Chronic sunscreen use decreases circulating concentrations of 25-hydroxyvitamin D. A preliminary study.

Sunscreens block the absorption of the sunlight spectrum responsible for the cutaneous synthesis of vitamin D (ultraviolet B). The present study was prompted by our observation of suppression of cutaneous vitamin D formation by a single application of sunscreening agents. We measured the index of vitamin D body store, serum 25-hydroxyvitamin D (25-OH-D) level, in 20 long-term users of p-aminobenzoic acid (PABA) and in 20 controls matched by age and exposure to sunlight. Serum 25-OH-D levels were significantly lower among long-term PABA users than among normal controls: 40.2 +/- 3.2 vs 91.3 +/- 6.2 nmol/L. Furthermore, vitamin D deficiency, ie, 25-OH-D levels below 20.0 nmol/L, was seen in two PABA users and in none of the controls. This preliminary study suggests that long-term use of PABA may be associated with low body stores of vitamin D in some persons.