25-hydroxyvitamin D concentration, vitamin D intake and joint symptoms in postmenopausal women

Abstract

Introduction: Low 25-hydroxyvitamin D (25(OH) D) concentrations have been associated with radiologic worsening of osteoarthritis in some reports. However, the results are mixed and few studies have evaluated associations between 25(OH) D concentrations and both total vitamin D intake and clinical joint symptoms.

Study design: Cross-sectional analyses of information from a subset of 1993 postmenopausal women obtained at baseline entry in the Women's Health Initiative Calcium plus Vitamin D clinical trial.

Main outcome measures: 25(OH) D concentration, total vitamin D intake (diet plus supplements), presence and severity of joint pain and joint swelling.

Results: The 25(OH) D levels were commonly low with 53% having deficient (<50 nmol/L) and only 17% having sufficient (>72 nmol/L) levels. Joint pain (reported by 74%) and joint swelling (reported by 34%) were also commonly reported. 25(OH) D concentrations were modestly correlated with total vitamin D intake (R=0.29, p<0.0001); however, considerable variability in 25(OH) D concentrations for a given vitamin D intake was seen. In adjusted linear regression models, lower serum 25(OH) D concentrations were associated with higher average joint pain score (P=0.01 for trend) with differences most apparent in the lowest 25(OH) D levels sextile.

Conclusions: Relatively low 25(OH) D levels and a high frequency of joint symptoms were common in this population of postmenopausal women. Total vitamin D intake was only modestly associated with 25(OH) D. Low serum 25(OH) D concentrations were associated with higher joint pain scores. These findings can inform the design of future intervention trials.

Figure 1. Vitamin D intake (diet plus supplements) and serum 25-hydroxyvitamin D levels at baseline (n=1957)

Individual vitamin D intake (diet plus supplementation) and serum 25-hydroxyvitamin D concentration at baseline. Serum 25-hydroxyvitamin D levels were obtained at baseline entry into the calcium plus vitamin D clinical trial. Results from the 1993 women identified as control subjects from the nested case control study are shown. Daily intakes of dietary and supplemental vitamin D were determined from a food frequency questionnaire (for diet) and a total vitamin D intake was associated with 25-hydroxyvitamin D levels (n=0.29, p<0.001); however, considerable variability in 25-hydroxyvitamin D levels for a given vitamin D intake is seen.