ObjectivesKnown as ‘sunshine vitamin’, sun exposure is a major and natural source of vitamin D. This study aimed to investigate the effects of moderate sun exposure and vitamin D supplementation on vitamin D concentration among Malay women in Kelantan, Malaysia. MethodsA quasi-experimental study design was carried out among female indoor workers with vitamin D deficiency (serum 25-hydroxyvitamin D < 50 nmol/l) for 12 weeks to evaluate the effects of moderate sun exposure (n = 19; 15 minutes sun exposure biweekly on face, lower arms, hands and feet), vitamin D supplementation (n = 15; 50 000 IU cholecalciferol weekly) and placebo (n = 15) on serum 25-hydroxyvitamin D (25(OH)D) levels. Data was collected twice from each respondent, firstly during baseline and secondly during endpoint. Body composition measurements (body fat percentage and body mass index), fasting blood test (serum 25(OH)D level) and questionnaire (socio-demographic, physical activity and dietary vitamin D intake) were conducted. The vitamin D classification was based on the 2011 Endocrine Society Clinical Practice Guidelines. Repeated measure ANOVA within group analysis was applied. ResultsThe baseline characteristics did not differ significantly among study groups except for age (F = 6.15, p = 0.004). After 12 weeks, serum 25(OH)D levels increased significantly in sun exposure (mean difference (MD) = 14.27 nmol/l, p < 0.001) and vitamin D supplement group (MD = 14.30 nmol/l, p < 0.001) but not in the placebo group (MD = 1.63 nmol/l, p = 0.067). ConclusionsThe 12-weeks intervention with moderate sun exposure and vitamin D supplementation showed a similar significant increment in serum 25(OH)D levels. However, no changes in serum 25(OH)D was observed in the placebo group. These results showed that sunlight exposure and vitamin D supplement were equally helpful in improving serum 25(OH)D levels in participants with vitamin D deficiency. Funding SourcesShort Term Research Grant, Universiti Sains Malaysia.