Folate, Vitamin B(6), and Vitamin B(12) Status in Association With Metabolic Syndrome Incidence

IMPORTANCE: The associations of B vitamin status with metabolic syndrome (MetS) incidence among the US population remain unclear. OBJECTIVE: To investigate intakes and serum concentrations of folate, vitamin B(6), and vitamin B(12) in association with MetS risk in a large US cohort. DESIGN, SETTING, AND PARTICIPANTS: This prospective study included Black and White young adults in the US who were enrolled from 1985 to 1986 and studied until 2015 to 2016. Diet was assessed using a validated diet history at examination years 0, 7, and 20. Serum concentrations of folate, vitamin B(6), and vitamin B(12) were assayed at examination years 0, 7, and 15 in a subset of 1430 participants. MetS was ascertained by clinic and laboratory measurements and self-reported medication use. Data were analyzed between January and July 2021. EXPOSURES: Intakes and serum levels of folate, vitamin B(6), and vitamin B(12). MAIN OUTCOMES AND MEASURES: Multivariable Cox proportional hazards regression models were used to calculate hazard ratios (HRs) and 95% CIs for the associations of energy-adjusted B vitamin intakes or serum B vitamin levels with incident MetS. RESULTS: The study included 4414 participants, with 2225 Black individuals (50.4%) and 2331 women (52.8%). The mean (SD) age at baseline was 24.9 (3.6) years. A total of 1240 incident MetS cases occurred during the 30 years (mean [SD], 22.1 [9.5] years) of follow-up. Compared with the lowest quintile of each energy-adjusted B vitamin intake, the HRs for incident MetS in the highest quintile were 0.39 (95% CI, 0.31-0.49) for folate (P for trend < .001), 0.61 (95% CI, 0.46-0.81) for vitamin B(6) (P for trend = .002), and 0.74 (95% CI, 0.58-0.95) for vitamin B(12) (P for trend = .008) after adjustment for potential confounders. Similarly, significant inverse associations were observed in the subset with serum data on these B vitamins (folate: HR, 0.23; 95% CI, 0.17-0.33; P for trend < .001; vitamin B(6): HR, 0.48; 95% CI, 0.34-0.67; P for trend < .001; and vitamin B(12): HR, 0.70; 95% CI, 0.51-0.96; P for trend = .01). CONCLUSIONS AND RELEVANCE: This prospective cohort study found that intakes and serum concentrations of folate, vitamin B(6), and vitamin B(12) were inversely associated with incident MetS among Black and White young adults in the US.