Introduction:
This study sought to use the latest Life's Essential 8 scoring tool to obtain information on the relationship between serum vitamin D concentration and adolescent cardiovascular health (CVH).

Material and methods:
A total of 1,819 teenagers aged 16–19 were enrolled. Associations between serum vitamin D concentrations and CVH ratings were estimated using multiple linear regression and multinomial logistic regression methods, and the dose–response relationship was examined by restricted cubic spline analysis.

Results:
After adjusting for all confounding factors, serum vitamin D concentrations were positively correlated with CVH scores (β=0.12; 95% CI: 0.09-0.14, p<0.001). Among the sex and race subgroups, the correlation was stronger in male, Mexican American and Non-Hispanic Black participants, with ORs of 1.05 (95% CI: 1.03-1.07), 1.06 (95% CI: 1.04-1.08), p=0.002), 1.07 (95% CI: 1.03-1.11), 1.09 (95% CI: 1.05-1.14), p=0.01, 1.04 (95% CI: 1.01-1.06), and 1.05 (95% CI: 1.02-1.09), p=0.01, respectively. Serum vitamin D concentrations had a nonlinear relationship with CVH ratings. CVH scores grew with serum vitamin D concentrations up to the inflection point (86 nmol/L) (β=0.17 (95% CI: 0.135-0.206, p<0.001). When serum vitamin D concentrations exceeded 86 nmol/L, CVH scores were not associated with serum vitamin D concentrations.

Conclusions:
The study identifies a nonlinear relationship between serum vitamin D levels and CVH in US adolescents aged 16-19, with an inflection point at 86 nmol/L. These findings underscore the importance of vitamin D in adolescent cardiovascular health and suggest the need for targeted health strategies, particularly in high-risk groups such as male, Mexican American, and Non-Hispanic Black teenagers.