Mild Vitamin C Deficiency Is Common in the Inpatient Psychiatric Setting.

Objective: Mild vitamin C deficiency is a psychiatrically relevant nutritional state, with symptoms including apathy, fatigue, and low mood. Although complete vitamin C deficiency has largely been eradicated, mild deficiency remains common in certain populations. Here, we aimed to identify the prevalence of mild vitamin C deficiency in the inpatient psychiatric setting. Methods: We identified 221 patients with plasma vitamin C levels collected on an inpatient psychiatric unit serving a metropolitan area between January 1, 2015, and March 7, 2022. We identified demographic (age, sex, race, housing status, Area Deprivation Index [an index of neighborhood disadvantage]), substance use (tobacco use, alcohol use), diagnostic (depressive, bipolar, psychotic, anxiety, substance use, catatonia, neurocognitive, autism spectrum), and micronutrient (folate, vitamin B12, vitamin D) risk factors. DSM-5-TR was used as the diagnostic system. Bayesian log-normal regressions were constructed to predict vitamin C as a function of these risk factors. We used these same models to predict vitamin C as a function of significant risk factors. Results: We found that 64% (141 of 221; 95% confidence interval 57%-70%) of patients met criteria for mild vitamin C deficiency. While we did not identify robust demographic, substance use, or diagnostic-based risk factors, we found that folate and vitamin D strongly predicted vitamin C levels. To test the utility of these predictors, we simulated vitamin C as a function of folate and vitamin D and found that predicted deficiency remained high (∼ 50%-55%), even when folate/vitamin D were sufficiently replete. Conclusions: We find that vitamin C deficiency is highly prevalent in the inpatient psychiatric setting and remains high even when the relevant risk factor profile is favorable.