Catherine A. Peterson, Mary E. Heffernan, Kay A. Sisk and Susan M. Ring

Department of Nutritional Sciences, University of Missouri-Columbia, Columbia Missouri 65211 U.S.A.

Abstract

Background:  Vitamin D is a key nutrient in bone health and the vitamin D status of individuals with regular exposure to solar or artificial ultraviolet B (UVB) radiation is generally superior to those with limited exposure.

Objective: By means of a cross-sectional, observational design, explore the association of serum 25-hydroxy vitamin D (25(OH)D) concentrations and biochemical markers of bone turnover across a spectrum of vitamin D status by comparing women who regularly use tanning beds with women of minimal UVB exposure.

Methods:  A total of 69 healthy women, ages 25–82y, were recruited. Serum concentrations of 25(OH)D, intact parathyroid hormone (iPTH), leptin, bone-specific alkaline phosphatase (BAP), osteocalcin (OC), and C-terminal telopeptides of Type I collagen (CTx) were measured.

Results:  There were no significant differences in age, height, weight, BMI and dietary intakes between groups. Serum 25(OH)D concentrations were significantly higher in tanners (n = 20) compared with non-tanners (n = 49) (p < 0.0001). Serum iPTH concentrations were lower in tanners than in non-tanners (p < 0.0001) and were negatively correlated with serum 25(OH)D concentrations (r = ^–4571, p < 0.0001). Of the bone turnover markers, only serum OC concentrations were lower in tanners compared with non-tanners (p = 0.0002). After adjusting for age and menopausal status, osteocalcin was negatively correlated (r = ^–0.0178; p = 0.04) with 25(OH)D and positively correlated with iPTH (r = 0.035; p = 0.05).

Conclusions:  Our results show healthy women with regular UVB exposure via tanning beds have significantly greater vitamin D status and lower serum osteocalcin concentrations than those without and that there is a significant inverse relationship between serum serum 25(OH)D and osteocalcin concentrations which appears to be PTH-dependent.