Red meat consumption and risk factors for type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND OBJECTIVES: Results from observational studies suggest an association of red meat intake with risk of type 2 diabetes mellitus (T2D). However, results from randomized controlled trials (RCTs) have not clearly supported a mechanistic link between red meat intake and T2D risk factors. Therefore, a systematic review and meta-analysis were conducted on RCTs evaluating the effects of diets containing red meat (beef, pork, lamb, etc.), compared to diets with lower or no red meat, on markers of glucose homeostasis in adults. METHODS: A search of PubMed and CENTRAL yielded 21 relevant RCTs. Pooled estimates were expressed as standardized mean differences (SMDs) between the red meat intervention and the comparator intervention with less or no red meat. RESULTS: Compared to diets with reduced or no red meat intake, there was no significant impact of red meat intake on insulin sensitivity (SMD: −0.11; 95% CI: −0.39, 0.16), insulin resistance (SMD: 0.11; 95% CI: −0.24, 0.45), fasting glucose (SMD: 0.13; 95% CI: −0.04, 0.29), fasting insulin (SMD: 0.08; 95% CI: −0.16, 0.32), glycated hemoglobin (HbA1c; SMD: 0.10; 95% CI: −0.37, 0.58), pancreatic beta-cell function (SMD: −0.13; 95% CI: −0.37, 0.10), or glucagon-like peptide-1 (GLP-1; SMD: 0.10; 95% CI: −0.37, 0.58). Red meat intake modestly reduced postprandial glucose (SMD: −0.44; 95% CI: −0.67, −0.22; P < 0.001) compared to meals with reduced or no red meat intake. The quality of evidence was low to moderate for all outcomes. CONCLUSIONS: The results of this meta-analysis suggest red meat intake does not impact most glycemic and insulinemic risk factors for T2D. Further investigations are needed on other markers of glucose homeostasis to better understand whether a causal relationship exists between red meat intake and risk of T2D. PROSPERO REGISTRATION: CRD42020176059