Vitamin D Status of Adults from Tropical Australia Determined Using Two Different Laboratory Assays: Implications for Public Health Messages Madeleine Nowak* 1 , Simone L. Harrison 1 , Petra G. Buettner 1 , Michael Kimlin 1,2 , David Porter 1,3 , Lee Kennedy 4 and Rick Speare 1 1 Skin Cancer Research Group, North Queensland Centre for Cancer Research and Anton Breinl Centre for Public Health, School of Public Health, Tropical Medicine & Rehabilitation Sciences, James Cook University, Townsville, Queensland, Australia 2 Australian Sun and Health Research Laboratory, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia 3 Pathology Queensland, Queensland Health, The Townsville Hospital, Townsville, Queensland, Australia 4 School of Medicine and Dentistry, James Cook University, Townsville, Queensland, Australia Received 2 November 2010, accepted 28 April 2011, DOI: 10.1111/j.1751-1097.2011.00941.x ABSTRACT We measured serum 25 hydroxyvitamin D [25(OH)D] levels of ambulatory adults in tropical Australia to determine whether it is appropriate to continue promoting sun-safety in this population. In August 2006 (winter), self-administered questionnaires were completed by 145 Meals-on-Wheels volunteers (49.3% male; mean age 57.8 ± 14.7 years; 76.6% response) from Townsville, Queensland (Latitude 19 o S). Serum 25(OH)D was analyzed using two common assays. Mean levels were 68.3 (SD ± 18.7; range 26–142) by DiaSorin Radioimmunoassay and 83.0 (SD ± 30.8; range 30–184) by DiaSorin Liaison Ò one. No participants were 25(OH)D deficient (<25 nmol L )1 ). Nine participants (6.2%) had 25(OH)D levels between 25 and 50 nmol L )1 (insufficient), by both methods (seven with a BMI ‡ 25). Twenty-eight participants (19.3%) had one result in the insufficient range and the other in the adequate range. Thus, almost all of these free-living adults in tropical Australia had adequate vitamin D levels at the end of winter. There was poor agreement between the two 25(OH)D assays. These results suggest it is appropriate to continue promoting sun-safe mes- sages to the ambulatory Caucasian adult population of North Queensland, which has an extremely high incidence of skin cancer. The lack of agreement between the two assays is a concern. Few doctors are aware of this measurement issue. INTRODUCTION Queensland, Australia has the highest incidence of melanoma and epithelial skin cancers in the world due to the extreme levels of solar UV radiation (1,2). Since 1980, Australians have been exposed to widespread primary prevention programs resulting in improved sun protective behavior (3,4). Research from more temperate climates suggests markedly reducing sun exposure to prevent skin cancer, may lead to low vitamin D levels undermining bone health. Insufficient levels of vitamin D also appear to be associated with some autoimmune diseases, cardiovascular disease and cancers (other than skin cancer) (5–8). Recent research suggests some free-living Caucasian Australians, not just the infirmed elderly, those with dark skin, or those covered for religious or cultural reasons, have insufficient vitamin D levels (9–11), and should spend more time in the sun and ⁄ or take supplements (12,13). Humans rely on sunlight as well as diet and fortified foods to meet their biological requirements of vitamin D, with ca 90–95% of requirements being obtained from sunlight (14). Until recently it was assumed that incidental sun exposure was sufficient to ensure adequate vitamin D levels for Australians (13); it now seems this may not be the case in some regions and some population subgroups. General recommendations encouraging intentional sun exposure without specifically tailoring messages to different latitudes, seasons, skin types, and age groups can negate the achievements of the three decade long multimillion dollar Australian investment in skin cancer prevention (3). There has been much publicity about the level of sun exposure required by Australians, since the first account of the vitamin D status of Australians in 2002 (12). Since then, there has been extensive media coverage resulting in public and professional confusion (15). The effect of this confusion is likely to be greatest in sunny climates and skin-cancer prone populations such as Queensland (2,16) where Caucasian children have a higher lifetime risk of melanoma (17,18), and 20–22% of postpartum women already believed they needed to intention- ally expose their infants to sunlight to prevent vitamin D deficiency before the controversy began (19,20). This media attention has resulted in Caucasians living in a high UVR environment reducing their sun protective practices (21). It has long been assumed that free-living adults in this sunny climate have adequate vitamin D levels, and that the major concern locally is overexposure to sunlight rather than underexposure. However, the levels in tropical Australia are *Corresponding author email: madeleine.nowak@jcu.edu.au (Dr Madeleine Nowak) Ó 2011 The Authors Photochemistry and Photobiology Ó 2011 The American Society of Photobiology 0031-8655/11 Photochemistry and Photobiology, 2011, 87: 935–943 935