Purpose: Although vitamin B6 has been suspected to prevent the progression of diabetic retinopathy, evidence of this in patients with type 2 diabetes based on longitudinal studies is sparse. This study investigated the relationship between vitamin B6 intake and the incidence of diabetic retinopathy in Japanese patients with type 2 diabetes.
Methods: The study was part of an examination of a nationwide cohort of patients with type 2 diabetes aged 40-70 years with HbA1c ≥ 48 mmol/mol. After excluding nonresponders to a dietary survey using the Food Frequency Questionnaire based on food groups, 978 patients were analyzed. Primary outcome was the 8-year risk of a diabetic retinopathy event, and Cox regression analyses estimated hazard ratios (HRs) for retinopathy according to vitamin B6 intake adjusted for age, gender, body mass index, HbA1c, smoking, energy intake, and other confounders.
Results: Mean vitamin B6 intake in quartiles ranged from 1.1 to 1.6 mg/day, and half of the participants had vitamin B6 intake below the recommended daily dietary allowance according to dietary reference intakes in Japanese adults (men 1.4 mg/day; women 1.2 mg/day). After adjusting for confounders, HRs for diabetic retinopathy in the 2nd, 3rd, and 4th quartile groups of vitamin B6 intake compared with the 1st quartile group were 1.17 (95% confidence interval 0.81-1.69, p = 0.403), 0.88 (0.58-1.34, p = 0.550), and 0.50 (0.30-0.85, p = 0.010), respectively.
Conclusions: Findings suggested that high vitamin B6 intake was associated with a lower incidence of diabetic retinopathy in Japanese with type 2 diabetes.
Keywords: Diabetic retinopathy; Medical nutrition therapy; Type 2 diabetes; Vitamin B6 intake.