk of CHD (). One serving/day of nuts was associated with a 30% (95% CI: 17% to 42%) lower risk of CHD when compared to one serving/day of red meat. Similarly, when compared to one serving/day of red meat, one serving/day of low-fat dairy was associated with a 13% (95% CI: 6% to 19%) lower risk, one serving/day of poultry was associated with a 19% (95% CI: 3% to 33%) lower risk, and one serving/day of fish was associated with a 24% (95% CI: 6% to 39%) lower risk.
Relative Risks (RR) and 95% confidence intervals for coronary heart disease according to fifths of intake of Individual types of red meat, poultry, and fish
Relative risks and 95% confidence intervals for coronary heart disease associated with replacement of major dietary protein source for another
When compared to one serving/day of fish, one serving/day of dairy products was associated with an increased risk, while one serving/day of nuts or beans was not significantly associated with risk.