Impact of Sunscreens on Vitamin D
J F. Nash, Ph.D.1; Zahid Javaid, Pharm.D.2 ; Paul Tanner, B.S.1; Darrell Rigel, M.D.3 ;
1The Procter & Gamble Company, 2University of Cincinnati, 3New York University Medical Center
Repeated exposure to solar ultraviolet (UV) radiation is known to produce deleterious effects on human skin include-ing skin cancers and photoaging. Health-care providers including the AAD have advocated a "safe sun strategy" to reduce sunlight exposure and resultant acute and chronic skin damage. A part of this strategy is the daily use of sun-screens with a minimum SPF 15. It has been suggested that limiting exposure to solar light may have negative consequences. Specifically, protecting against sunlight exposure may significantly reduce the production of vitamin D (Vit. D) by skin increasing the risk of Vit. D de-ficiency leading to negative health effects.
The objectives of this analysis were to:
- estimate the production of Vit. D based on measures of sunlight exposure; and
- determine the impact of an SPF 15 sunscreen on Vit. D levels in humans.
A total of 92 female subjects from 5 locations, New York City, NY (n=15); Vail, CO (n=17); Plantation, FL (n=20), La Jolla, CA (n=18) and Chicago, IL (n=22), age 30-45 years, were recruited for this study. Following enrollment, the investigator or designated technician at each site discussed details of the study with each participant, including the accurate documentation of time spent in sunlight during January 4-10 (IL) and March 1-7 (all other sites). Each subject was provided a diary in which activities were recorded every 30 min throughout the day for 7 days. Subjects documented their outdoor activities and whether they were exposed to sunlight. At the end of the study, the diaries were returned to the investigator. Each investigator measured the erythemally weighed flux (mW/cm2) of sunlight. This value, together with the sunlight exposure (min), was used to calculate the daily dose of UV (mJ/cm2). The estimated amount of Vit. D synthesized was based on the formula of Holick (2001)1 in which 1 MED of whole body exposure to sunlight is equivalent to 10,000 IU of Vit. D.
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In 5 geographies during the winter months, the average daily exposure to sunlight ranged from 29 to 70 min. Using the most conservative assumptions, the estimated synthesis of Vit. D was equivalent to half the AI (approximately 100 IU) even if an SPF 15 sunscreen was applied at the proper dose (2 mg/cm2) during the coldest month of the year. The combination of diet2 and sunlight even with daily use of an SPF 15 sunscreen provide the AI for Vit. D. This is consistent with population-based studies in which strict photoprotection practices had no impact on Vit. D levels3-6.
The benefits of a "safe sun strategy" outweigh concerns associated with diminished exposure to solar UV, i.e., Vit. D deficits.
References:1Holick (2001) The Lancet 357:4-6; 2Moore et al. (2004) J Am Diet Assoc. 104:980-83; 3Farreons et al. (1998) Br J Dermatol 139:422-27; 4Marks et al. (1995) Arch Dermatol 131:415-21; 5Sollitto et al. (1997) J Am Acad Dermatol. 37:942-7; 6Weinstock et al. (1992) J Invest Dermatol. 98:809-11.