Table 1.
Characteristics of included studies on fruit and vegetable intake and risk of type 2 diabetes
| No | No of cases/non-cases | Age (years) | Measure of intake | Confounders measured | Follow-up (years) | Assessment of type 2 diabetes | Quantity (highest v lowest intakes as servings/day) | Quality score | |
|---|---|---|---|---|---|---|---|---|---|
| Villegas et al 2008,36 Shanghai Women’s Health Study, China | 64 191 women | 896/63 295 | 40-70 | Personal interview FFQ, calculated g/day for fruit and vegetables separately. Defined green leafy vegetables as greens/Chinese greens/spinach. Data divided into fifths. Calculated hazard ratio | BMI, WHR, age, level of education, smoking status, alcohol use, hypertension, disease history, hormone use, occupational history, physical activity | 4.6 | Confirmed by ADA criteria | Fruit: 4.56 v 0.82. Vegetables: 4.04 v 1.15. Green leafy vegetables: 1.28 v 0.26 | 4 |
| Bazzano et al 2008,37 Nurses Health Study USA (1984 onwards) | 71 346 women | 4529/66 817 | 30-55 | Self completed FFQ. Calculated servings/day of fruit, vegetables and combined. Defined green leafy vegetables as spinach/kale/lettuce. Data divided into fifths. Calculated hazard ratio | BMI, physical activity, smoking status, alcohol use, hormone therapy, family history, hypertension, cholesterol | 18 | Confirmed if met WHO criteria (before 1997) or ADA criteria (after 1998) | Fruit: 2.5 v 0.5. Vegetables: 5.2 v 1.5. Fruit and vegetables: 7.5 v 2.1. Green leafy vegetable: data not given | 4 |
| Montonen et al 2005,38 Finnish Mobile Clinic Health Examination Survey | 4304 men and women | 383/3921 | 40-69 | Dietary history interview. Calculated g/day for fruit and vegetables separately. Gave no definition for green leafy vegetables. Data divided into quarters. Calculated relative risks | Occupation, illness, medication, health status, smoking status, blood pressure | 23 | Confirmed via social insurance institutions register | Fruit: >1.47 v <0.31. Vegetables: >1.23 v <0.4. Green leafy vegetables: >0.4 v <0.1 | 3 |
| Liu et al 2004,39 Women’s Health Study, USA | 38 018 women | 1614/36 404 | ≥45 | Self completed FFQ. Calculated servings/day for fruit, vegetables and combined. Defined green leafy vegetables as spinach/kale/lettuce. Data divided into fifths. Calculated relative risks | BMI, smoking status, alcohol use, exercise, family history, menopausal state, vitamin use, blood pressure, cholesterol | 8.8 | Based on self reported | Fruit: 3.91 v 0.62. Vegetables: 6.84 v 1.47. Fruit and vegetables: 10.16 v 2.54. Green leafy vegetables: 1.42 v 0.14 | 3 |
| Ford et al 2001,40 NHANES, USA | 9665 men and women | 1018/8647 | 25-74 | Single 24 hour recall. Calculated servings/week for fruit and vegetables combined. Data divided into thirds. Calculated hazard ratios | BMI, age, ethnicity smoking, blood pressure, hypertension medication, cholesterol, exercise, alcohol, education | 20 | Confirmed either by self report or hospital records | Fruit and vegetables: >5 v 0 | 1 |
| Meyer et al 2000,41 Iowa Women’s Health Study, USA | 35 988 women | 1141/34 847 | 55-69 | Self completed FFQ. Calculated servings/day for fruit, vegetables, and combined. Data divided into fifths. Calculated hazard ratios | BMI, WHR, age, level of education, physical activity, smoking habits, alcohol intake, medication use, | 6 | Based on self reported | Fruit: 3.36 v 0.57. Vegetables: 5.93 v 1.57. Fruit and vegetables: 8.86 v 2.57 | 2 |
FFQ=food frequency questionnaire, BMI=body mass index, WHR=weight:height ratio, ADA=American Diabetes Association.