Dietary supplement use and regression from prediabetes to normoglycemia: insights from a population-based cohort...

This study aimed to investigate the association between dietary supplement use and regression from pre-diabetes (Pre-DM) to normal glucose regulation (NGR) in a well-characterized population-based cohort.

A total of 2,174 adults with Pre-DM (mean age 51.9 ± 14.2 y; 48.6% men) were enrolled from the Tehran Lipid and Glucose Study (2009-2011) and followed up to 2015-2018. Baseline dietary supplement use was assessed via structured interviewer-administered questionnaires and verified when possible with supplement containers, medication lists, or written records. Participants reporting any supplement, including vitamins and minerals, were classified as users. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for regression to NGR. The overall mean fasting serum glucose (FSG) and 2-hour serum glucose (2 h-SG) levels over time were compared between supplement users and non-users using repeated measures analysis of variance (ANOVA).

Over a median of 6 years of follow-up, 44.2% of participants regressed to NGR. Calcium supplementation was associated with a 25% lower probability of regression (HR = 0.75, 95% CI = 0.59-0.96). Iron supplementation was associated with a 45% higher likelihood of regression to NGR (HR = 1.45, 95% CI = 1.05-2.02). Participants who reported taking iron supplements had a significantly lower mean FSG compared with non-users (99.7 vs. 104 mg/dL, P = 0.003), while mean 2 h-SG concentrations were slightly lower in this group (133 vs. 139 mg/dL, P = 0.09).

Use of iron supplement may increase, whereas use of Ca supplement may decrease the likelihood of regression from Pre-DM to NGR.