Vitamin D Supplementation During COVID-19 Lockdown and After 20 Months: Follow-Up Study on Slovenian Women Aged Between 44 and 66.

INTRODUCTION: The main objective was to assess the impact of the COVID-19 pandemic on vitamin D supplementation habits and their changes in the follow-up, 20 months after the study in Slovenian premenopausal and postmenopausal women.

METHODS: A cross-sectional study was conducted between March and May 2021. 176 healthy women aged 44 to 65 from the Central Slovenian region were included in the final analysis. Vitamin D status was determined by measuring 25(OH)D concentration. After 20 months an online follow-up questionnaire was sent out, to which 123 participants responded with complete data.

RESULTS: Between March and May 2021, 61% of the participants were supplementing vitamin D. 55% of the supplementers and 88% of the non-supplementers had insufficient levels (total 25(OH)D <75 nmol/L). After 20 months in the follow-up, it was found that 62% of participants were taking vitamin D supplements, but only 70% of those who had initially reported taking supplements were still doing so. In the follow-up 61% of participants stated that they started or increased vitamin D intake due to COVID-19.

CONCLUSIONS: Vitamin D supplementation increased 7-fold compared to pre-pandemic levels and remained at a high level after 20 months. However, a significant number of participants discontinued supplementation, and only one-fifth were taking vitamin D throughout the entire year. Supplementation is effective for vitamin D deficiency prevention only at the individual level, however due to low compliance it should not be the only strategy for preventing vitamin D deficiency in the population.