Studies showing a positive association of high consumption of processed and unprocessed red meat with the incidence of cardiovascular disease
Several studies have demonstrated a positive association with high consumption of unprocessed and processed red meat and the incidence of CVD and cardiovascular (CV) mortality. These studies are listed in table 1 and they will be, briefly, discussed here. The study by Zheng et al [6], is a prospective cohort study of 81,469 US men and women ages 59-61 years on the effects of high consumption of unprocessed and processed red meat and incidence of CV mortality. After a mean follow-up of 14.7 years, the highest consumption (> 05 servings/day) of unprocessed red meat was associated with a 10% higher incidence of CV mortality, HR 1.10 (95% CI 1.04- 1.17, p < 0.001)), whereas the highest consumption of processed meat was associated with a 13% higher incidence of CV mortality, HR 1.13 (95% CI 1.04-1.23, p < 0.001) compared to those with the lowest meat consumption. In another prospective cohort study, Pan et al [21], analyzed the effects of red meat consumption on all-cause mortality in 121,342 men and women ages 52-54 free of CVD at baseline. After 22 years of follow-up and multivariate adjustments, one serving of unprocessed or processed red meat was associated with 13% and 20% increase in all-cause mortality, HR 1.13 (95% CI 1.07-1.20), and 1.20 (95% CI 1.15-1.24), respectively. The corresponding percentages for CV mortality were 18% and 21%, HR 1.18 (95% CI 1.13-1.23) and 1.21 (95% CI 1.13-1.31) for unprocessed and processed red meat, respectively. Also, in a case-controlled study, Wang et al [22], examined the relationship between unprocessed, processed, and total red meat consumption with the incidence of CAD and fatal and nonfatal myocardial infarction (MI) in 2,131 Costa Rican patients mean age 58.1 years. After 10 years of follow-up, the odds ratio (OR) for the onset of acute MI were higher in the 5th quintile (11o.8 g/day) than the 1st quintile, OR 1,29 (95% CI 1.01-1.65) for processed meat and OR 1.31 (95% CI 1.04-1.65) for total red meat consumption, respectively. Regarding the influence of sex on the incidence of MI, women had higher incidence than men, OR 1.47 (95% CI 0.80-2.69). In another prospective cohort study, Key et al [23], examined the effects of meat on the incidence of ischemic heart disease (IHD) in 409,885 subjects ages 51-61 years, from the Pan-European Epic Cohort study. After 12.6 years of follow-up, the incidence of IHD between the top 5th and bottom 5thof unprocessed or processed red meat consumption was increased by 10% and 13 %, HR 1.10 (95% CI 0.99-1.21) and HR 1.13 (95% CI 1.02-1.26) for unprocessed and processed red meat, respectively. In contrast, the consumption of fish, poultry, milk, or eggs were not associated with an increased incidence of IHD. Similarly, a prospective cohort study by Alshahrami et al [24], examined the effects of unprocessed or processed red meat on the incidence of CV mortality and all-cause mortality in 96,000 subjects from the Seventh –day Adventist faith 53-57 years. After a mean follow-up of 11.8 years, unprocessed red meat was associated with increased incidence of CV mortality and all-cause mortality, HR 1.26 (95% CI 1.05-1.50) and HR 1.18 (95% CI 1.07-1.31), respectively. Processed red meat alone was not associated with an increased incidence of CV mortality, but the combination of unprocessed and processed red meat was, HR 1.23 (95% CI 1.11-1.36). Also, a recent study by Zhong et al [25], analyzed the of data from 6 US prospective cohort studies of 29,682 subjects mean age 53.7 years, the effects of red meat, poultry, or fish consumption on the incidence of the composite endpoint of (CHD, stroke, HF, CVD, all-cause death). After 19 years of follow-up, there was a positive association of red meat (processed and unprocessed), and poultry, but not fish on the incidence of CVD and all-cause mortality. The adjusted HR (aHR) for CVD was 1.07 (95% CI1.04-1.11) for processed red meat, aHR 1.03 (95% CI 1.01-1.06) for unprocessed red meat, and aHR 1.04 (95% CI 1.01-1.06) for poultry. Also processed and unprocessed red meat had a positive association with all-cause mortality, aHR 1.03 (95% CI 1.02-1.05), aHR 1.03 (95% CI 1.01-1.05), respectively. In contrast, poultry or fish consumption were not associated with an increase in all-cause mortality.
Similar effects were demonstrated by several reviews and meta-analyses. The review and meta-analysis by Micha et al [26], consists of 20 studies (17 prospective and 3 case control), involving 1,218,380 subjects on the effects of high meat consumption ( ≥ 100 g/day) on the incidence of CHD. In this review, unprocessed red meat consumption was not associated with an increased incidence of CHD, HR 1.00 (95% CI 0.81-1.23, p = 0.36) whereas, processed meat consumption was associated with a 42% higher risk of CHD, HR 1.42 (95% CI 1.07-1.89, p = 0.04). Associations were intermediate for total meat intake. In a review and meta-analysis of prospective studies involving 1,330,352 subjects ages 20-86 years, Larsson et al [27], analyzed the effects of unprocessed and processed red meat consumption on all-cause mortality. After a follow-up of 9-28 years and multivariate adjustment analyses, the highest vs the lowest consumption of unprocessed or processed red was associated with 10%, HR 1.10 (95% CI 0.98-1.22) and 29%, HR 1.29 (95% CI 1.24-1.35) higher incidence of ACM, respectively. The study by Bellavia et al [28], is a prospective study of 109,201 Swedish men and women ages 45-79 years. After a mean follow-up of 15 years, those subjects consuming > 100 g of unprocessed meat/day had a shorter survival than those never consuming red meat. The HRs for total red meat consumption were HR 1.16 (95% CI 1.06-1.127) for 150 g/day, HR 1.26 (95% CI 1.14-1.40) for 200 g/day, HR 1.37 (95% CI 1.21-1.36) for 250 g/day, and HR 1.49 (95% CI 1.27- 1.75) for 300 g/day, respectively. This study demonstrated a dose-response association of total red meat consumption with short term survival. The review and meta-analysis of 13 prospective cohort studies involving 1,674,272 subjects ages 18-92 years, by Abete et al [29], concerns the association of consumption of unprocessed and processed red, white and total meat with mortality from CVD, IHD, and all-cause mortality. The analysis of results from these studies, showed that high consumption of unprocessed or processed red meat was associated with an increased incidence of CVD mortality, 16% relative risk (RR), 1.16 (95% CI 1.03-1.32, p < 001) for unprocessed red meat, and 18%, RR 1.18 (95% CI 1.05-1.32, p < 0.002) for processed meat, respectively. Regarding the IHD mortality, processed but not unprocessed red meat consumption, was associated with a statistically increased IHD mortality, RR 1.52 (95% CI 0.50-4,66, p = 0.004) for processed and RR 1.02 (95% CI 0.72-1.46) for unprocessed red meat, respectively. Also, total red meat, but not white meat consumption was associated with increased IHD mortality, RR 1.52 (95% CI 0.68-3.40) for total and RR 1.00 (95% CI 0.82-1.21) for white meat, respectively. Regarding the consumption of processed meat, this was associated with increased all-cause mortality, RR 1.22 (95% CI 1.16-1.29), but not the total red and white meat consumption. Also, processed red meat was positively associated with increased all-cause mortality in both men and women.