Vitamin D and Pain
By David Kiefer, MD
Research Fellow, Department of Family Medicine, University of Wisconsin; Clinical Assistant Professor of Medicine, Arizona Center for Integrative Medicine, University of Arizona
Dr. Kiefer reports no financial relationships relevant to this field of study. This article originally appeared in the January 2014 issue of Integrative Medicine Alert.
Source: Sanghi D, et al. Does vitamin D improve osteoarthritis of the knee: A randomized controlled pilot trial. Clin Orthop Relat Res 2013;471:3556-3562.
Vitamin d should probably be the Time Magazine nutrient of the year (decade?), given the variety of body systems with some physiological connection to the effects of vitamin D. Add to the list pain — in this case pain from osteoarthritis (OA) of the knee. In 107 people with documented knee OA and vitamin D insufficiency (serum 25-hydroxyvitamin D (25(OH)D) ≤ 50 nmol/L), the half allocated to receiving oral vitamin D3 (or cholecalciferol, dosed at 60,000 IU daily for 10 days and then 60,000 IU once monthly for the remainder of the 1-year study) had less pain as per the visual analog scale (VAS) and WOMAC scores (effect sizes 0.37 and 0.78, respectively) and improved knee function at 12 months when compared to the placebo group. There were no differences between the groups with respect to knee stiffness. The serum 25(OH)D increased in the vitamin D group by 45.7 nmol/L, whereas the placebo group only increased 2.1 nmol/L after the year. A major limiting factor of these findings was the low effect sizes, equating with only about 1 mm on the VAS score and 2 points on the WOMAC, making the authors question the clinical relevance. The authors consider these results important for the planning of future clinical trials that would have sufficient power to detect clinically significant differences.