Ultra-processed food consumption (NOVA index) and the odds of diabetic nephropathy in women: a case-control study

diabetic nephropathy (DN) is a major complication of diabetes mellitus associated with increased morbidity and mortality. Dietary factors, particularly unhealthy food consumption, may contribute to kidney dysfunction. This study aimed to investigate the association between the NOVA index and the odds of DN in women with type 2 diabetes. In this case–control study, 210 women aged 30–65 years with type 2 diabetes (duration 3–10 years) were recruited from the Kowsar Diabetes Clinic in Semnan, including 105 patients with DN and 105 diabetic controls without DN matched for age and diabetes duration. Dietary intake was assessed using a 147‑item food frequency questionnaire (FFQ), and physical activity was measured by the International Physical Activity Questionnaire (IPAQ). Biochemical variables were extracted from medical records. The NOVA classification was calculated based on dietary intake and categorized into tertiles. Higher NOVA indexs were associated with increased albumin‑to‑creatinine ratio, diastolic blood pressure, and LDL levels, and lower vitamin D3 levels. Participants in the second tertile of NOVA index had significantly higher odds of DN compared with the lowest tertile (OR = 6.03; 95% CI: 2.75–13.22; P < 0.001). Higher consumption of several ultra‑processed food groups—including cakes and pastries, fast foods, processed meats, salty snacks, oils and sauces, and sweets—was significantly associated with increased DN risk. Greater consumption of ultra‑processed foods, as reflected by higher NOVA indexs, was associated with higher odds of DN among women with type 2 diabetes.