Table II.
Intervention studies using sun exposure as a source for vitamin D
| Country/latitude | Type of study | Group | Duration | Time | Change in 25(OH)D status/baseline and end-line | Conclusion | Risk of bias analysis |
|---|---|---|---|---|---|---|---|
| Al Ain, UAE, 34.0° N26 | Pilot parallel group trial | RCT, 8 women | Four weeks | 15 min, face, arms and hands | Mean increase of 5.4 nmol/l | Deficiency related to sun exposure behaviours and supplements | Pilot study |
| Sydney, Australia, 33.87° S27 | Cluster RCT | 602 elderly aged 70 or more from 51 aged care facilities | 12 months | 30-40 min/day, early morning, with or without calcium | Increment of 5.9 nmol/l in status. Risk of falls decreased with increase in number of sun exposure sessions attended (IRR, 0.52; 95% CI, 0.31-0.88; P=0.01) | Sun exposure strategy is in effective most likely due to poor adherence to intervention | Concerns with respect to start and adherence to intervention, missing outcome data |
| Abu Dhabi, UAE, 24° N30 | Pilot parallel group trial, Natural sun exposure | 20 female students | 12 wk | Face, arms and hands for 60 min per week | Mean increment of 3.6 nmol/l compared to a drop in control group | Sunlight exposure could be an effective way to improve the vitamin D status among females | Pilot study |
| Delhi, India, 28.61° N28 | Parallel group trial | 36 boys, 35 girls | Four weeks | 30 min between 11:15 and 11:45 AM in summer | Increase of 0.6 nmol/l | Significant increase in serum 25(OH)D | Risk with respect to deviation from intended intervention, selection of reported result |
| Delhi, India, 28.61° N31 | Pre-post trial | School children aged 10-15 yr 50 boys and 155 girls | Four weeks in winter | 30 min/day with 10 per cent exposure between 11:00 AM and 12 noon in winter | Decrease of 0.48 nmol/l predominant decrease in girls | Supplementation required in winter | Elements of RCT missing for RoB analysis |
| Pune, India, 18.52° N29 | Prospective, randomized (1:1), open-label, parallel group | Adult men 40-60 yr | Six months | 20 min daily on face and forearms between 11:00 AM and 3:00 PM over and above current exposure | Mean increment of 13.9 nmol/l | Significant increment in 25(OH)D with exposure between June and December | Concerns with respect to missing outcome data and measurement of outcome data |
RoB, risk of bias; RCT, randomized controlled trials; IRR, incidence rate ratio; CI, confidence interval; 25(OH)D, 25-hydroxy vitamin D