Use of sunscreen and vitamin D production.
|Article Type:||Clinical report|
Sunscreens (Cosmetics) (Health aspects)
Alfacalcidol (Physiological aspects)
Calcifediol (Physiological aspects)
Vitamin D (Physiological aspects)
Sun exposure (Health aspects)
|Publication:||Name: Australian Journal of Medical Herbalism Publisher: National Herbalists Association of Australia Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2010 National Herbalists Association of Australia ISSN: 1033-8330|
|Issue:||Date: Spring, 2010 Source Volume: 22 Source Issue: 1|
|Product:||Product Code: 2844515 Suntan & Sunscreen Lotions NAICS Code: 32562 Toilet Preparation Manufacturing SIC Code: 2844 Toilet preparations|
Norval M, Wulf HC. 2009. Does chronic sunscreen use reduce vitamin
D production to insufficient levels? Brit J Dermatol 161:4;732-6.
Exposure to ultraviolet B radiation in sunlight provides the mechanism for more than 90% of the vitamin D production in most individuals. Given the increasing prevalence of diseases and health problems linked with low vitamin D levels, concern has been expressed in recent years that the widespread use of sunscreens, particularly those with high sun protection factors, may be one of the causative factors in this pattern, by leading to a significant decrease in solar induced previtamin D3 in the skin.
This paper looks at the evidence for and against. Sunscreens prevent production of sufficient vitamin D
The authors found no trials showing that suncreens significantly suppress cutaneous vitamin D synthesis, but did find three papers with information that this might be the case.
* Ethanol or ethanol containing 5% para aminobenzoic acid (PABA) was applied to pieces of human skin prior to exposure to 30 mJ [cm.sup.-2] solar simulated radiation. Without the sunscreen 15% of the 7-dehydrocholesterol in the basal layer of the epidermis was converted to previtamin [D.sub.3] but this reaction was totally blocked by the sunscreen. Eight white skinned subjects were then whole body irradiated with one personal minimum erythemal dose from sun lamps. One hour prior to exposure a PABA based suncreen, SPF 8, was applied to the total body surface of four of the volunteers. Postexposure the vitamin [D.sub.3] concentration in the serum rose from 1.5 to 25.6 ng [mL.sup.-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 [D.sub.3].
* Twenty 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 (similar age and exposure but did not use sunscreens). Blood samples were collected during the summer. It was found that the mean 25(OH)D (vitamin 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 and 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.
* A sunscreen with SPF 15 was applied to different body areas of untanned white subjects (phototype III) one hour prior to whole body UVB irradiation. Vitamin D3 levels in the serum were measured before and 24 hours 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[D.sub.3], and >19% of the body needed to be free of sunscreen for a significant rise in serum vitamin [D.sub.3] to occur. Serum 25(OH)D levels were not measured.
Sunscreens do not prevent production of sufficient vitamin D
* A Melbourne trial involved 113 subjects aged 40 years and above where 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. The conclusion was that sufficient exposure to the sun is achieved during the Australian summer to allow adequate vitamin D production in subjects who regularly apply sunscreens.
* In Barcelona 24 elderly sunscreen users (mean age 71 years) and 19 controls were followed on five occasions over 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 (55% and 24% in the 2 years) in the controls than in the sunscreen users (35% and 33% in the 2 years). It was concluded that sunscreen protection did not increase the risk of osteoporosis in elderly women.
* In Boston 381 volunteers aged 65 years and over were examined 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 three month period. 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). Sunscreen use was shown to be positively correlated with serum 25(OH)D levels. One explanation for this relationship is that sunscreens are used particularly to avoid sunburn on days of sunbathing with the intention to tan.
* In Queensland a study assessed serum 25(OH)D status in 124 healthy adults aged 18-87 years 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.
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. This is mainly due to inadequacies in their application to the skin and because people using sunscreens may also expose themselves to more sun than nonsunscreen users.
Kim Hunter MNHAA
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