2.3 Vitamin D
Background
Cancer Council Australia’s position statement on the risks and benefits of sun exposure was developed to balance the risks of keratinocyte cancer (KC) and melanoma with vitamin D requirements.
This position statement is approved by the Australian and New Zealand Bone and Mineral Society, the Australasian College of Dermatologists, Cancer Council Australia, Endocrine Society of Australia and Osteoporosis Australia (see: Cancer Council Australia Position statement Sun exposure and vitamin D - risks and benefits).
Summary of Cancer Council Australia’s position statement
Cancer Council Australia's position statement on the risks and benefits of sun exposure includes the following key messages for health professionals and the general public.
A balance is required between avoiding an increase in the risk of skin cancer by excessive sun exposure and achieving enough sun exposure to maintain adequate vitamin D levels.
There is strong evidence that vitamin D is beneficial for bone development and maintaining musculoskeletal health. Severe vitamin D deficiency leads to osteomalacia (softening of bones) in adults,[1] and rickets in children,[2] along with muscle weakness. Children and adults with low 25-hydroxyvitamin D in children and adults may have no obvious symptoms.
Vitamin D forms in the skin as a result of exposure to the ultraviolet (UV) B wavelengths in sunlight. Current evidence shows that sun exposure for short periods of most days of the week (well below a sunburning dose) is sufficient to maintain adequate vitamin D levels. On the other hand, there is considerable evidence showing that excessive sun exposure causes skin cancer. Research suggests that prolonged sun exposure does not cause vitamin D levels to continue to increase further[3] but does increase the risk of skin cancer.[4] Short periods (a few minutes) of sun exposure to a larger skin surface may be more efficient at producing vitamin D than long periods to a small skin surface[5] and daily exercise also assists the body to produce vitamin D.[6]
People who wear concealing clothing for religious or cultural reasons are at increased risk of vitamin D deficiency because they have very small areas of skin exposed to sunlight, and therefore may require vitamin D supplementation.[7] Women (especially those with naturally very dark skin, who are pregnant or planning pregnancy), people in institutional care, the elderly and those who are housebound should ask their medical practitioner for advice about their vitamin D requirements.
Extended sun exposure without any form of sun protection is not recommended, even for those diagnosed with vitamin D deficiency.
Production of vitamin D from exposure of the skin to sunlight is influenced by a number of factors including age, skin colour, latitude, season and time of day, making it difficult to provide advice to the population as a whole. Therefore, the recommendation for the general adult population is as follows:
When the UV index is 3 or above, a combination of sun protection measures (broad-brimmed hat, covering clothing, sunscreen, sunglasses and shade) is recommended when outdoors for more than a few minutes. Most Australian adults will maintain adequate vitamin D levels from sun exposure during typical day-to-day outdoor activities.
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References
- ↑ Bhan A, Rao AD, Rao DS. Osteomalacia as a result of vitamin D deficiency. Endocrinol Metab Clin North Am 2010 Jun;39(2):321-31, table of contents Available from: http://www.ncbi.nlm.nih.gov/pubmed/20511054.
- ↑ Paxton GA, Teale GR, Nowson CA, Mason RS, McGrath JJ, Thompson MJ, et al. Vitamin D and health in pregnancy, infants, children and adolescents in Australia and New Zealand: a position statement. Med J Aust 2013 Feb 18;198(3):142-3 Available from: http://www.ncbi.nlm.nih.gov/pubmed/23418693.
- ↑ Gilchrest BA. Sun exposure and vitamin D sufficiency. Am J Clin Nutr 2008 Aug;88(2):570S-577S Available from: http://www.ncbi.nlm.nih.gov/pubmed/18689404.
- ↑ van der Pols JC, Russell A, Bauer U, Neale RE, Kimlin MG, Green AC. Vitamin D status and skin cancer risk independent of time outdoors: 11-year prospective study in an Australian community. J Invest Dermatol 2013 Mar;133(3):637-641 Available from: http://www.ncbi.nlm.nih.gov/pubmed/23076499.
- ↑ Bogh MK, Schmedes AV, Philipsen PA, Thieden E, Wulf HC. Vitamin D production depends on ultraviolet-B dose but not on dose rate: a randomized controlled trial. Exp Dermatol 2011 Jan;20(1):14-8 Available from: http://www.ncbi.nlm.nih.gov/pubmed/21158934.
- ↑ Scragg R, Holdaway I, Jackson R, Lim T. Plasma 25-hydroxyvitamin D3 and its relation to physical activity and other heart disease risk factors in the general population. Ann Epidemiol 1992 Sep;2(5):697-703 Available from: http://www.ncbi.nlm.nih.gov/pubmed/1342321.
- ↑ Thomson K, Morley R, Grover SR, Zacharin MR. Postnatal evaluation of vitamin D and bone health in women who were vitamin D-deficient in pregnancy, and in their infants. Med J Aust 2004 Nov 1;181(9):486-8 Available from: http://www.ncbi.nlm.nih.gov/pubmed/15516192.