Effect of structured, diet-focused educational intervention on knowledge, attitude, and practice related to vitamin D among medical science students: a randomized controlled trial

Abstract Introduction Vitamin D deficiency is a major public health problem worldwide, with a particularly high incidence among university students in the Middle East and Iran. Despite adequate general knowledge, there are still significant gaps in knowledge and practice in the field of vitamin D nutrition among medical science students. This study evaluated the effectiveness of a structured dietary education intervention on knowledge, attitudes, and practice (KAP) related to vitamin D in Northwestern Iran as part of a larger registry study that also assessed biochemical and academic outcomes (reported separately). Methodology A parallel, participant- and outcome assessor-blinded, randomized controlled trial, with participants and outcome assessors blinded to group allocation, with pre- and post-intervention evaluation was conducted in 132 medical science students at Khoy University of Medical Sciences, West Azerbaijan, Iran, who were randomly assigned to an intervention ( n = 66) or control ( n = 66) group by stratified block randomization with allocation concealed in sequentially numbered, sealed, opaque envelopes. Participants in the intervention group received four structured 60-minute sessions over four consecutive weeks that combined foundational content on vitamin D physiology and sun exposure with a primary focus on dietary sources and culinary strategies for increasing vitamin D intake. To preserve blinding, control-group participants received an equal number and duration of sessions on general health topics unrelated to vitamin D, calcium, delivered by the same facilitators in the same format. Vitamin D-related KAP was assessed at baseline and three months post-intervention using the validated D-KAP-38 questionnaire. Analysis of covariance (ANCOVA) was used to compare post-intervention scores while controlling for baseline differences. The four subscales were co-primary outcomes; a Bonferroni-adjusted sensitivity analysis (alpha = 0.0125) was added. Results At baseline, participants demonstrated relatively high general knowledge (86.16 ± 15.16%) but substantially lower nutritional knowledge (58.86 ± 22.26%) and practice scores (52.10 ± 7.89%). Following the intervention, the intervention group showed statistically significant within-group improvements in all four D-KAP-38 subscales (mean chang: general knowledge 9.02%, nutritional knowledge 17.88%, attitude 7.39%, and self-reported practice 7.84%; all p < 0.001). whereas the control group improved less ( general knowledge 7.99%, attitude 4.73%, self-reported practice 3.11%) and showed no change in nutritional knowledge (1.52%, p = 0.716). ANCOVA confirmed significant between-group differences for all subscales after adjustment for baseline scores ( adjusted mean difference, 95% CI: general knowledge 8.30, 5.79–10.80; nutritional knowledge 20.62, 14.82–26.43; attitude 9.66, 6.53–12.79; self-reported practice 7.80, 5.19–10.40; all p < 0.001, partial η² = 0.214–0.277). All four effects remained significant after Bonferroni adjustment (adjusted p < 0.001). Conclusion A four-session, diet-focused educational intervention significantly improved self-reported vitamin D-related knowledge, attitudes, and practice among medical science students in Northwestern Iran, with the greatest gain in nutritional knowledge—historically the weakest component of vitamin D literacy. Because outcomes reported here are knowledge- and self-report-based, they should be interpreted as evidence of improved KAP. Whether these increases are consistent with improved biochemical vitamin D status will be investigated in the companion report of the same trial. These findings should be interpreted cautiously because of retrospective trial registration, exclusive reliance on self-reported outcomes, the absence of multiplicity adjustment in the primary analysis ( a Bonferroni sensitivity analysis is reported), and a near-celing general-knowledge score. Trial registration Iranian Registry of Clinical Trials (IRCT20260612069757N1), registered retroactively on August 6, 2026.