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Slip, slop and slap: is this still sound advice? - About Health | Blog

Slip, slop and slap: is this still sound advice?

For New Zealanders summer is synonymous with three other ‘S’ words:  slip, slop and slap.  This nationwide sun protection campaign encouraging us to wear shirts, hats, sun glasses and sunscreen has seen the nation converted to shade coveting, sunscreen junkies.

Since the launch of this campaign incidence of the two most common forms of skin cancer (basal-cell and squamous-cell carcinoma) has decreased.  However incidence of the most lethal form of skin cancer – melanoma, which accounts for 75% of all skin cancer deaths, has increased. (1-7)

Is avoiding the sun good for our health?

While New Zealanders are encouraged to cover up to avoid the ‘risks of sun exposure’ an equally serious health risk associated with lack of sun exposure goes unaddressed by health officials - that of a vitamin D deficiency. UVB light is the most abundant natural source of vitamin D for the body, triggering the synthesis of vitamin D in the skin.  By blocking UVB light sunscreens inhibit vitamin D synthesis.  An SPF factor as low as 8 can block up to 95% of vitamin D synthesis. A quarter of a century since the education around sun protection began; vitamin D deficiency is now re-emerging as a major public health issue worldwide. (8, 9) A tell-tale sign is the huge rise in the number of cases of rickets, a bone disease that occurs in children whereby the bones become soft, weak and deformed due to a vitamin D deficiency.  Rickets was thought to have been vanquished in the early 20th Century. The New Zealand Ministry of Health poses vitamin D deficiency rates in children at ‘only’ 10% and around 5% in adults, with a further 27% of adults below the recommended blood level of vitamin D. (10)  While this already accounts for a generous third of all adult New Zealander’s, if figures from other countries (Scandinavia, United States, Canada, Australia) subject to the same sun-protection campaigns are taken into consideration, these figures are likely to be conservative. A recent study published in the Medical Journal of Australia found that of all children studied 55% had a vitamin D deficiency*and 5% had rickets. (8)  At present it is estimated that approximately one billion people worldwide are vitamin D deficient/insufficient. (11) *deficiency is defined as a reading of 25-hydroxyvitamin D [25OHD] ≤ 50 nmol/L

Why should we be so concerned about Vitamin D?

Because a vitamin D deficiency may be more life threatening than sun exposure. Though classed as a vitamin, vitamin D is in fact an inactive ‘pro-hormone’.  Formed in the skin from cholesterol, vitamin D (cholecalciferol) is then modified in the liver and then kidneys to its active form – the hormone calcitriol.  Like all hormones calcitriol is a key controller in the body and multiple body systems cannot function adequately in its absence. Vitamin D’s most well-known role is that of regulating calcium and phosphate absorption and the growth and remodelling of bones and teeth. A vitamin D deficiency leads to low bone density (osteoporosis), bone thinning (osteomalacia) and bone deformities (rickets). (12) But beyond the bone, most organs in the body (including the brain, prostate, colon, heart and lungs) have been found to be able to generate vitamin D independently for their own purposes, indicating the significance of vitamin D in human health. Vitamin D is critical for healthy immune function and insufficient vitamin D leads to immune suppression.  It acts as a natural antibiotic defending against invaders, as a chemical messenger activating certain immune cells and is involved in anti-inflammatory pathways. Unsurprisingly vitamin D deficiency is implicated in many diseases: auto-immunity, cardiovascular disease, multiple sclerosis, depression, schizophrenia, Alzheimer’s disease, asthma, allergies, type 1 diabetes, Crohn’s disease and allergies and increases risk of mortality. (11, 13-17, 18) But what may be most shocking to a nation of dutiful sun-avoiders is the fact that vitamin D actually exerts protective effects against many forms of cancer, including melanoma.  You are 30% more likely to survive breast, prostate, colon and lung cancers, as well as lymphoma and melanoma if you have high vitamin D levels (19) and low vitamin D levels worsen the outcomes in all aforementioned cancers.  (20-26) Though those down under have the highest rates of melanoma (and all other types of cancer) they also have the highest survival rates. (18) Is this because of a lifetime of greater sun exposure and the protective effect of vitamin D?

So who is at greatest risk, those in the sun or the shade?

There is legitimate contention that sun exposure is even linked to melanoma.  A study published in 2009 examining the association between Vitamin D and melanoma risk in a cohort of 68,611 men and women did not demonstrate a comprehensive link between the two. (27) The correlation is weakened by three main factors: 1) melanoma is more common among those people who work indoors than among those who work outdoors; 2) in younger generations, melanoma appears more on areas that are commonly shielded from the sun (trunk and legs) than on the face and neck, and 3) melanoma sometimes arises on areas that are totally shielded from the sun (i.e. soles of the feet, palms, inside of eyeball). (18) While there is no doubt that UV light exposure is the an important risk factor for non-melanoma skin cancer, there is convincing evidence that the protective effect of less intense UV light exposure outweighs its potentially mutagenic side effects. In other words, moderate sun exposure is in fact better for you than none at all. (11, 28) In the next issue we will take a look at the recommendations made by the New Zealand Ministry of Health and whether these are adequately addressing the needs of New Zealanders; how much sun is good for your health; and what part vitamin D supplements can play in keeping you in healthy. References (1) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1694089/pdf/amjph00541-0112.pdf (2) Westerdahl, J.; Ingvar, C.; Masback, A.; Olsson, H. (2000). "Sunscreen use and malignant melanoma". International Journal of Cancer. Journal International Du Cancer 87 (1): 145–50. doi:10.1002/1097-0215(20000701)87:1<145::AID-IJC22>3.0.CO;23.PMID 10861466. (3) Lee JAH. The relationship between malignant melanoma of the skin and exposure to sunlight. Photochem PhotobioL 1989;50:493-496. (4) Jensen OM, Bolander AM. Trends in malignant melanoma of the skin. WHO Stat Q.1980;33:2-26.15. (5) Magnus K. Incidence of malignant melanoma of the skin in 5 Nordic countries:significance of solar radiation. Int J Cancer.1977;20:477.  (6) Magnus K. Malignant melanoma in Norway.Tidsskr Nor Laegeforen. 1986;106:2309-2313. (7) Gallagher RP, Elwood JM, Hill GB. Risk factors for cutaneous malignant melanoma: the Western CanadaMelanomaStudy.Rec Res Cancer Res. 1986;102:38-55. (8) Munns C. et al.,Incidence of vitamin D deficiency rickets among Australian children: an Australian Paediatric Surveillance Unit study,  Med J Aust 2012; 196 (7): 466-468.  doi: 10.5694/mja11.10662https://www.mja.com.au/journal/2012/196/7/incidence-vitamin-d-deficiency-rickets-among-australian-children-australian (9) Munns C, Zacharin MR, Rodda CP, et al. Prevention and treatment of infant and childhood vitamin D deficiency in Australia and New Zealand: a consensus statement. Med J Aust 2006; 185: 268-272 (10) http://www.health.govt.nz/yourhealth-topics/nutrition/vitamin-d (11) Mason RS, Reichrath J., Sunlight Vitamin D and Skin Cancer. 2011;16(9):1215-27. Anticancer Agents Med Chem. 2012 Oct 12. (12) UtigerR. The need for more vitamin D. N Engl J Med. 1998;338(12): 828–829. (13) Hedelin M, Dietary intake of fish, omega-3, omega-6, polyunsaturated fatty acids and vitamin D and the prevalence of psychotic-like symptoms in a cohort of 33,000 women from the general population, BMC Psychiatry. 2010; 10: 38. Published online 2010 May 26. doi:  10.1186/1471-244X-10-38 (14) Hoogendijk WJ, Depression is associated with decreased 25-hydroxyvitamin D and increased parathyroid hormone levels in older adults, Arch Gen Psychiatry. 2008 May;65(5):508-12. (15) Giovannucci E, Liu Y, Hollis BW, Rimm EB. (2004). 25-Hydroxyvitamin D and risk of myocardial infarction in men - A prospective study. Archives of Internal Medicine 168(11):1174-1180. (16) Holick MF. (2004). Vitamin D: importance in the prevention of cancers, type 1 diabetes, heart disease, and osteoporosis. American Journal of Clinical Nutrition 79(3):362-371. (17) Scragg R. (2007). Vitamin D, Sun exposure and Cancer. A review prepared for the Cancer Society of New Zealand by School of Population Health, University of Auckland, September 2007. (18) Wishart, Ian, Vitamin D – is this the miracle vitamin, 2012, Howling at the Moon Publishing Ltd, Auckland, New Zealand. (19) Moan et al, Addressing the health benefits and risks involving vitamin D or skin cancer, of increased sun exposure, Proceedings of the National Academy of Sciences, PNAS, Jan 15 2008, vol 105 no.2 668-673 (20) Garland C, Garland F. Do sunlight and vitamin D reduce the likelihood of colon cancer? Int J Epidemiol. 1980;9: 227–231 (21) Gorham E, Acid haze air pollution and breast and colon cancer in 20 Canadian cities, Can J Pub Health, 1989;80:96-100 (22) Garland CF, Geographic variation in breast cancer mortality in the United States: a hypothesis involving exposure to solar radiation, Prev Med., 1990;19:614-62 (23) Lefkowitz ES, Garland CF. Sunlight, vitamin D, and ovarian cancer mortality rates in US women. Int J Epidemiol. 1994;23(6):1133–1136 (24) SchwartzGG, Hulka BS. Is vitamin D deficiency a risk factor for prostate cancer? (Hypothesis). Anticancer Res. 1990;10(5A):1307–1311 (25) Buttigliero C et al, Prognostic role of vitamin d status and efficacy of vitamin D supplementation in cancer patients: a systematic review. Oncologist. (26) Garland CF et al, The role of vitamin D in Cancer Prevention, American Journal of Public Health: February 2006, Vol. 96, No. 2, pp. 252-261. doi: 10.2105/AJPH.2004.045260 (27) Asgari, M M, et al (2009), A Cohort Study of Vitamin D Intake and Melanoma Risk, Am J Public Health 129 (7):1675-1680, doi:10.1038/jid.2008.451. PMC 2695831. PMID 19194478. (28) Lappe et al, Vitamin D and calcium supplementation reduces cancer risk, Am J Cl Nutr, 2007, 85(6):1586-91