Table 3 Subgroup analysis on the effects of whole grains on fasting blood glucose, glycemic hemoglobin and homeostatic model assessment for insulin resistance in adults

Study design

parallel

-0.116(-0.217, -0.014)*

N = 24, I² = 80.85

0.039(-0.334,0.412)

N = 8, I² = 0

-0.118(-0.308, 0.071)

N = 11, I² = 27.39

crossover

-0.086(-0.165, -0.006)*

N = 13, I² = 8.46

-1.889(-3.519,-0.259)*

N = 5, I² = 72.61

-0.307(-0.766, 0.152)

N = 4, I² = 46.46

Intervention duration

≥ 12w

-0.097(-0.199, 0.006)

N = 20, I² = 73.83

0.041(-0.331,0.413)

N = 8, I² = 0

-0.112(-0.338, 0.114)

N = 9, I² = 41.07

< 12w

-0.115(-0.233, 0.004)

N = 17, I² = 71.89

-2.018(-3.683,-0.353)*

N = 5, I² = 71.56

-0.281(-0.564, 0.001)

N = 6, I² = 14.75

Health status

unhealthy

-0.219(-0.409, -0.028)*

N = 14, I² = 84.14

-1.339(-2.598,-0.080)*

N = 7, I² = 71.58

-0.208(-0.453, 0.037)

N = 7, I² = 30.17

generally healthy

-0.061(-0.136, 0.014)

N = 22, I² = 58.76

0.041(-0.369,0.452)

N = 6, I² = 0

-0.123(-0.397, 0.151)

N = 8, I² = 42

Baseline mean of BMI

BMI < 30 kg/m²

-0.102(-0.209, 0.005)

N = 23, I² = 76.01

-1.027(-2.036,-0.017)*

N = 10, I² = 69.46

-0.142(-0.349, 0.065)

N = 10, I² = 26.83

BMI ≥ 30 kg/m²

-0.059(-0.143, 0.024)

N = 11, I² = 39.98

0.062(-0.38,0.505)

N = 3, I² = 0

-0.222(-0.608, 0.164)

N = 5, I² = 53.7

Baseline mean of age

age < 50

-0.098(-0.199, 0.003)

N = 18, I² = 69.85

-0.423(-1.071,0.225)

N = 6, I² = 33.75

-0.103(-0.441, 0.236)

N = 6, I² = 54.9

age ≥ 50

-0.121(-0.199, 0.003)

N = 17, I² = 77.55

-0.866(-2.177,0.446)

N = 7, I² = 77.02

-0.198(-0.405, 0.01)

N = 9, I² = 17.24

Baseline mean of triglycerides

TG ≥ 1.7

mmol/L

-0.364(-0.737, 0.008)

N = 6, I² = 86.44

NA

-0.347(-0.809, 0.116)

N = 4, I² = 56.94

TG < 1.7

mmol/L

-0.061(-0.13, 0.009)

N = 8, I² = 10.2

-0.198(-0.674,0.277)

N = 5, I² = 26.34

0.062(-0.148, 0.272)

N = 6, I² = 0

Whole grain products variety

1–2

-0.144(-0.287, -0.001)*

N = 23, I² = 80.60

-0.836(-1.818,0.147)

N = 10, I² = 68.06

-0.120(-0.413, 0.174)

N = 7, I² = 54.72

≥ 5

-0.101(-0.154, -0.048)***

N = 14, I² = 19.41

-0.414(-1.344,0.516)

N = 3, I² = 61.71

-0.229(-0.440, -0.019)*

N = 8, I² = 0

Whole grain types

Rice

-0.305(-0.564, -0.045)*

N = 11, I² = 86.66

-1.123(-2.922,0.675)

N = 6, I² = 78.87

-0.324(-0.729, 0.082)

N = 4, I² = 57.44

Wheat

0.019(-0.130, 0.168)

N = 8, I² = 68.27

NA

-0.005(-0.267, 0.258)

N = 4, I² = 0

Others

-0.164(-0.434, 0.106)

N = 6, I² = 59.92

-0.439(-1.566,0.689)

N = 3, I² = 0

NA

Mix

-0.092(-0.148, -0.035)**

N = 12, I² = 22.95

-0.414(-1.344,0.516)

N = 3, I² = 61.71

-0.261(-0.540, 0.019)

N = 6, I² = 22.57

Study quality

Low risk

-0.153(-0.254,- 0.053)**

N = 25, I² = 77.37

-0.424(-0.899,

0.051)

N = 7, I² = 0

-0.089(-0.251,

0.073)

N = 12, I² = 19.23

Uncertain

-0.091(-0.189, 0.007)

N = 7, I² = 24.51

-0.151(-0.429,

0.127)

N = 3, I² = 90.43

NA

High risk

-0.082(-0.059,

0.223)

N = 5, I² = 37.73

0.170(-1.263

1.639)

N = 3, I² = 34.18

NA