Does Chronic Sunscreen Use Reduce Vitamin D Production to Insufficient Levels?

M. Norval; H.C. Wulf

Disclosures

The British Journal of Dermatology. 2009;161(4):732-736. 

In This Article

Sunscreens Prevent Production of Sufficient Vitamin D

No randomized controlled trials or longitudinal studies have been reported showing that suncreens significantly suppress cutaneous vitamin D synthesis, but three papers published about 20 years ago provide information that this might be the case. First, Matsuoka et al.[13] applied ethanol or ethanol containing 5%para-aminobenzoic acid (PABA) to pieces of human skin prior to exposure to 30 mJ cm−2 solar-simulated radiation. Without the sunscreen, 15% of the 7-dehydrocholesterol in the basal layer of the epidermis, the site where most is located,[14] was converted to previtamin D3, but this reaction was totally blocked by the sunscreen. Eight white-skinned subjects were then whole-body irradiated with one personal minimum erythemal dose (MED) from Philips TL-12 lamps (emission range 280–350 nm). One hour prior to the exposure, a PABA-based suncreen, SPF 8, was applied to the total body surface of four of the volunteers. The method of application and the amount used were not stated. By day 1 postexposure the vitamin D3 concentration in the serum rose from 1·5 to 25·6 ng mL−1 in the unprotected subjects but remained at the preirradiation level in the sunscreen-protected subjects. Thus the single application of the sunscreen had prevented the production of vitamin D3 although, as each group contained only four individuals, the possibility of statistical uncertainty was high. Serum 25(OH)D levels were not measured.

Secondly, 20 white-skinned patients with a history of skin cancer who, in the previous 12 months had been applying PABA sunscreen (SPF not stated) on sun-exposed parts of the body before going outdoors were compared with 20 healthy controls (members of the same household or neighbours) of similar age who had similar sunlight exposure but did not use sunscreens.[15] Blood samples were collected during the summer. It was found that the mean 25(OH)D level in the sunscreen user group was about half of that in the control group. However, no assays of 25(OH)D were performed before the sunscreen usage started, only a single blood sample from each individual was collected, the regular use of the sunscreen was determined retrospectively by history taking and, most importantly, no method was used to check whether the patients and controls had received similar sunlight exposure over the previous year. Indeed, as all the patients had a past history of skin cancer, it is possible that they would tend to avoid direct sunlight to a greater extent than the controls. In addition, more recent surveys have shown that sunscreen users in general expose themselves more frequently and for longer periods to sunlight than nonsunscreen users.[16,17]

Thirdly, a sunscreen with SPF 15 was applied to different body areas of untanned white subjects (phototype III) 1 h prior to whole-body UVB irradiation (Philips TL-12 lamps) of just under one personal MED.[18] Vitamin D3 levels in the serum were measured before and 24 h after the irradiation, each group consisting of four or five individuals. Sunscreen coverage over the whole body completely blocked the UVB-induced synthesis of vitamin D3, and > 19% of the body needed to be free of sunscreen for a significant rise in serum vitamin D3 to occur. Serum 25(OH)D levels were not measured.

Comments

3090D553-9492-4563-8681-AD288FA52ACE

processing....