Table 1.
Systematic reviews and meta-analysis of the association between the Mediterranean diet and type 2 diabetes (T2D) 2013–2020.
| Author, Year of Publication, Type of Study, Reference | Intervention, Participants | Evaluation, Follow Up | Results/Conclusion |
|---|---|---|---|
| Ajala, O. 2013, 20 RCTs [41] | Low carbohydrate, Low GI, MedDiet, High protein diet Adults with type 2 diabetes or obesity | HbA1c Weight loss, >6 months | All diets improved glycemic parameters (glycated hemoglobin reductions of −0.12% LC (p = 0.04), −0.14% Low GI (p = 0.008), −0.47% MedDiet (p < 0.00001), and −0.28% High protein (p < 0.00001)). Low-carbohydrate and MedDiet led to significant loss in weight (−0.69 kg (p = 0.21) and −1.84 kg (p < 0.00001), respectively). Increase in HDL was noted in all diets except the high-protein diet. |
| Carter, P. 2014, SR, MA 8 RCTs, [42]. | MedDiet, Paleo diet, Control diet Overweight and/or high cardiovascular risk and/or type 2 diabetes | Glycemic control, HbA1c, Insulin, 2–12 months | MedDiet superior compared to the control group, except when compared to the paleo diet. None of the diets proved preferable regarding the basal glucose levels. |
| Koloverou, E. 2014, SR, MA 1 RCT, 9 prospective studies [43]. | MedDiet, Control diet Healthy adults with or without CV/T2D | Incidence of type 2 diabetes, 3.5–14 years | Higher adherence to the MedDiet was associated with 23% reduced risk of developing type 2 diabetes (combined relative risk for upper versus lowest available centile: 0.77; 95% CI: 0.66, 0.89) |
| Esposito, K. 2014, MA 8 prospective studies, 30 cohorts. [44]. | MedDiet, Dietary Approach to Stop Hypertension (DASH) Adults |
Incidence of type 2 diabetes, 3.2–23 years | Both diets presented themselves as a healthy dietary pattern, however comparison between MedDiet and. DASH showed no changes in incidence of type 2 diabetes. |
| Emadian, A. 2015, SR 11 RCTs [45]. | MedDiet, Vegan diet, Low glycemic index diet Overweight adults and type 2 diabetes | Glycemic control, HbA1c, >6 months | All diet groups resulted beneficial, with improved overall glycemic control by reduction of HbA1c levels. |
| Esposito, K. 2015, SR 8 MA, 5 RCTs [46] | MedDiet Control diet Adults with type 2 diabetes or at risk | Incidence of type 2 diabetes Glycemic control, >6 months | MedDiet improves glycemic control by reducing HbA1c 0.3–0.47% compared with low-fat diet. MedDiet has a significant reduction of incidence of future type 2 diabetes ranging from 19% up to 23% |
| Huo, R. 2015, MA 9 RCTs [47]. | MedDiet Adults with type 2 diabetes | Glycemic control. HbA1c, insulin, Homeostatic Model Assessment for Insulin Resistance (HOMA), 1 month–4 years | The MedDiet group had a significant reduction of HbA1c levels (MD−0.30; 95% CI −0.46, −0.14), glucose levels (MD −0.72 mmol/L; CI −1.24, −0.21), and baseline insulin levels (MD −0.55 μU/mL; CI −0.81, −0.29). |
| Schwingshackl, L. 2015, SR, MA 1 RCT, 8 prospective studies [19]. | MedDiet Healthy adults or with CV risk factors | Incidence of type 2 diabetes, 3.2–20 years | Adherence to MedDiet inversely associated with a decrease in T2D incidence (high vs. low. RR: 0.81; 95% CI 0.73, 0.90, p < 0.0001) |
| Jannasch, F. 2017, SLR, MA 48 articles compromising 16 cohorts/ACRs [16]. | MedDiet, DASH, Alternate Healthy Eating Index (AHEI) Healthy adults |
Incidence of type 2 diabetes, 4.1–23 years | Adherence to MedDiet (RR quantiles: 0.87; 95% CI: 0.82, 0.93), DASH (RR: 0.81; 95% CI: 0.72, 0.92), and AHEI (RR: 0.79; 95% CI: 0.69, 0.90) associated with a significant risk reduction of type 2 diabetes |
| Martinez-Lacoba, R. 2018, SMR 9 SR, 24 MA [48] | MedDiet Adults | Diet adherence, obesity, body weight type 2 diabetes, >6 months | In summary, a MedDiet pattern may help to prevent and manage type 2 diabetes. |
| Schwingshackl, K. 2018, SR, MA 56 RCTs [49] | Low-fat diet or vegan, MedDiet, LC, paleolithic hyperprotein diet Adults with T2D | Glycemic control HbA1c Weight change, 3–48 months | The MedDiet overall superior when compared to the other dietary approaches, by reducing the HbA1c (80%) and reducing the fasting plasma glucose (88%). |
| Zheng M. 2018 SR, 6 RCTs [50] | Modified MedDiet Adults with obesity | Glycemic control HbA1c, >3 months | Low-CHO MedDiet and MedDiet using virgin olive oil had a positive impact on the prevention of overweight patients within T2D |
| Becerra-Tomas, N. 2019, SR, MA 3 RCTs, 38 cohorts, [51]. | MedDiet Adults with type 2 diabetes | CVD incidence, myocardial infarction, CVD mortality, coronary heart disease incidence, >6 months | Beneficial effect on total CVD incidence (RR: 0.62; 95% CI: 0.50, 0.78) and total myocardial infarction (MI) incidence (RR: 0.65; 95% CI: 0.49, 0.88). Highest versus lowest categories of MedDiet adherence, revealed an inverse association with total CVD mortality (RR: 0.79; 95% CI: 0.77, 0.82), coronary heart disease (CHD) incidence (RR: 0.73; 95% CI: 0.62, 0.86), CHD mortality (RR: 0.83; 95% CI: 0.75, 0.92), stroke incidence (RR: 0.80; 95% CI: 0.71, 0.90), stroke mortality (RR: 0.87; 95% CI: 0.80, 0.96) and MI incidence (RR: 0.73; 95% CI: 0.61, 0.88). |
MedDiet = Mediterranean diet, GI = glycemic index, LC = low carb, DASH = dietary approach to stop hypertension, AHEI = alternate healthy eating index, CHO = carbohydrate CVD = cardiovascular disease, RR = risk ratio, CHD = coronary heart disease, MI = Myocardial infarction, HbA1c = glycated hemoglobin A1c, MD = mean difference, MA = meta-analysis, SR = structured review, RCT = randomized control trial; SMR = systematic meta-review.