People with low levels of vitamin D circulating in their blood stream have been shown in epidemiological studies to be more susceptible to osteoarthritis. Such observational studies have also suggested that higher levels of vitamin D might have a positive effect on the progression of arthritis.
Because of these preliminary data, scientists at Tufts Medical Center organized a two-year randomized, placebo-controlled, double-blind trial of vitamin D supplementation. The subjects were suffering from pain and stiffness due to osteoarthritis of their knees. The participants who were randomized to receive vitamin D started at 2,000 International Units a day. The dose was increased if necessary to make sure that blood levels of the active form of this nutrient reached at least 36 nanograms per milliliter. By the end of the two-year trial, nearly two-thirds of those receiving vitamin D had reached the target blood levels. Although there was a trend towards reduced knee pain among those who received vitamin D, the difference was not statistically significant.
[JAMA, Jan. 9, 2013]
We were surprised to note that not everyone managed to get their blood levels of 25-hydroxyvitamin D into the target range, even though some people got doses as high as 8,000 IU/day. To learn more about vitamin D, how it is measured in the body, and what an appropriate dose might be, we suggest our Guide to Vitamin D Deficiency.D