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Summary: Sunlight deprivation results in vitamin D deficiency but serum vitamin D levels can be maintained above 50nmol/L when supplemented with 50,000IU at least every alternate month. Introduction: Antarctic expeditioners are exposed to prolonged sunlight deprivation resulting in vitamin D deficiency. We hypothesised that monthly dosing of 50,000 IU vitamin D (~1,600 IU daily) will increase serum 25-hydroxyvitamin D (25(OH)D), suppress parathyroid hormone (PTH) and improve bone mineral density (BMD), 50,000 IU alternate months (~800 IU daily) will maintain these measures, while a single 50,000 IU dose pre-departure (~1,00 IU daily) will not be protective. Methods: This was a randomised double-blind study involving 110 healthy adults: 91 males, mean age 41 years (range 24-65 years) working in Antarctica for up to 12 months, who we administered 50,000 IU vitamin D3 monthly, alternate months or a single dose pre-departure. Serum 25(OH)D, PTH, osteocalcin, CTx and calcium were assessed at baseline, mid- and end of expedition. Proximal femur and lumbar spine BMD were assessed pre- and post-expedition. Results: Baseline 25(OH)D was 59 ± 14 nmol/L. By mid-expedition, 25(OH)D increased by 7 nmol/L in those supplemented monthly ( p < 0.05) and remained unchanged in those supplemented in alternate months. In those given a single dose pre-departure, 25(OH)D decreased by 8 nmol/L ( p < 0.05) and PTH increased by 27% ( p < 0.09). Serum osteocalcin increased by ~22% in all groups but BMD remained unchanged. If serum 25(OH)D was >50 nmol/L at baseline, 25(OH)D was maintained above this level with all regimens. If 25(OH)D was <50 nmol/L at baseline, monthly or alternate month regimens were needed to achieve levels >50 nmol/L, the single pre-departure dose was ineffective. Conclusion: During sunlight deprivation of up to 12 months, serum 25(OH)D levels can be maintained above 50 nmol/L when expeditioners are provided with 50,000 I U at least every alternate month. [ABSTRACT FROM AUTHOR]

Summary: In this large population-based study, walking was assessed twice yearly for a week, each time by pedometer, had consistent clinically important associations with hip areal bone mineral density (aBMD) in both sexes which appears most important in those over 65 years of age suggesting that walking becomes more important with increasing age. Introduction: Walking is advocated as a preventative strategy for osteoporosis but the evidence is conflicting in females and lacking in males. The aim of this population-based longitudinal study in community dwelling older people ( n = 875) was to determine the association between pedometer determined ambulatory activity (PAA) and bone mass. Methods: Bone mass was assessed as aBMD at the hip and spine using dual X-ray absorptiometry. Steps per day were measured using pedometers for 1 week on four occasions at least 6 months apart. Data were analysed using linear mixed models. Results: At baseline, PAA was positively associated with hip aBMD. An age interaction was present with steps having a stronger association for those aged over 65 years. Longitudinally, the effect of steps on hip aBMD was constant, but not additive over time. For those over 65 years, the difference in hip aBMD between the lowest and highest steps quartiles ranged from 3.1% to 9.4%. With regard to the spine, the relationship between daily steps and spine aBMD was modified by sex. For males; there was no significant relationship between steps and spine aBMD. However, for females, higher steps were associated with higher spine aBMD with the effect being constant over time but not additive. There was no evidence of a threshold effect. Conclusion: In conclusion, pedometer-determined ambulatory activity has consistent clinically important associations with hip aBMD in both sexes which appears most important in those over 65 years of age. The associations for spine aBMD were both weaker and inconsistent suggesting site specificity. [ABSTRACT FROM AUTHOR]