Make vitamin D while the sun shines, take supplements when it doesn't: a longitudinal, observational study of older adults in Tasmania, Australia

• Published in: PloS one 2013-03, Vol.8 (3), p.e59063-e59063
• Main Authors: Pittaway, Jane K, Ahuja, Kiran D K, Beckett, Jeffrey M, Bird, Marie-Louise, Robertson, Iain K, Ball, Madeleine J
• Format: Article
• Language: English
• Subjects: Aged; Aged, 80 and over; Calcifediol - blood; Dietary Supplements; Female; Humans; Longitudinal Studies; Male; Middle Aged; Seasons; Sunlight; Tasmania; Vitamin D; Vitamin D - blood
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0059063

Low vitamin D status has been associated with a number of chronic conditions, particularly in older adults. The aim of this study was to identify how best to maintain optimum vitamin D status throughout the year in this high-risk population. The main objectives of the study were to assess seasonal vitamin D status; identify the main determinants of vitamin D status; determine if taking part in the study led to alterations in participant behaviour and vitamin D status. A longitudinal design across four consecutive seasons observed ninety-one 60-85 year old community-dwelling adults in Tasmania (41π S) over 13 consecutive months, with a follow-up assessment at next winter's end. Associations between solar UVB exposure, sun protection behaviours, dietary and supplemental vitamin D with serum 25(OH)D concentrations were assessed. Variation in serum 25(OH)D demonstrated an identical pattern to solar UVB, lagging 8-10 weeks. Serum 25(OH)D was positively associated with summer UVB (mean 15.9 nmol/L; 95%CI 11.8-19.9 nmol/L, p