Low Vitamin D May Hurt Arthritic Knees

Osteoarthritis knee pain may be higher among blacks with low vitamin D

(RxWiki News) Vitamin D has been shown to play a crucial role in many functions throughout the body. Now, researchers have found Vitamin D levels could explain why black Americans may feel more pain from osteoarthritis.

In a recent study, black Americans with knee osteoarthritis had lower levels of vitamin D and more sensitivity to pain than their white counterparts.

"Get some sun to boost your bone and joint health."

Research over the past decade has revealed vitamin D is important to more than bone health. Studies have shown low levels of vitamin D may contribute to the development of cancer and diabetes.

Toni Glover, MSN, ARNP, a research nurse practitioner and doctoral candidate at the University of Florida, and colleagues set out to see if differences in vitamin D levels played a role in racial differences in patients with knee pain caused by osteoarthritis.

According to clinical practice guidelines, people with vitamin D levels between 21 and 29 ng/mL have vitamin D insufficiency. People with levels below 20 ng/mL have vitamin D deficiency. Both vitamin D insufficiency and deficiency are defined as levels of vitamin D that are lower than normal.

From their study, Glover and colleagues found 84 percent of black patients had vitamin D levels lower than 30 ng/mL. In comparison, 51 percent of white patients had levels lower than 30 ng/mL.

On average, black patients were more likely to have vitamin D deficiency, while white patients usually dealt with vitamin D insufficiency. The average vitamin D level among black patients was 19.9 ng/mL while the average level among white patients was 28.2 ng/mL.

Black patients reported feeling more pain from knee osteoarthritis than whites.

Patients with lower levels of vitamin D were more sensitive to heat and mechanical pain (pressure on the knee and forearm).

According to Glover, these findings suggest that vitamin D plays a part in the differences in sensitivity to pain between blacks and whites.

"However, further studies are needed to fully understand the link between low vitamin D levels and racial disparities in pain," she said.

Glover continued that although vitamin D toxicity (high levels of vitamin D) is rare, it is still possible and older adults should talk to their doctor about the safety of taking vitamin D supplements.

"It may be warranted that older black Americans with chronic widespread pain be screened for vitamin D deficiency to reduce disparities in pain," she concluded.

The study included 94 participants with knee osteoarthritis. Of these 45 were black and 49 were white.

Participants were asked to complete questionnaires about their symptoms. In addition, participants went through testing that included sensitivity to heat and pressure on the affected knee and forearm.

The research was funded by the National Institute on Aging, the John A. Hartford Foundation and the Mayday Fund.

The study was published in Arthritis & Rheumatism, a journal of the American College of Rheumatology. 

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Review Date: 
November 6, 2012