Table 2.
Subgroup analyses of fasting glucose and insulin concentrations stratified by previously defined study characteristics
| Variables | Fasting glucose | Fasting insulin | ||||||
|---|---|---|---|---|---|---|---|---|
| No. trials | Net change (95% CI) (mmol/L) | Test of heterogeneity † | No. trials | Net change (95% CI) (mIU/mL) | Test of heterogeneity † | |||
| P | I 2 (%) | P | I 2 (%) | |||||
| Study design | ||||||||
| Parallel | 18 | −0.07 (−0.10, 0.02) | 0.012 | 46.3 | 15 | 0.28 (−0.24, 0.80) | 0.985 | 0.0 |
| Cross‐over | 14 | −0.07 (−0.15, 0.00) | 0.874 | 0.0 | 12 | −0.74 (−1.39, −0.08) | 0.832 | 0.0 |
| Duration of intervention | ||||||||
| <8 weeks (lower than median) | 19 | −0.06 (−0.14, 0.01) | 0.443 | 1.3 | 16 | −0.45 (−1.08, 0.18) | 0.892 | 0.0 |
| ≥8 weeks (higher than median) | 11 | −0.05 (−0.11, 0.01) | 0.038 | 50.6 | 11 | 0.13 (−0.41, 0.66) | 0.762 | 0.0 |
| Type of whole grain | ||||||||
| Mixed | 13 | −0.10 (−0.17, −0.03) | 0.837 | 0.0 | 11 | −0.38 (−1.10, 0.35) | 0.370 | 7.8 |
| Others | 19 | −0.01 (−0.07, 0.06) | 0.057 | 33.6 | 19 | −0.01 (−0.49, 0.50) | 0.979 | 0 |
| Dose of whole grain | ||||||||
| Higher | 12 | −0.08 (−0.15, −0.02) | 0.293 | 14.3 | 10 | 0.15 (−0.40, 0.70) | 0.936 | 0.0 |
| Lower | 12 | −0.03 (−0.12, 0.06) | 0.117 | 34.1 | 9 | 0.04 (−0.90, 0.99) | 0.857 | 0.0 |
| Baseline mean of BMI | ||||||||
| Obese (≥30 kg/m2) | 11 | −0.07 (−0.14, 0.01) | 0.368 | 8.0 | 10 | −0.09 (−0.68, 0.50) | 0.364 | 8.4 |
| Non‐obese (<30 kg/m2) | 21 | −0.06 (−0.14, 0.02) | 0.055 | 33.3 | 17 | −0.14 (−0.70, 0.42) | 0.959 | 0.0 |
| Weight change | ||||||||
| Yes | 12 | −0.01 (−0.08, 0.07) | 0.254 | 17.8 | 11 | −0.16 (−0.40, 0.72) | 1.00 | 0.0 |
| No | 15 | −0.06 (−0.12, 0.01) | 0.307 | 13.1 | 12 | −0.27 (−0.95, 0.41) | 0.241 | 20.6 |
| Glucose | ||||||||
| Normal glycemia | 25 | −0.05 (−0.10, −0.003) | 0.165 | 20.4 | 21 | −0.03 (−0.49, 0.42) | 0.771 | 0.0 |
| Hyperglycemia | 7 | −0.07 (−0.30, 0.17) | 0.160 | 33.6 | 6 | −0.42 (−1.30, 0.46) | 0.907 | 0.0 |
| Risk of bias | ||||||||
| High | 8 | −0.07 (−0.11, 0.02) | 0.759 | 0.0 | 7 | −0.03 (−0.93, 0.99) | 0.800 | 0.0 |
| Others | 24 | −0.06 (−0.10, 0.11) | 0.049 | 21.3 | 20 | −0.15 (−0.60, 0.30) | 0.907 | 0.0 |
†
P for heterogeneity was assessed by using Cochran's test, and P < 0.1 was considered to show significant heterogeneity across studies. The I 2 statistic was calculated by using Cochran's test, and I 2 > 50% was considered to show significant heterogeneity across studies.