Data extraction of the studies used for the systematic review
| Authors (year), country | Study design | Duration (weeks) | Sample, N (IG/CG) | Mean age (years) (IG/CG) | Male (%) (IG/CG) | HbA1c (%) IG (baseline/end-line) | HbA1c (%) CG (baseline/end-line) | Exposure diet | Comparator diet | Outcomes |
| Wright et al
44
(2017) New Zealand | RCT | 24 | 9* (7/2) | 56 (56/56) | 40.0 (33.3/46.9) | 6.0/5.7 | 5.5/5.7 | Low-fat plant-based | Omnivorous | Quality of life significantly improved in the IG. General and nutritional self-efficacy and self-esteem were significantly greater in the IG than in the CG. Medication usage decreased in the IG, while it increased in the CG. Adherence was significantly greater in the IG. |
| Lee et al
45
(2016) South Korea | RCT | 12 | 93 (46/47) | 58.1 (57.5/58.3) | 19.25 (13.0/25.5) | 7.7/7.1 | 7.4/7.2 | Vegan | Korean Diabetic Association guidelines | Reduction in HbA1c was significantly greater in the IG than in the CG. FBG reduced only in the IG. There was a greater decrease in LDL cholesterol in the IG. Triglycerides increased in the IG and decreased in the CG. The CG reported higher rates of adherence. |
| Bunner et al
41 (2015) USA | RCT | 20 | 34 (17/17) | 57 (57/58) | 44.1 (35.3/53.0) | 8.0/7.2 | 7.8/7.8 | Low-fat plant-based | Omnivorous | Quality of life significantly improved within the IG. Significant improvements in pain were found in the IG. The IG had a significant reduction in HbA1c. Reduction in weight was significantly greater in the IG than in the CG. Total and LDL cholesterol decreased in the IG and increased in the CG. There was a greater increase of triglycerides in the CG. Electrochemical skin conductance in the foot declined in the CG, while it stayed constant in the IG. Adherence in the IG was high. |
| Soare et al 43 (2014) Italy | RCT | 3 | 51 (25/26) | 66 (67/65) | 49.0 (44.0/53.8) | 6.7/6.3 | 6.8/6.6 | Low-fat plant-based | Italian Association of Doctors of Diabetology guidelines | The IG had a significantly greater reduction in HbA1c than the CG. There was a significantly greater weight loss in the IG compared with the CG. FBG significantly decreased within group only in the IG. Total and LDL cholesterol significantly declined only in the IG. Adherence was high in both groups. |
| Mishra et al
39 (2013) USA | CT | 18 | 43† (21/22) | 45.2 (44.3/46.1) | 17.2 (22.5/12.1) | 7.54/6.94 | 7.13/7.05 | Low-fat vegan | Omnivorous | The IG had a significant reduction in HbA1c compared with the CG. Significant improvements in weight were found in participants with T2D. |
| Kahleova et al
35 (2013) Czech Republic | RCT | 24 | 74‡ (37/37) | 56.1 (54.6/57.7) | 47.3 (46.0/49.0) | 7.6/6.95 | 7.7/7.46 | Plant-based | European Association for the Study of Diabetes guidelines | Depression and quality of life significantly improved only in the IG. Dietary disinhibition decreased significantly only in the IG. Dietary restraint increased significantly more in the CG. The IG reported high levels of adherence. |
| Kahleova et al
36 (2011) Czech Republic | RCT | 24 | 74 (37/37) | 56.1 (54.6/57.7) | 47.3 (46.0/49.0) | 7.6/6.95 | 7.7/7.46 | Plant-based | European Association for the Study of Diabetes guidelines | HbA1c significantly decreased only in the IG. Reduction in weight was significant only in the IG. Reduction in LDL cholesterol was significant only in the IG. There was a greater reduction in total cholesterol in the IG. Triglycerides reduced only in the IG, while increased in the CG. |
| Ferdowsian et al 51 (2009) USA | CT | 22 | 19† (10/9) | 44 (46/42) | 17.7 (26.5/4.4) | 7.4/7.1 | 7.0/6.7 | Low-fat vegan | Omnivorous | HbA1c similarly decreased in both groups. Medium adherence was reported in the IG. |
| Barnard et al
37 (2009b) USA | RCT | 74 | 99§ (49/50) | 55.6 (56.7/54.6) | 39.4 (45/34) | 8.05/7.71 | 7.93/7.79 | Low-fat vegan | American Diabetes Association guidelines | Dietary disinhibition and hunger decreased in both groups. Dietary restraint increased in greater degree in the CG than in the IG. Diet satisfaction, adherence and acceptability of diet were similar in both groups. |
| Barnard et al
38 (2009a) USA | RCT | 74 | 99¶ (49/50) | 55.6 (56.7/54.6) | 39.4 (45/34) | 8.05/7.71 | 7.93/7.79 | Low-fat vegan | American Diabetes Association guidelines | HbA1c reduction was greater in the IG than in the CG. Significant weight loss within group was reported in both groups. FBG significantly decreased within group only in the IG. Total cholesterol and LDL cholesterol significantly declined in both groups. Triglycerides significantly decreased only in the IG. |
| Nicholson et al 42 (1999) USA | RCT | 12 | 11 (7/4) | 55.5 (51/60) | 54.5 (57.1/50.0) | 8.3/6.9 | 8.0/7.0 | Low-fat vegan | Conventional low-fat | HbA1c reduction was greater in the IG than in the CG. Weight loss and FBG significantly decreased only in the IG compared with the CG. |
*Number of participants with T2D in the study. For all other characteristic variables, the N is 65 (33/32).
†Number of participants with HbA1c data available. For all other characteristic variables, the N is 291 (142/149).
‡Characteristic variables extracted from Kahleova et al 36 (2011).
§Number of participants with HbA1c data available. For all other characteristic variables, the N is 113 (68/45).
¶Characteristic variables were extracted from Barnard et al 37 38 (2009).
CG, control group; CT, controlled trial; FBG, fasting blood glucose; HbA1c, glycated hemoglobin; IG, intervention group; LDL, low-density lipoprotein; RCT, randomized controlled trial; T2D, type 2 diabetes.