BackgroundMost of the organism’s vitamin D (VD) is obtained through the cutaneous
synthesis after exposure to the sun’s UVB radiation. Sunscreens are
indicated for the prevention of actinic damage to the skin, however, there
are few clinical trials assessing the synthesis of cutaneous VD in real-life
situations of sun exposure with ordinary clothing and usual
photoprotection.ObjectivesTo evaluate the synthesis of VD with suberythemal sun exposure in healthy
adults using topical photoprotection (SPF 30).MethodsQuasi-experimental study, conducted at Rio de Janeiro (Brazil), during
winter, with 95 healthy adults who had 25-OH-VD checked twice, 24 hours
apart, and were exposed to the sun (UVB=20 mJ/cm2), according to a
randomized grouping: SC - use of SPF 30 on the face, neck and chest (n=64),
NO - no sunscreens (n=10), CO - confined from sun exposure for 24h (n=21).
The groups were matched according to the propensity score related to gender,
age, phototype, body mass index, glycosylated hemoglobin and baseline levels
of VD. The outcome evaluated was the variation (ΔVD) in serum level
of 25-OH-VD (ng/ml) between the groups.ResultsA statistically significant difference was identified between CO and SC
groups [median (p25-p75)]: ΔVD =1.4 (-0.3-3.6) vs. 5.5 (4.8-6.6);
p<0.01. There was no difference between SC and NO groups: 5.4 (3.1-6.1)
vs. 4.1 (2.5-6.0); p=0.17.Study limitationsLaboratory analysis technique (chemiluminescence) with great variability,
loss of food intake standardatization, unbalanced groups.ConclusionsSuberythemal sun exposure with sunscreen (SPF 30) provides similar vitamin D
serum variation than without photoprotection in healthy adults.