Sunscreens can prevent skin cancer; however, concerns remain that they may increase the risk of vitamin D deficiency.

Neale et al, thus reviewed the literature to investigate associations between sunscreen use and vitamin D3 or 25 hydroxyvitamin D [25(OH)D] concentration by following the Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines. 

They included four experimental studies, three field trials (two randomized controlled trials), and 69 observational studies for their review. Experimental studies showed that sunscreen use much reduced the vitamin D3 or 25(OH)D production induced by exposure to artificially generated ultraviolet radiation; however, the randomized controlled field trials concluded no effect of daily sunscreen application, but the sunscreens used showed moderate protection (sun protection factor [SPF] ~16). The observational studies majorly found no association or that self-reported sunscreen use was related to higher 25(OH)D concentration.

Hence, it is clear that only a little evidence points out that sunscreen decreases 25(OH)D concentration when used in real-life settings, suggesting that apprehensions about vitamin D should not deny skin cancer prevention advice.

Source: Neale RE, Khan SR, Lucas RM, et al. The effect of sunscreen on vitamin D: a review. Br J Dermatol. 2019;181(5):907-15.