We primarily obtain vitamin D (VD) through cutaneous synthesis after exposure to the sun′s ultraviolet B (UVB) radiation. Sunscreens are known to prevent actinic damage to the skin. However, there are few clinical trials that assess the synthesis of cutaneous VD in real-life scenarios of sun exposure with ordinary clothing and regular photoprotection.

The present study evaluated the synthesis of VD with suberythemal sun exposure in healthy adults using topical photoprotection (SPF 30).

It included 95 healthy adults and checked their 25-OH-VD twice, 24 hours apart and exposed them to the sun (UVB = 20 mJ/cm²), according to the groups: SC - use of SPF 30 on the face, neck and chest, NO - no sunscreens, CO - confined from sun exposure for 24 hours. It matched the groups according to the propensity score related to gender, age, phototype, body mass index, glycosylated hemoglobin and baseline levels of VD. 

The study evaluated the variation (ΔVD) in serum level of 25-OH-VD (ng/mL) between the groups.

It found a statistically significant difference between CO and SC groups and no difference between SC and NO groups.

This study indicates that suberythemal sun exposure with sunscreen (SPF 30) delivers similar VD serum variation than without photoprotection in healthy adults.

Source: Pereira LA, Luz FB, de Oliveira Carneiro CMM, et al. Evaluation of vitamin D plasma levels after mild exposure to the sun with photoprotection. An Bras Dermatol. 2019;94(1):56-61.