Vitamin D supplement use among UK shift workers: a cross-sectional survey

Vitamin D deficiency is considered to increase risk of musculoskeletal disorders, hinder standing balance and impair immunity (1) . The prevalence of low vitamin D status is endemic among UK night shift workers, exceeding 30% and 45% in men and women, respectively (2) . However, knowledge and attitudes to vitamin D supplementation among shift workers in the UK have not been well captured. This study aimed to examine awareness of vitamin D among UK adult shift workers, and assess current practices related to vitamin D supplementation. An anonymous online cross-sectional survey was developed following the Checklist for Reporting Results of Internet E-Surveys (CHERRIES) (3) and disseminated via social media. Adaptive questioning and branching techniques facilitated the collection of categorical-level data across a maximum of 59 non-compulsory questions, including multiple choice, free text, and Likert scale formats. Responses were captured across a 5-week period between March-April 2025. Data was self-reported. Data analysis involved descriptive statistics and Fisher’s exact test for comparison across groups. In total, 52 shift workers responded to the survey (37% female; 37% male; 1.9% non-binary; 24% gender not disclosed). Most participants reported working an irregular shift pattern (44%), followed by fixed (29%), rotating (21%) or other (6%) shift pattern. Of 45 complete responses, 53% (n=24) reported taking a vitamin D supplement, of which the dose ranged from 5µg/d to >100µg/d. The most commonly reported supplement dose was 25µg/d (25%; n=6/24); 4 participants could not identify the dose of the supplement. Only 42% (n=10/24) of participants reported taking the supplement daily. The higher proportion of vitamin D supplement use in females (67%; n=12/18) compared to males (42%; n=8/19) was not statistically significant (P=0.19). Of those taking a vitamin D supplement, the majority had been taking the supplement for ≥4 months (58%; n=14/24). Few participants (12%; n=5/43) reported changing vitamin D supplement use since starting shift work. Although 65% (n=30/46) reported awareness of potential health benefits of vitamin D, only 2 participants correctly identified 10µg/d as the Recommended Nutrient Intake (RNI) value for vitamin D in the UK. Of 10 participants who reported social media as a source of vitamin D information, 3 reported social media as the only information source. Only 1 (of 43) participant reported receiving guidance on vitamin D within the workplace. Of 21 participants who reported having a previous blood test for nutrition-related concerns, 71% (n=15) reported vitamin D deficiency. Self-reported vitamin D supplement use is common among UK shift workers, but awareness of recommended intake and workplace guidance is limited. Addressing this gap through targeted workplace education could help to ensure safe and effective supplementation practices among UK shift workers, and could potentially improve organisational safety and performance outcomes through reduced musculoskeletal disorders and sickness absence.