Consuming adequate amounts of vitamin D is certainly important for preventing and treating osteoporosis. But what about osteoarthritis?
In 1996, McAllindon et al. published a study in Annals of Internal Medicine in which they looked at this question. The authors screened 556 people who were part of the Framingham Heart Study and who also had knee radiography performed. The knee radiographs were taken once between 1983 and 1985 and again between 1992 and 1993. Vitamin D levels were assessed from self-reported dietary habits and supplementation as well as blood levels of vitamin D. The authors found that those people with pre-existing knee osteoarthritis who consumed less vitamin D and had low blood levels of vitamin D were three times more likely to develop worsening osteoarthritis.
However, in those people who did not already have pre-existing osteoarthritis, low vitamin D intake and low blood levels of vitamin D did not predict development of knee osteoarthritis over the time period studied.
In 2007, Felson et al. published a study in Arthritis and Rheumatism in which they also evaluated whether vitamin D levels may impact osteoarthritis. The authors evaluated 772 people who were part of the Framingham Osteoarthritis Study. They obtained baseline x-rays of the participants' knees in 1993-1994 and again in 2002-2005. Vitamin D levels in these participants were measured between 1996 and 2000. It was found in this subset of the study that Vitamin D levels did not correlate with radiographic worsening of the knees over the 9-year interval. As part of the same study, the authors also evaluated 277 subjects who were part of the Boston Osteoarthritis of the Knee Study. In this subset, all patients had symptomatic knee osteoarthritis. These participants had knee x-rays taken as well as MRI of the symptomatic knee at baseline, 15, and 30 months. At all visits, blood samples were obtained. Vitamin D levels were analyzed. As with the Framingham Osteoarthritis Study, vitamin D levels did not correlate with risk of worsening knee osteoarthritis.
From the available data, it appears that vitamin D levels may not correlate with development of knee osteoarthritis, but once osteoarthritis is present, consuming enough vitamin D may help prevent it from worsening. The bottom line, though, is that more research on this subject is needed.
Tips For Getting Vitamin D in the Diet
Everyone should consume ample amounts of vitamin D from their diet for overall bone health. Milk is typically fortified with vitamin D but cheese, ice cream and other dairy products are usually not. Tuna, salmon, eggs, and fortified cereals are also good sources of vitamin D. About 15 minutes per day of sunshine is also a good source of vitamin D as it stimulates the body to produce its own! This limited amount of sunshine exposure should not produce damage to the skin, but be sure to protect your skin with sunscreen or the appropriate clothing for regular sun exposure and exposure for longer periods.