Dietary Patterns and Cardiovascular Diseases in Individuals with Type 2 Diabetes: A Systematic Review and Meta-Analysis of Prospective Observational Studies

Individuals with type 2 diabetes are at increased risk of cardiovascular diseases (CVD). Dietary behavior plays an important role in both the management of diabetes and the prevention of CVD. We aimed to summarize the current evidence on associations between dietary patterns and the risk of CVD outcomes in individuals with type 2 diabetes. PubMed, Embase, and Cochrane Library were systematically searched for prospective observational studies investigating dietary patterns in association with CVD outcomes in individuals with diabetes. Summary risk ratios (SRR) with 95% confidence intervals (CIs) were calculated using random effects model. The certainty of evidence was evaluated using the Grading of Recommendations, Assessment, Development, and Evaluation approach. In total, we identified 57 studies. Moderate certainty of evidence was found for the association between the Mediterranean diet and CVD (SRR per 1 point: 0.95; 95% CI: 0.93, 0.97; n = 6). Other plant-based diets such as the Dietary Approaches to Stop Hypertension (per 5 points: 0.96; 95% CI: 0.89, 1.03; n = 3), EAT-Lancet diet (per 3 points: 0.65; 95% CI: 0.45, 0.95, n = 3) or country-specific dietary guidelines (high compared with low: 0.80; 95% CI: 0.76, 0.84; n = 9) were associated with a lower incidence of CVD outcomes (low or very low certainty of evidence). Higher adherence to the unhealthy plant-based index and dietary inflammatory index was positively associated with CVD (low and very low certainty of evidence). No clear associations were found for overall and vegetable-based plant-based index, low-carbohydrate diets, glycemic load, glycemic index, and CVD in persons with type 2 diabetes. Most studies were rated as high risk of bias due to confounding. In conclusion, the results suggest a possible beneficial association between plant-based dietary patterns and CVD outcomes in individuals with type 2 diabetes. However, the certainty of evidence was low to very low, highlighting the need for further well-designed prospective studies. This trial was registered at PROSPERO as CRD42018110669.