Dietary Vitamin K Intake and Insulin Resistance: Implications for Early Diabetes Risk in U.S. Adults (NHANES 2001-2018)

Background: Vitamin K (VK) has emerging roles beyond coagulation, including potential involvement in glucose metabolism. While large cohorts report inverse associations between VK status and incident type 2 diabetes, less is known about its relation-ship with insulin resistance in general populations. Methods: We conducted a cross-sectional analysis of 23,247 adults from the National Health and Nutrition Examination Survey (NHANES) 2001-2018. Dietary VK intake was assessed using a 24-h recall and modeled as energy-adjusted nutrient density (µg/1000 kcal). Fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), fasting glucose, and HbA1c were analyzed using survey-weighted linear regression; models were adjusted for demographic, socioeconomic, lifestyle, and adiposi-ty-related factors. Effect modification by baseline metabolic status was evaluated, and sensitivity analyses assessed robustness. Results: Higher energy-adjusted VK intake was independently associated with lower fasting insulin and HOMA-IR, but not with fasting glucose or HbA1c. Each SD increase in VK intake was associated with 1.4% lower fasting insulin (95% CI -2.4% to -0.4%) and 1.3% lower HOMA-IR (95% CI -2.3% to -0.3%) in fully adjusted models. Associations were attenuated but remained signif-icant after adjustment for adiposity. Effect modification by baseline metabolic status was observed, with stronger associations among normoglycemic individuals. Findings were robust across sensitivity analyses. Conclusions: In this nationally representative sample of U.S. adults, higher VK intake was modestly associated with lower insulin resistance markers. Dietary VK intake may contribute to maintenance of insulin sensitivity, particularly in metabolically intact states. Prospective studies incorporating comprehensive VK biomarkers and dynamic measures of insulin sensitivity are warrant-ed.