Skeletal and hormonal responses to sunlight deprivation in Antarctic expeditioners
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Serum 25(OH)D levels decline without sunlight exposure. We studied 120 expeditioners to Antarctica to determine the skeletal and hormonal responses to sunlight deprivation. With emerging vitamin D insufficiency, serum calcium decreased, PTH increased, and bone loss at the proximal femur was observed. Baseline serum 25(OH)D levels >100 nmol/L prevented vitamin D insufficiency.
Vitamin D stores deplete without adequate sunlight exposure unless supplementation is provided. We studied 120 healthy adults who spent a year in Antarctica as a model for sunlight deprivation to define the timing and magnitude of the skeletal and hormonal responses to emerging vitamin D insufficiency.
Fasting blood samples were assessed at baseline, 6 and 12 months for serum 25-hydroxyvitamin D (25(OH)D), osteocalcin (OC), bone formation (P1NP) and resorption (CTx), PTH and calcium. Lumbar spine and proximal femur BMD was measured using DXA. Differences over time were determined using repeated measures ANOVA. Percent changes were expressed as (Δ value/(value A + value B)/2) × 100. Relationships between outcome measures were determined using Spearman’s correlations.
Vitamin D insufficiency (<50 nmol/L) was observed in 85% of expeditioners by 6 months when serum calcium decreased and PTH increased (p < 0.01). By 12 months, OC increased by 7.4 ± 3.0% (p < 0.05), and BMD decreased by 1.0 ± 2.0% at the total proximal femur (p < 0.05). For those with vitamin D sufficiency at baseline (>50 nmol/L), sunlight deprivation produced vitamin D insufficiency within 4 months unless baseline values were >100 nmol/L.
Supplementation may be necessary for expeditioners with limited access to UV light.
KeywordsBone loss Sunlight Vitamin D
The authors thank Robin Taylor, Dr. Roland Watzl and Melissa Kingston (AAD), research nurses Kylie King and Judy Tan (Austin Health), Antarctic medical practitioners Drs. Tanya Kelly, Andy Williams, Malcolm Arnold, John Birss, Graham Denyer, James Double, Jim Bumak, and Lloyd Fletcher, Drs. Colin Roy, Stuart Henderson, and Peter Gies (ARPANSA) for use of UV data, Suzanne Sparshott, Rose Ford, and Furley Johston (Menzies) and Jane Karpavicius, Tanya Mewbury, and Mary-Kate Inkster (Monash University).
This project was support by Australian Antarctic Science grants.
Conflicts of interest
- 1.Lips P, Duong T, Oleksik A, Black D, Cummings S, Cox D, Nickelsen T (2001) A global study of vitamin D status and parathyroid function in postmenopausal women with osteoporosis: baseline data from the multiple outcomes of raloxifene evaluation clinical trial. J Clin Endocrinol Metab 86(3):1212–1221PubMedCrossRefGoogle Scholar
- 13.Working group of the Australian and New Zealand Bone and Mineral Society, Endocrine Society of Australia and Osteoporosis Australia (2005) Vitamin D and adult bone health in Australia and New Zealand: a position statement. Med J Aust 182(6):281–285Google Scholar
- 17.Storm D, Eslin R, Porter ES, Musgrave K, Vereault D, Patton C, Kessenich C, Mohan S, Chen T, Holick MF, Rosen CJ (1998) Calcium supplementation prevents seasonal bone loss and changes in biochemical markers of bone turnover in elderly New England women: a randomized placebo-controlled trial. J Clin Endocrinol Metab 83(11):3817–3825PubMedCrossRefGoogle Scholar
- 22.Gies P, Javorniczky J, Roy C, Ayton J, Watzl R, Cooley H, Kingston M (2006) Measurement of the UVR Exposures of Expeditioners on Antarctic Resupply Voyages National Institute of Water and Atmospheric Research UV Workshop-UV Radiation and its Effects:an Update, Dunedin, New ZealandGoogle Scholar