Mar 30, 2015 09:23 PM EDT By Staff Reporter, UniversityHerald Reporter

Higher levels of vitamin D may decrease pain and improve function in obese individuals with osteoarthritis, according to a recent study.

Osteoarthritis is the most common form of arthritis affecting millions of people worldwide. It occurs when the protective cartilage on the ends of bones wears down over time, causing pain, stiffness and loss of joint movement.

Researchers at the University of Florida found that obese individuals who suffer from osteoarthritis and have adequate vitamin D levels could walk, balance and rise from sitting to standing better than obese participants with insufficient vitamin D levels. The findings suggest an association between obesity and vitamin D status for tasks such as standing from a seated position.

"Adequate vitamin D may be significant to improving osteoarthritis pain because it affects bone quality and protects cell function to help reduce inflammation. Vitamin D maintains calcium and phosphate concentration levels to keep bones strong," Toni L. Glover, lead author of the study and an assistant professor in the UF College of Nursing, said in a statement. "Increased pain due to osteoarthritis could limit physical activity, including outdoor activity, which would lead to both decreased vitamin D levels and increased obesity."

For the study, researchers analyzed blood samples for vitamin D levels from a racially diverse group of 256 middle-aged and older adults. Participants also provided a self-report of knee osteoarthritis pain and completed functional performance tasks such as balance, walking and rising from sitting to standing. Among the 126 obese participants, 68 were vitamin D-deficient while only 29 of the 130 non-obese participants were deficient, suggesting obesity is significantly associated with clinically relevant vitamin D deficiency.

Obesity is associated with vitamin D deficiency, knee osteoarthritis pain and poor functional performance. Vitamin D is stored in the liver and human fat cells, and previous research has shown that the larger fat amount in obese people can cause vitamin D to be stored instead of circulated in the body.

The Institute of Medicine recommends that adults between the ages 18 and 70 years get 600 international units of vitamin D per day and adults older than 71 years old get at least 800 international units of vitamin D per day

"Vitamin D is inexpensive, available over-the-counter and toxicity is fairly rare," Glover added.

The findings are detailed in The Clinical Journal of Pain.

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