Osteoarthritis and obesity can be a double-whammy, when it comes to pain and mobility. But new research suggests vitamin D can ease discomfort and improve physical activity in obese individuals with arthritis by lowering inflammation and strengthening bones.

The study, by University of Florida researchers, found adequate levels of the “sunshine vitamin” can help such individuals manage pain, walk, balance, and rise from sitting to standing better those with deficiencies.

The findings, published in The Clinical Journal of Pain, suggest supplements and exposure to more sunlight — which prompts the body to produce vitamin D — may be inexpensive, but effective ways to treat arthritis.

"Adequate vitamin D may be significant to improving osteoarthritis pain because it affects bone quality and protects cell function to help reduce inflammation," said lead researcher Toni L. Glover, an assistant professor in the UF College of Nursing.

“Vitamin D maintains calcium and phosphate concentration levels to keep bones strong. Increased pain due to osteoarthritis could limit physical activity, including outdoor activity, which would lead to both decreased vitamin D levels and increased obesity."

The UF researchers analyzed blood samples for vitamin D levels from 256 middle-aged and older arthritis sufferers, who also provided details on their pain and mobility. About half of the participants were obese.

The analysis found 68 of the obese individuals were vitamin D-deficient, compared to only 29 of the 130 non-obese participants were deficient —suggesting obesity is significantly associated with vitamin D deficiency.

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.

The Institute of Medicine recommends that adults get 600 international units of vitamin D per day and adults over 71 get at least 800 international units of vitamin D per day. A single eight-ounce glass of fortified milk contains about 100 international units of calcium. Foods rich in vitamin D include salmon, tuna, sardines, shrimp, mushrooms, egg yolks, fortified milk, cereals, yogurt, and orange juices.

The body also produces vitamin D through sun exposure, although it can be hard to get enough from the sun alone from the winter sun in some climates and sunscreens block the vitamin's production.

"Vitamin D is inexpensive, available over-the-counter and toxicity is fairly rare," Glover said. Older obese patients with chronic pain should discuss their vitamin D status with their primary care provider. If it's low, take a supplement and get judicious sun exposure."

This research was funded by the National Institutes of Health.