Intense Testing and Use of Vitamin D Supplements Leads to Slow Improvement in Vitamin D Adequacy Rates: A Cross-Sectional Analysis of Real-World Data.

Background: Vitamin D testing (VDT) and supplement use (VDS) are on the rise, but most patients remain deficient (<30 ng/mL-VDD). We designed the present real-world study to assess this paradox.

Methods: We reviewed data from all patients visiting our clinics between 2014 and 2022. We estimated the rate of patients with vitamin D adequacy (≥30 ng/mL) (VDA) by year and month of testing, the dose of VDS (low (≤1200 IU/day), medium (1201-3000 I/day) and high dose (>3000 IU/day)), intake duration (short-term (<12 months) and long-term use (≥12 months)), and timing of use (current use, former use, no use).

Results: We enrolled n = 6912 subjects with vitamin D measurements: n = 5195 females (75.2%), age 44.0 ± 16.8 years, BMI 27.9 ± 6.5 kg/m; never users: n = 5553 (80.3%), former users: n = 533 (7.7%), current users: n = 826 (12.0%). Current use of VDS was higher in females. VDT rose from 42.1% in 2014 to 92.7% in 2022, and VDA rose from 14.8% to 25.5% for the same time. VDA was found overall in n = 1511 (21.9%); Never users: n = 864 (15.6%), Former users: n = 123 (23.2%); and Current users: n = 370 (44.8%). The maximal VDA (67.9%) was found in subjects using high-dose VDS in the long term.

Conclusions: Despite the significant rise in VDT and VDS use, VDA was found in a minority of patients. Prolonged use of high-dose supplements produces modest improvements in VDA.