Studies Showing an Association of Red Meat Consumption and T2DM
Several studies have also, shown an association between unprocessed or processed red meat consumption and incidence of T2DM. These studies are summarized in table 4 and they will be briefly, discussed here. The study by Liu et al [37], is prospective cohort study of 59,033 women ages 30-55 years, free of CVD and T2DM at baseline. After a mean follow-up of 17.3 years, and multivariate adjustments for red meat cooking methods, total red meat intake, processed or unprocessed ≥ 2 times/week vs < 1 time/month, were associated with an increased risk of T2DM ( p< 0.05) for all. However, the higher frequency of broiling it or barbequing it had a greater impact on the risk of T2DM ( p < 0.001) compared to stewing or boiling it. This study demonstrated that high temperature or open-flame cooking of red meat, may further increase the risk for T2DM. The study by Du et al [38], is a prospective Chinese study from the China Kadoorie Biobank of 512,000 subjects mean age 51 years. At baseline a computer-based method was used to collect information about frequency of consumption of red meat, poultry, fish, fresh fruit and other items. Also, at baseline, the participants reported regular consumption (≥ 4 days/week) of red meat by 47.0%, poultry by 1.3%, or fish by 9.9%. After a mean follow-up of 9.0 years, and adjusting for adiposity and other confounders, each 50 g/day increase in consumption of red meat or fish was associated with 11% and 6% increase in risk for T2DM, HR 1.11 (95% CI 1.04-1.20) and HR 1.06 (95% CI 1.00-1.13) for red meat and fish, respectively. In addition, the association was higher in men and women from urban areas, HR 1.42 (95% CI 1.15-1.74) for red meat and HR 1.18 (95% CI 1.03-1.36) for fish, respectively compared to those living in non-urban areas. No association was noted between poultry consumption and risk for T2DM, HR 0.96 (95% CI 0.83-1.12). The study by Pan et al [39] is also, a prospective cohort study involving 26,357 men from the Health Professionals Follow-up Study (HPFS, 196-2006)), 48,709 women from the Nurses Health Study (NHS, 1986-2006), and 74,077 women from the (NHS II, 191-2007) study, which evaluated the effects of red meat consumption with the incidence of T2DM. After a mean follow-up of 17.1 years, the increase in red meat intake by 0.5 servings/day from baseline, was associated with a 48% increase in the incidence of T2DM, pHR 1.48 (95% CI 1.37-1.59) after multiple adjustments, compared to a control group, who did not change the red meat consumption. In contrast, reduction of red meat consumption by 0.5 servings/day from baseline, decreased the incidence of T2DM by 14% in the next 4 years, HR 1.14% (95% CI 7%-20%). Also, the study by Bondinelli et al [40], is a prospective case-control study of 340,234 adult subjects on the association of meat consumption and incidence of T2DM in the EPIC-InterAct Study. After 11.7 years of follow-up, 12,403 cases of incident T2DM were identified. In this large study, a dose-response association between red meat consumption and incidence of T2DM was found. In quintiles 1-5, the unprocessed red meat consumption was 18.6 g/day, 32,8 g/day, 45.6 g/day, 58.7 g/day and 81.5 g/day. For Q1 the HR for new onset T2DM was 1.00, and for quintiles 2-5 the HRs for new onset T2DM was 1.16 (95% CI 1.07-1.27), 1.26 (95% CI 1.36-1.38), 1.40 (95% CI 1.27-1.53), and 1.57 (95% CI 1.42-1.73), p < 0.0001) for each 50 g/day increments of unprocessed red meat. The processed meat consumption for quintiles 1-5, was 19.4 g/day, 28.4 g/day, 32.7 g/day, 39.0 g/day, and 56.2 g/day, and the HRs for new onset T2DM, were 1.00, 1.13 (95% CI 1.04-1.22), 1.20 (95% CI 1.10-1.30), 1.36 (95% CI 1.25-1.48), and 1.61 (95% CI 1.47-1.76), p < 0.0001 for linear trend. This study confirms a positive association between high consumption of unprocessed and processed red meat and incidence of T2DM. In a review and meta-analysis, Tian et al [41] analyzed the effects of consumption of red meat as well as other foods on the incidence of T2DM. This review included 483,174 subjects of whom, 52,637 developed T2DM. In these subjects, the pRR for new onset T2DM was 1.22 (95% CI 1.09-1.36) for unprocessed red meat consumption, and 1.39 (95% CI 1.29-1.49) for processed meat consumption. In contrast, th pRR for new onset T2DM with consumption of other foods was, 0.96 (95% CI 0.88-1.06) for plant protein, 1.03 (95% CI 0.89-1.17) for fish, 1.03 (95% CI 0,64-1.67) for eggs, and 0.89 (95% CI for total dairy foods. This review clearly demonstrates the benefits of healthy food consumption on the incidence of new onset T2DM.