Exploring the association between serum vitamin D levels and type 2 diabetes risk in US adults

Serum vitamin D levels have been linked to the risk of developing type 2 diabetes (T2D), but findings across studies remain inconsistent.

This study included 9,522 participants with a mean age of 43.55 ± 0.34 years, of whom 52.76% were male, from the 2007-2014 National Health and Nutrition Examination Survey (NHANES) with complete data on serum vitamin D, T2D diagnosis, and relevant covariates. Participants were categorized into three groups based on serum vitamin D levels: sufficient (>75 nmol/L), suboptimal (50-74 nmol/L), and deficient (<50 nmol/L). Restricted cubic spline and multivariable logistic regression models were used to analyze the relationship between serum vitamin D and T2D risk.

After adjusting for confounders (sex, ethnicity, age, BMI, education, marital status, physical activity, alcohol consumption, smoking, PIR, and depressive symptoms), participants in the sufficient (OR = 0.68; 95% CI: 0.53-0.87) had significantly lower T2D risk compared to the deficient group (p for trend = 0.003). The relationship between vitamin D and T2D was non-linear, with the lowest T2D risk occurring at 74.99 nmol/L.

Sufficient serum vitamin D levels are associated with a lower risk of T2D, with the optimal level identified as 74.99 nmol/L. Further randomized controlled trials are needed to confirm these findings.