THE EFFECT OF REGULAR SUNSCREEN USE ON VITAMIN-D LEVELS IN AN AUSTRALIAN POPULATION - RESULTS OF A RANDOMIZED CONTROLLED TRIAL

Background end Design: Studies published have suggested a possibility that regular use of sunscreen to prevent skin cancer may put the popul ation, particularly elderly people, at risk of vitamin D deficiency. W e aimed to determine whether regular use of sunscreens in the normal a dult population, as recommended by public health authorities for the p revention of skin cancer, may put individuals at risk of vitamin D def iciency. A randomized double-blind control trial of the daily use of a broad-spectrum sunscreen (sun protection factor [SPF] 17) vs placebo cream over a summer period in Australia was conducted in 113 people ag ed 40 years and over, with sampling stratified by age. All participant s had at least one solar keratosis. Serum samples taken at the beginni ng and at the end of the study were analyzed for 25-hydroxyvitamin D-3 and 1,25-dihydroxyvitamin D-3. Results: Mean levels of 25-hydroxyvita min D-3 rose significantly by the same amount in both groups over the period of the study (placebo, +12.8 mmol/L; sunscreen, +11.8 mmol/L). Mean levels of 1,25-dihydroxyvitamin D-3 increased significantly in th e placebo group only (placebo, +10.8 pmol/L; sunscreen, +1.3 pmol/L), but for no subject in either group was the level of 1,25-dihydroxyvita min D-3 outside the reference range either at the start or at the end of the study. There were no significant differences by age, sex, and s kin type in the change in 25-hydroxyvitamin D-3 or 1,25-dihydroxyvitam in D-3 over the study period. Conclusions: No person, including those aged 70 years and over, developed any vitamin D levels outside the nor mal reference range during the period of the study. The data suggest t hat over an Australian summer sufficient sunlight is received, probabl y through both the sunscreen itself and the lack of total skin cover a t all times, to allow adequate vitamin D production in people who are recommended to use sunscreens regularly. More work is required to eluc idate the relationship between 25-hydroxyvitamin D-3 and 1,25-dihydrox yvitamin D-3, particularly during the different seasons of the year.