BACKGROUND: The effect of season on vitamin D status is often overlooked in studies of optimal vitamin D concentrations and in clinical practice. OBJECTIVES: We aimed to determine the effects of seasonal variation of 25-hydroxyvitamin D [25(OH)D] on a previously selected minimum concentration for vitamin D sufficiency (50 nmol/L) and to determine whether fat mass modifies these effects. DESIGN: A cross-sectional study evaluated 1606 healthy postmenopausal women and 378 older men from Auckland, New Zealand, who were undergoing single measurements of 25(OH)D. RESULTS: Concentrations of <50 nmol 25(OH)D/L were seen in 49% (range: 23%-74%) of women and 9% (range: 0%-26%) of men when measured, but 73% of women and 39% of men were predicted to have trough 25(OH)D concentrations < 50 nmol/L, according to the demonstrated seasonal variation. The predicted duration of 25(OH)D concentrations < 50 nmol/L was 250 d/y in women and 165 d/y in men. CONCLUSION: Seasonal variation significantly affects the diagnosis of vitamin D sufficiency, which requires seasonally adjusted thresholds individualized for different locations. Clinicians should consider the month of sampling and the amount of body fat when interpreting 25(OH)D measurements.
BACKGROUND: The effect of season on vitamin D status is often overlooked in studies of optimal vitamin D concentrations and in clinical practice. OBJECTIVES: We aimed to determine the effects of seasonal variation of 25-hydroxyvitamin D [25(OH)D] on a previously selected minimum concentration for vitamin D sufficiency (50 nmol/L) and to determine whether fat mass modifies these effects. DESIGN: A cross-sectional study evaluated 1606 healthy postmenopausal women and 378 older men from Auckland, New Zealand, who were undergoing single measurements of 25(OH)D. RESULTS: Concentrations of <50 nmol 25(OH)D/L were seen in 49% (range: 23%-74%) of women and 9% (range: 0%-26%) of men when measured, but 73% of women and 39% of men were predicted to have trough 25(OH)D concentrations < 50 nmol/L, according to the demonstrated seasonal variation. The predicted duration of 25(OH)D concentrations < 50 nmol/L was 250 d/y in women and 165 d/y in men. CONCLUSION: Seasonal variation significantly affects the diagnosis of vitamin D sufficiency, which requires seasonally adjusted thresholds individualized for different locations. Clinicians should consider the month of sampling and the amount of body fat when interpreting 25(OH)D measurements.
Authors: Abigail B Shoben; Bryan Kestenbaum; Gregory Levin; Andrew N Hoofnagle; Bruce M Psaty; David S Siscovick; Ian H de Boer Journal: Am J Epidemiol Date: 2011-11-23 Impact factor: 4.897
Authors: Michael C Sachs; Abigail Shoben; Gregory P Levin; Cassy Robinson-Cohen; Andrew N Hoofnagle; Nancy Swords-Jenny; Joachim H Ix; Matthew Budoff; Pamela L Lutsey; David S Siscovick; Bryan Kestenbaum; Ian H de Boer Journal: Am J Clin Nutr Date: 2013-04-24 Impact factor: 7.045
Authors: Marjorie L McCullough; Stephanie J Weinstein; D Michal Freedman; Kathy Helzlsouer; W Dana Flanders; Karen Koenig; Laurence Kolonel; Francine Laden; Loic Le Marchand; Mark Purdue; Kirk Snyder; Victoria L Stevens; Rachael Stolzenberg-Solomon; Jarmo Virtamo; Gong Yang; Kai Yu; Wei Zheng; Demetrius Albanes; Jason Ashby; Kimberly Bertrand; Hui Cai; Yu Chen; Lisa Gallicchio; Edward Giovannucci; Eric J Jacobs; Susan E Hankinson; Patricia Hartge; Virginia Hartmuller; Chinonye Harvey; Richard B Hayes; Ronald L Horst; Xiao-Ou Shu Journal: Am J Epidemiol Date: 2010-06-18 Impact factor: 4.897
Authors: Gregory P Levin; Cassianne Robinson-Cohen; Ian H de Boer; Denise K Houston; Kurt Lohman; Yongmei Liu; Stephen B Kritchevsky; Jane A Cauley; Toshiko Tanaka; Luigi Ferrucci; Stefania Bandinelli; Kushang V Patel; Emil Hagström; Karl Michaëlsson; Håkan Melhus; Thomas Wang; Myles Wolf; Bruce M Psaty; David Siscovick; Bryan Kestenbaum Journal: JAMA Date: 2012-11-14 Impact factor: 56.272