Prevalence and correlates of high red blood cell folate concentrations in the Canadian population using three proposed cut-points

Introduction: A distinct shift towards higher folate concentrations has emerged in Canada. These higher concentrations have known benefits, including neural tube defect prevention, but concerns have been raised regarding potential associations with adverse health outcomes. The aim of this research was to propose cut-offs for high RBC folate concentrations and identify their correlates. Methods: RBC folate was measured in a nationally representative, cross-sectional sample of Canadians (N=5248), aged 6 to 79 years. RBC folate concentrations were adjusted from Immulite 2000 immunoassay to microbiologic assay. The population was characterized at three RBC folate cut-offs, 1450 nmol/L, 1800 nmol/L and 2150 nmol/L. We used t-tests to examine differences by age, sex, income and body mass index (BMI) at each cut-off and logistic regression to explore associations with folic acid supplement intake. Results: Participants had 16%, 6% and 2% prevalence of having high RBC folate, at thresholds of1450 nmol/L, 1800 nmol/L and 2150 nmol/L, respectively. Females, those aged 60 to 79 years and overweight or obese participants had the greatest prevalence of having high RBC folate at each cut-off. Folic acid supplement users were more likely than non-users to have high RBC folate concentrations. Conclusions: Older age, higher BMI and folic acid supplement use were identified as correlates of high folate status. A high RBC folate concentration cut-off will advance the field towards consistent measurement and reporting of high folate status. This may facilitate future investigation of associations between RBC folate concentrations at the upper end of the distribution and health outcomes.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author