Table 1 Characteristics of prospective cohort studies included in the meta-analysis of whole grain intake and type 2 diabetes in adults

Li et al., 2022 [34]

Women’s Health Initiative Observational Study

1993/1998–2020, 15.8, F, USA

108,681 w, mean age 63 years at baseline: 15,842 cases

validated FFQ, 122 food items

ingredient (g/day)

6.3 g/day, 78.5 g/day

0.84(0.79, 0.88)

Age, residence, energy intake, race/ethnicity, physical activity, smoking status, pack-years of cigarettes, alcohol, HRT, education, income, family history of diabetes, antihypertensive medication use, dietary protein sources, BMI

Hu et al., 2020a [33]

Nurses’ health study

1976–2014, 40, F, USA

69,139 w, 30–55 years: 8170 cases

validated FFQ, 116 items

ingredient (servings/day)

0.1 servings/day, 1.9 servings/day

0.68(0.63, 0.73)

Age, ethnicity, smoking, alcohol, multivitamin use, physical activity, modified alternative healthy eating index, family history of diabetes, HRT, oral contraceptive use, BMI

Hu et al., 2020b [33]

Nurses’ Health study II

1989–2017, 28, F, USA

89,120 w, 25–42 years: 7072 cases

validated FFQ, 116 items

ingredient (servings/day)

0.3 servings/day, 2.5 servings/day

0.73(0.68, 0.8)

Age, ethnicity, smoking, alcohol, multivitamin use, physical activity, modified alternative healthy eating index, family history of diabetes, HRT, oral contraceptive use, BMI

Hu et al., 2020c [33]

Health Professionals Follow-up study

1986–2016, 30, M, USA

36,525 m, 40–75 years: 3387 cases

validated FFQ, 116 items

ingredient (servings/day)

0.2 servings/day, 2.8 servings/day

0.72(0.64, 0.81)

Age, ethnicity, smoking, multivitamin use, physical activity, modified alternative healthy eating index, family history of diabetes, BMI

Kyro et al., 2018 [32]

Danish Diet, Cancer, and Health cohort

1993/1997–2018,15, M&F, Denmark

26,251 m & 29,214 w, 50–65 years: 7417

validated FFQ, 192 food items

ingredient (g/day)

M: 19.45 g/day, 68.85 g/day; F: 19.05 g/day, 59.1 g/day

M: 0.8(0.73, 0.88); F: 0.85(0.77, 0.94)

Age, education, physical activity, smoking, alcohol, red processed meat, menopause, HRT, BMI

Wirstrom et al., 2013 [31]

Swedish middle-aged men and women

1992/1998–2013, 8–10, M&F, Sweden

5477 m/w, 35–56 years: 165 cases

validated FFQ, NA

ingredient (g/day)

16.35 g/day, 73.35 g/day

0.71(0.48, 1.04)

Age, sex, parental history of diabetes, BMI, physical activity, smoking, education, blood pressure

Ericson et al., 2013 [30]

Malmo Diet and Cancer Cohort

1991/1996–2006, 12, M&F, Sweden

27,140 m/w, 45–74 years: 1709 cases

validated diet history, FFQ, 168 food items

products (servings/day)

M: 1 servings/day, 2 servings/day; F: 0.01 servings/day, 2.3 servings/day

M: 0.83(0.67, 1.03); F: 0.85(0.68, 1.06)

Age, dietary method, season, total energy, education, smoking, alcohol, physical activity, BMI

van Dam et al., 2006 [29]

Black Women’s Health Study

1995–2003, 8, F, USA

41,186 w, age 21–69 years: 1964 cases

validated FFQ, 68 food items

products (serving/day)

0.03 servings/day, 1.29 servings/day

0.69(0.6, 0.79)

Age, total energy intake, BMI, smoking, physical activity, alcohol, parental history of diabetes, education, coffee, sugar sweetened soft drink, processed meat, red meat, low-fat dairy

Montonen et al., 2003 [28]

Finnish Mobile Clinic Health Examination Survey

1966/1972–1995, 23, M&F, Finland

2268 m &2030 w, 40–69 years: 52/102 cases

baseline FFQ, > 100 food items

products (g/day)

79 g/day, 302 g/day

0.65(0.36, 1.18)

Age, sex, geographic area, smoking, BMI, total energy intake, fruit, berries and vegetables

Mayer et al., 2000 [27]

Iowa Women’s Health Study

1986–1992, 6, F, USA

35,988 w, 55–69 years: 1141 cases

validated FFQ, 127 food items

products (servings/week)

1 servings/week, 20.5 servings/week

0.79(0.65, 0.96)

Age, total energy intake, BMI, WHR, education, smoking, alcohol, physical activity