Abstract Body (Do not enter title and authors here): Introduction: Recent studies have linked niacin metabolism with vascular inflammation and cardiovascular disease (CVD); however, the association is still inconclusive regarding dietary intake, and the findings may not be generalizable to various populations. In this longitudinal study within a Middle Eastern population, we aimed to assess the relationship between dietary intake of B vitamins, including niacin, and the risk of CVD mortality.

Methods: Our study utilized data from the Golestan Cohort Study, which has tracked 50,045 participants aged 40-75 years since 2004. We excluded subjects who reported extreme total energy intake or had a positive history of cancer, CVD, or diabetes at baseline. Vitamin B intake estimations including thiamin, riboflavin, niacin, pyridoxamine, folate, and cobalamin intake were derived from the baseline food frequency questionnaire, noting that supplement use was uncommon in this cohort. To adjust for calorie intakes, we employed the nutrient density method. Cox proportional hazard models were used to calculate hazard ratios (HR) and 95% confidence intervals (CI) for cardiovascular mortality, using the lowest quintile of intake as the reference group for vitamins and adjusting for potential confounders.

Results: We analyzed 42,456 subjects with a mean age of 51.5 ± 8.7 years at baseline. During 579,339 person-years of follow-up (median: 14.1 years), 3,065 CVD deaths were recorded. The median dietary intake of niacin was 25.3 mg/d (Recommended Dietary Allowance = 14-16 mg/d). We observed significant associations between niacin intake (HR_{Q5 vs. Q1} = 1.13, 95% CI = 1.01-1.26, P_trend<0.05) and CVD mortality. When niacin was modeled as a continuous linear variable, it was associated with a greater risk of CVD mortality (HR = 1.05, 95% CI = 1.01-1.09) per 2 mg/1000Kcal/d increase. None of the other B vitamin intakes evaluated were associated with CVD mortality in this population.

Conclusion: These findings suggest that among B vitamins, only dietary niacin intake was positively associated with CVD mortality. Further confirmation in larger studies is needed.