In Ireland, vitamin D supplementation is recommended for infants⁽¹⁾, 1–5-year-olds⁽²⁾ and older adults⁽³⁾, while recommendations for 5–65-year-olds are being developed. Food supplements placed on the Irish market must be notified to the Food Safety Authority of Ireland (FSAI)⁽⁴⁾ who provide guidance on maximum safe levels (MSL) of micronutrients⁽⁵⁾. Despite the promotion of high-dose vitamin D supplements to protect against COVID-19 during the pandemic, no evidence exists underpinning this⁽⁶⁾. This study aims to assess the trend in vitamin D-containing supplements notified before and during the pandemic. Vitamin D-containing food supplements notified to FSAI between 4^th January 2017 and 30^th December 2021 were identified and assessed in terms of numbers notified before (i.e., 2017–2019) and during (i.e., 2020–2021) the pandemic and amounts of vitamin D provided. In addition, the number of supplements exceeding the adult tolerable upper level (UL; 100 μg) and adult MSL (75 μg), those targeting young children (1–3 years), units of vitamin D used and whether the supplement was a vitamin D-only or a multivitamin/mineral product, were examined.

SPSS (version 25) was used to carry out descriptive analysis, while trend analysis was assessed using ANOVA.A total of 2689 vitamin D-containing food supplements were identified. There was a significant increase in the number of vitamin D-containing supplements notified during the pandemic (1373 in 2020–2021 vs. 1316 in 2017–2019, P < 0.001). When the supplements were grouped into those notified before and during the pandemic, a significant increase in the mean amount of vitamin D provided by those notified during the pandemic was observed (19 μg in 2021–2020 vs. 11 μg in 2017–2019, P < 0.001). This reflected a year-on- year upward trend in the mean amount of vitamin D provided (11 μg in 2017–2019 vs. 16 μg in 2020 vs. 21 μg in 2021, P < 0.001). Of the 2689 vitamin D-containing supplements, <1% (n9) were above the UL and 3% (n80) were above the MSL, the majority of which were notified during the pandemic (n3 in 2017–2019 vs. n6 in 2020–2021 above the UL; n18 in 2017–2019 vs. n62 in 2020–2021 above the MSL). Only 2% (n45) of the total notified supplements were targeted specifically at young children, with none of those supplements exceeding the UL for that age group (50 μg). The majority of notified vitamin D-containing supplements were in multivitamin/mineral form (94%). Many supplement products failed to provide vitamin D amounts in units used in the EU. In conclusion, the number of notified vitamin D-containing supplements, and the amount of vitamin D provided, during the COVID-19 pandemic has increased significantly. Of concern are the supplements that provide vitamin D above the MSL guidance in Ireland and the UL.