Background: Antioxidants and dietary fiber are postulated to have preventive effects on diabetic retinopathy, but evidence is lacking. We investigated this association in a cohort with type 2 diabetes 40-70 years of age with hemoglobin (Hb)A1C ≥6.5%, originally part of the Japan Diabetes Complications Study.
Methods: After excluding people who did not respond to a dietary survey and patients with diabetic retinopathy or a major ocular disease at baseline, we analyzed 978 patients. Baseline dietary intake was assessed by a food frequency questionnaire based on food groups and 24-hour dietary records. Primary outcome was incident diabetic retinopathy determined using international severity scales.
Results: Mean fruit intake in quartiles ranged from 23 to 253 g/day, with increasing trends across quartiles of fruit intake for vitamin C, vitamin E, carotene, retinol equivalent, dietary fiber, potassium, and sodium. Mean energy intake ranged from 1644 to 1863 kcal/day, and fat intake was approximately 25%. HbA1C, body mass index, triglycerides, and systolic blood pressure were well controlled. During the 8-year follow-up, the numbers of incident cases of diabetic retinopathy from the first through the fourth quartiles of fruit intake were 83, 74, 69, and 59. Multivariate-adjusted hazard ratios for the second, third, and fourth quartiles of fruit intake compared with the first quartile were 0.66 (95% confidence interval = 0.46-0.92), 0.59 (0.41-0.85), and 0.48 (0.32-0.71) (test for trend, P < 0.01). There was no substantial effect modification by age, sex, HbA1C, diabetes duration, overweight, smoking, and hypertension. Risk for diabetic retinopathy declined with increased intake of fruits and vegetables, vitamin C, and carotene.
Conclusion: Increased fruit intake in ranges commonly consumed was associated with reduced incident diabetic retinopathy among patients adhering to a low-fat energy-restricted diet.