Improved Vitamin D Levels May Decrease Knee Disability in Osteoarthritis Patients

Newswise — Increased vitamin D levels appear to improve muscle strength and physical function for vitamin D-deficient patients with knee osteoarthritis, according to research presented this week at the American College of Rheumatology Annual Scientific Meeting in San Antonio, Texas.

While previous studies have associated vitamin D deficiencies with an increased risk for severity of knee osteoarthritis, this is the first look at vitamin levels in relation to pain and disability. The 221 patients, average age 67 years, participating in this study were measured for changes in pain, physical function, muscle strength and serum levels of vitamin D (measurable amounts of vitamin D in the blood) two or more times across a 15- and 30-month period. At the outset, the 48 percent of patients with low levels of vitamin D (at or below the minimal 20 ng/ml needed to satisfy the body's requirements) experienced more pain and disability than those with levels above 20 ng/ml. Those with deficient serum vitamin D were also weaker, but this was not significant.

The study also found that changes in vitamin D status over time predicted changes in disability. Those with sufficient serum vitamin D that became deficient over time experienced worsening disability scores, while those with deficient serum vitamin D that became sufficient over time improved their disability scores. Change in serum vitamin D levels also showed a similar pattern in changes in pain but this was not significant.

Vitamin D, which comes primarily from exposure to sunlight, promotes the absorption of calcium and phosphorus in bone mineralization, growth and repair. Sources of vitamin D are available to a lesser extent from dietary sources typically found in fortified margarine, oily fish, liver, fortified breakfast cereals and dairy products. However, the elderly are less efficient at producing vitamin D from sunlight and absorbing it from food. To address their higher risk for D deficiency, the elderly population is often directed to take a vitamin D supplement of 400-600 IU per day. (Exposure to sun should be limited to five to 15 minutes on the face, hands or arms, or arms and legs.)

"Data suggests that many people may be vitamin D deficient, especially those living in the northern hemisphere and darker skinned individuals," said Kristin Baker, PhD, Clinical Epidemiology and Research Training Unit, Boston University Boston, Massachusetts, and an investigator in the study. "The good news is vitamin D levels are easily modifiable through safe, short-term exposure to sun and/or dietary intake, and may lessen the disability and pain of osteoarthritis."

The American College of Rheumatology is the professional organization for rheumatologists and health professionals who share a dedication to healing, preventing disability and curing arthritis and related rheumatic and musculoskeletal diseases. For more information on the ACR's annual meeting, see http://www.rheumatology.org/annual.