Background: Long COVID (LC) has been associated with persistent inflammation and endothelial dysfunction. Dietary components, particularly vitamins, are involved in inflammation, oxidative stress, and vascular homeostasis, and may influence arterial stiffness in this population. However, the relationship between dietary vitamin intake and vascular stiffness parameters in patients with LC remains poorly understood. Objective: To analyze the association between dietary vitamin intake and central and peripheral arterial stiffness, evaluated by carotid-femoral pulse wave velocity (cfPWV) and brachial-ankle pulse wave velocity (baPWV), in patients with LC. Methods: We conducted a cross-sectional study that included 304 patients with LC. Dietary vitamin intake was assessed using a validated 7-day dietary record (EVIDENT tool). Vascular assessment included cfPWV and baPWV, measured using validated devices (SphygmoCor® and VaSera®). Multiple linear regression analyses were performed to evaluate the associations between vitamin intake and vascular parameters. Model 1 was adjusted for age and sex, while Model 2 additionally included the number of metabolic syndrome components, the SF-36 general health domain, and adherence to the Mediterranean diet. Correction for multiple comparisons was performed using the Benjamini-Hochberg procedure across 36 vitamin-outcome-model contrasts. Results: The mean age was 52.78 ± 11.91 years, and 207 participants were women (68.1%); men were older than women (p = 0.004). In multiple regression analysis, inverse estimates for vitamin B1 intake with cfPWV were observed in both Model 1 (β = -0.568; 95% CI: -1.016 to -0.119; p = 0.014) and Model 2 (β = -0.491; 95% CI: -0.923 to -0.059; p = 0.027). Vitamin B6 intake showed a similar pattern with cfPWV in Model 1 (β = -0.312; 95% CI: -0.606 to -0.018; p = 0.039) and Model 2 (β = -0.302; 95% CI: -0.586 to -0.018; p = 0.038). Vitamin B2 showed inverse but non-significant associations with cfPWV. No significant associations were observed between vitamin intake and baPWV. After FDR correction, no vitamin-arterial stiffness association remained statistically significant; the FDR-adjusted q-value for the B1/B6-cfPWV estimates was 0.347. Conclusions: In this exploratory cross-sectional study, habitual food-based vitamin intake was not significantly associated with central or peripheral arterial stiffness after correction for multiple comparisons. Vitamins B1 and B6 showed inverse nominal estimates with cfPWV; however, these estimates did not survive FDR correction and were not reproduced for baPWV. Longitudinal studies incorporating biochemical micronutrient markers, medication and supplementation data, inflammatory and homocysteine-related biomarkers, and repeated vascular assessment are needed to clarify whether vitamin status is related to vascular health among individuals with persistent post-COVID-19 symptoms.
