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 Do Not Prevent Production of Sufficient Vitamin D

Marks et al.[19] undertook the first longitudinal study relating to this topic by conducting a randomized double-blind controlled trial involving 113 subjects, aged 40 years and above, in Melbourne over the early spring to the early autumn. Half of the volunteers applied sunscreen, SPF 17, to the head, neck, forearms and dorsum of the hand at least once per day starting in the morning. Instructions were given regarding the correct application of the cream. The other half of the volunteers applied placebo cream. Each individual, as wished, could wear hats and clothing, and avoid the sun around midday. Personal sun-badges, used in the final week of the study, demonstrated that the sunscreen and the control groups were exposed to similar doses of sunlight. Blood samples were collected at the beginning and end of the study and analysed for 25(OH)D and 1,25(OH)D. The concentration of 25(OH)D rose in both groups by a similar amount, and age, sex and skin phototype made no difference to the extent of the increase. Thus sunscreen usage could not be interpreted as a risk factor for vitamin D deficiency.[20] The concentration of 1,25(OH)D increased in the control group only, a difference which could not be explained by Marks et al.[19] although it was noted that the mean 1,25(OH)D levels remained in the upper half of the reference range during the entire period of the study in both groups and that no subject was outside the reference range at any time. Sunscreen use prevented the development of solar keratoses, the likely precursors of squamous cell carcinomas (SCCs). Marks et al.[19] concluded that sufficient exposure to the sun is achieved during the Australian summer to allow adequate vitamin D production in subjects who regularly apply sunscreens.

Farrerons et al.[21] followed 24 elderly sunscreen users (mean age 71 years) and 19 controls on five occasions throughout a period of 24 months. Serum 25(OH)D and 1,25(OH)D levels were measured together with several bone markers and parathyroid hormone. All subjects were vitamin D sufficient at the start. The individuals in the sunscreen group were instructed to apply the cream (SPF 15) each morning to sun-exposed parts of the body in the spring and summer months, to avoid sun exposure around noon and to wear adequate clothing. The 1,25(OH)D levels did not change significantly in either the sunscreen or the control groups with the season of the year. The values of 25(OH)D decreased in the winter by 31–35% in the controls and by 17–40% in the sunscreen users. In the summer the serum 25(OH)D levels increased a little more (by 55% and 24% in the 2 years) in the controls than in the sunscreen users (by 35% and 33% in the 2 years). Most importantly, no secondary hyperthyroidism developed in the winter months and no increase in the bone markers was detected in either group. In a follow-up report[22] the bone mass of a subset from each group was evaluated over the 24-month period. No seasonal change in bone mass was observed and no significant difference in this parameter between the sunscreen and control groups occurred throughout the 24 months. It was concluded that sunscreen protection did not increase the risk of osteoporosis in elderly women. These studies were carried out in Barcelona (41°N) where solar UVR is high and the authors speculate that the sunscreen may not have been applied adequately or not to all the sun-exposed body areas.

In an examination of 381 volunteers aged 65 years and above, resident in Boston, Massachusetts, to determine why greater adiposity is associated with lower blood levels of vitamin D3 and 25(OH)D, sunscreen usage was included in a questionnaire exploring sun exposure habits over a 3-month period.[23] The percentage of body fat did not differ with sunscreen use. While hours spent outside and percentage of skin exposed were significantly and positively associated with serum 25(OH)D levels, this was not found for sunscreen use. Another study measured the impact of various lifestyle factors including sun exposure, sunscreen use, dietary and supplemental vitamin D intake and medical history, on 25(OH)D status in older adults (60–91 years).[24] Sunscreen use was shown to be positively correlated with serum 25(OH)D levels. One explanation for this relationship is provided by Thieden et al.[17] who demonstrated that sunscreens are used particularly as a means of avoiding sunburn on days of sunbathing with the intention to tan.

Kimlin et al.[25] assessed serum 25(OH)D status in 124 healthy adults, aged 18–87 years, living in Queensland at the end of the winter months to find out whether some phenotypic characteristics and sun behaviour patterns were important determinants. The participants completed a questionnaire covering the previous month which included the use of sunscreens, their SPF and the body site of application. Although the association between sunscreen use and 25(OH)D levels was not statistically significant, the mean 25(OH)D level increased with increasing frequency of sunscreen use, and the participants who regularly used sunscreens not only had sufficient 25(OH)D levels but also some of the highest concentrations. These findings contrasted with other sun-protective measures, such as wearing long-sleeved shirts or long trousers, where lower 25(OH)D levels tended to be seen. Similar results were revealed in a study of photoprotective behaviour in Irish patients with cutaneous lupus erythematosus.[26] Decreased 25(OH)D levels were only very weakly correlated with sunscreen usage but strongly correlated with sun avoidance by wearing protective clothing and limiting outdoor exposure.

In summary, the evidence described above demonstrates that, in real-life situations, the regular use of sunscreens is unlikely to affect vitamin D status adversely and, indeed, may even enhance it.

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