Metabolic syndrome is associated with increased vitamin C requirements in the US National Health and Nutrition Examination Survey

Metabolic syndrome (MetS) comprises a constellation of dysregulated cardiometabolic parameters. This study assessed associations between MetS and vitamin C in the US National Health and Nutrition Examination Survey (NHANES) to determine vitamin C requirements in people with a range of MetS severity, the hypothesis being that people with higher MetS severity would have higher requirements for the vitamin. Data for non-supplementing, fasting adults (n = 4,832) was extracted from NHANES 2003-6 and 2017-18 and included demographic and lifestyle variables, cardiometabolic laboratory variables, vitamin C dietary intakes and serum concentrations. MetS severity score was calculated using sex, waist circumference, systolic blood pressure, HDL cholesterol, triglycerides and fasting glucose concentrations. The mean (range) MetS severity score for the group was 0.19 (-4.0 to 6.8). There was a negative association between MetS severity score and serum vitamin C (r=-0.203, p < 0.001). Participants who met the vitamin C adequacy threshold of ≥50 µmol/L had a mean MetS severity score of 0.00 vs 0.38 in those who did not meet the threshold (p < 0.001). When the group was stratified by MetS severity score tertiles, the participants with the highest scores required an intake >100 mg/d, equating to an additional 65 mg/d (or 2.7-fold higher intake requirement) to meet the adequacy threshold relative to those with the lowest scores. Comparable relationships were observed between the individual MetS severity score components and vitamin C status and requirements. Overall, the results indicate that increased metabolic dysregulation results in decreased vitamin C status and a higher intake requirement for the vitamin to meet adequate circulating concentrations.