Osteoarthritis (OA), also known as degenerative joint disease, is a mechanical abnormality involving degradation of joints, including cartilage and bone. The joints just wear out from a lifetime of use. Common symptoms include joint pain, tenderness and stiffness.
Osteoarthritis affects nearly 27 million people in the United States, accounting for 25% of visits to primary care physicians. It is estimated that 80% of the population have radiographic evidence of OA by age 65.
Does vitamin D help OA? Dr. Timothy McAlindon and colleagues at Tufts Medical Center wanted to know, and recently conducted a study to find out. They found that vitamin D does not help.
McAlindon T, LaValley M, Schneider E, Nuite M, Lee JY, Price LL, Lo G, Dawson-Hughes B. Effect of vitamin D supplementation on progression of knee pain and cartilage volume loss in patients with symptomatic osteoarthritis: a randomized controlled trial. JAMA. 2013 Jan 9;309(2):155-62.
They randomized 146 participants to a vitamin D group or a placebo group. Sixty-four patients finished the study taking vitamin D and 60 finished it on placebo. For the vitamin D arm, participants took at least 2000 IU/day, and researchers increased the dose to ensure that levels were at least 36 ng/mL. Twenty-three participants received vitamin D dose escalations as follows:
- 18 patients had their dose increased to 4000 IU/day
- 4 to 6000 IU/day
- 1 to 8000 IU/day
Knee pain decreased in both groups with no significant differences between groups at any time. Cartilage volume decreased equally in both groups by about 4% during the two years of the study. There were no significant differences in pain relief or functional assessments between groups, although trends in pain (p=.17) and functionality (P=.07) favored the treatment group.
However, the mean plasma 25-hydroxyvitamin D level rose in the treatment group only rose from 22.7 to 38.5ng/mL after 24 months of treatment. Despite the goal of getting the entire treatment arm above 36 ng/ml with dose escalation, only 61% of the vitamin D group reached the target level of 36 ng/mL by the 24th month. The authors did not explain why their dose escalation regimen did not get all participants above their stated goal of 36 ng/ml.
It is unlikely that vitamin D can repair worn out joints, although I do find it likely that higher vitamin D doses can help the pain of OA. In fact, their own study showed that trends favored the treatment group in both pain and functionality.