Serum Vitamin D Status, Dietary Calcium Intake and Insulin Resistance among Adults with Prediabetes

Abstract

Background: Prediabetes is characterized by impaired glucose regulation and an increased risk of progression to type 2 diabetes mellitus.

Objective: To evaluate the association of serum vitamin D status and dietary calcium intake with insulin resistance among adults with prediabetes.

Methodology: This prospective cross-sectional study was conducted at three Districts of Sindh i.e. Khairpur Mirs, Tharparkar and Mithi from 1^st April 2025 to 30^th September 2025. Three hundred and twenty five adults with prediabetes were enrolled. Demographic, anthropometric, clinical, biochemical, and dietary data were recorded. Demographic and clinical variables including age, gender, body mass index (BMI), waist circumference, smoking status, physical activity level, blood pressure, family history of diabetes, and relevant medical history were recorded.

Results: The mean age of participants was 48.7±10.2 years, with a mean BMI of 29.1±4.8 kg/m² and waist circumference of 97.6±10.5 cm. The mean fasting plasma glucose was 110.8±8.6 mg/dL, HbA1c was 6.0±0.3%, fasting insulin was 16.9±6.3 µIU/mL, and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) was 4.6±1.8. The mean serum vitamin D level was 22.8±8.7 ng/mL, while the mean dietary calcium intake was 721±198 mg/day. Vitamin D deficiency was present in 132 (40.6%) participants, and 98 (30.2%) consumed less than 600 mg of calcium daily. Participants with vitamin D deficiency had significantly higher (P<0.001) HOMA-IR and fasting insulin levels than those with sufficient vitamin D status (5.3±1.8 vs. 3.6±1.2 and 19.1±5.9 vs. 13.8±4.7 µIU/mL) respectively.

Conclusion: Vitamin D deficiency and inadequate dietary calcium intake were common among adults with prediabetes and were significantly associated with greater insulin resistance and poorer glycemic control.