Metabolic Effects of Monounsaturated Fatty Acid–Enriched Diets Compared With Carbohydrate or Polyunsaturated Fatty Acid–Enriched Diets in Patients With Type 2 Diabetes: A Systematic Review and Meta-analysis of Randomized Controlled Trials

OBJECTIVE: Dietary interventions in patients with type 2 diabetes (T2D) are important for preventing long-term complications. Although a healthy diet is crucial, there is still uncertainty about the optimal macronutrient composition. We performed a meta-analysis comparing diets high in cis-monounsaturated fatty acids (MUFA) to diets high in carbohydrates (CHO) or in polyunsaturated fatty acids (PUFA) on metabolic risk factors in patients with T2D. RESEARCH DESIGN AND METHODS: We systematically reviewed PubMed, MEDLINE, and Cochrane databases and prior systematic reviews and meta-analyses to identify interventions assessing HbA1c, fasting plasma glucose and insulin, LDL and HDL cholesterol, triglycerides, body weight, or systolic/diastolic blood pressure. Meta-analyses were conducted using both fixed- and random-effects models to calculate the weighted mean difference (WMD) and 95% CI. RESULTS: We identified 24 studies totaling 1,460 participants comparing high-MUFA to high-CHO diets and 4 studies totaling 44 participants comparing high-MUFA to high-PUFA diets. When comparing high-MUFA to high-CHO diets, there were significant reductions in fasting plasma glucose (WMD -0.57 mmol/L 95% CI -0.76, -0.39), triglycerides (-0.31 mmol/L -0.44, -0.18), body weight (-1.56 kg -2.89, -0.23), and systolic blood pressure (-2.31 mmHg -4.13, -0.49) along with significant increases in HDL cholesterol (0.06 mmol/L 0.02, 0.10). When high-MUFA diets were compared with high-PUFA diets, there was a significant reduction in fasting plasma glucose (-0.87 mmol/L -1.67, -0.07). All of the outcomes had low to medium levels of heterogeneity, ranging from 0.0 to 69.5% for diastolic blood pressure (Phet = 0.011). CONCLUSIONS: Our meta-analysis provides evidence that consuming diets high in MUFA can improve metabolic risk factors among patients with T2D.