Seasonal changes in vitamin D status and bone turnover in healthy Irish postmenopausal women

Int J Vitam Nutr Res. 2007 Sep;77(5):320-5. doi: 10.1024/0300-9831.77.5.320.

Abstract

Objectives: To examine the effect of season on biochemical markers of bone turnover in 51-to 75-year-old Irish women and to investigate whether such changes are related to vitamin D status.

Design: Longitudinal observational study.

Setting: Cork, Ireland (52 degrees N).

Subjects: 76 apparently healthy, free-living postmenopausal women (aged 51-75 years), not taking any medication and free from any condition likely to affect vitamin D status or calcium/bone metabolism.

Results: Serum 25-hydroxyvitamin D [S-25(OH)D] showed a clear seasonal variation with significantly higher (p < 0.001) values during late summer than late winter. Both urinary pyridinoline (Ur-Pyr) (p < 0.01) and deoxypyridinoline (Ur-Dpyr) (p < 0.001), but not serum parathyroid hormone or osteocalcin, showed a marked seasonal variation with lowest values during late-summer. Stratifying women into those with S-25(OH)D levels > or = or <50 nmol/L (vitamin D adequate and inadequate, respectively) during late-winter, showed that Ur-Pyr and Ur-Dpyr in both groups were significantly (p < 0.05) lower during late summer, and the magnitude of the reduction from winter to summer was similar in both groups.

Conclusion: Seasonal changes in bone resorption markers appeared to be linked to seasonal changes in vitamin D status. Further research is needed to investigate the impact of these changes on risk of bone loss and fracture.

MeSH terms

  • Aged
  • Amino Acids / urine
  • Biomarkers / blood
  • Biomarkers / urine
  • Bone Resorption / epidemiology
  • Bone Resorption / urine
  • Female
  • Follow-Up Studies
  • Humans
  • Ireland / epidemiology
  • Longitudinal Studies
  • Middle Aged
  • Nutritional Status
  • Osteocalcin / blood
  • Osteoporosis, Postmenopausal / blood
  • Osteoporosis, Postmenopausal / epidemiology*
  • Osteoporosis, Postmenopausal / urine
  • Postmenopause
  • Reference Values
  • Seasons*
  • Vitamin D / blood*
  • Vitamin D Deficiency / blood
  • Vitamin D Deficiency / epidemiology*

Substances

  • Amino Acids
  • Biomarkers
  • Osteocalcin
  • Vitamin D
  • pyridinoline
  • deoxypyridinoline