There have been many studies this past few years on knee arthritis and vitamin D. Regrettably, the conclusions have been all over the map. Now a new study with a better design says that low Vitamin D is associated with knee arthritis progression.
Vitamin D is a fat soluble hormone that’s made by your skin as it’s exposed to sun or that you can get in various foods like fish, milk, cheese, and eggs. It’s involved in maintaining healthy bones, so it’s not surprising that people have thought it could be involved in arthritis, as the bones often change shape due to collapse in the severest forms of the disease.
To date, the medical research on arthritis and vitamin D has been all over the place. Some studies have shown that low vitamin D is associated with more knee arthritis. Other studies have gone the other way, finding no link between vitamin D levels and knee arthritis. The biggest problem with this body of research to date has been that they’re “snapshot studies” where the fact that some people have low vitamin D levels is used to see if these patients also happen to have arthritis. The next best kind of study would look at whether patients with low vitamin D are more likely to go on to develop arthritis. This is the kind of study a group of researchers just published.
The new study looked at more than 400 patients in a larger study called the “Osteoarthritis Initiative” who had painful arthritis for more than a year. It then tracked vitamin D levels over approximately 3 years while the larger study was measuring the degree of arthritis on x-rays. This study did show a three times greater risk of arthritis progression with vitamin low D levels (<15 micrograms/L) and high parathyroid hormone (PTH) levels. PTH is a hormone that kicks into high gear when vitamin D is low which causes he body to take calcium from the bones (making the bones weaker).
The upshot? While I’m sure this isn’t the final word on knee arthritis and Vitamin D, this study is a better one to “hand your hat on” than some of the prior installments in this debate. My recommendation for now would be to have your vitamin D levels checked and if they’re low and you have arthritis, supplement accordingly! If your PTH is also high, then this means that you’re literally dissolving your own bones to make calcium…ouch!!