Many researchers now believe that the "sunshine vitamin" may one day play a key role in preventing the development and progression of arthritis. Researchers, including scientists at Johns Hopkins under the direction of Uzma Haque, M.D., Assistant Professor of Medicine in the Department of Medicine, Division of Rheumatology at Johns Hopkins, have been looking at the effect of vitamin D on rheumatoid arthritis and osteoarthritis and the data are quite suggestive. Vitamin D is proving to be a most promising area for arthritis research.
Vitamin D is a fat-soluble vitamin that's essential for human health. Vitamin D levels are assessed with a simple blood test that measures levels of 25-hydroxy vitamin D, or 25(OH)D, the metabolite that reflects vitamin D stores; results are expressed in terms of nanograms per milliliter (ng/mL).
Although there is continuing debate over what constitutes an optimal level, most experts now agree that the level should be 30 ng/mL or higher. Yet most Americans -- up to 60% by some estimates -- have suboptimal blood levels of vitamin D. In part, that's because we spend less time outdoors and absorb less vitamin D from sunlight. However, it also may be because we don't get enough vitamin D from our diet. Only a few foods contain significant amounts of vitamin D.
It has long been recognized that vitamin D is essential to bone health because it promotes calcium absorption. Vitamin D regulates as many as 1,000 different genes, including those that weed out precancerous cells and slow the runaway reproduction of cancer cells. Vitamin D also helps maintain a healthy immune system and activates cells that fight infection, including the bacterium that causes tuberculosis.
During the past decade, there's been an explosion of research suggesting that vitamin D plays a significant role in joint health and that low levels may be a risk factor for rheumatologic conditions such as rheumatoid arthritis and osteoarthritis.
Unlike other vitamins, vitamin D is not just a simple nutrient. It's also an active steroid hormone that binds to receptors in a host of vulnerable tissues -- including the joints affected by arthritis -- and works to keep these tissues healthy. Arthritis patients may be even more likely than the general population to have low levels of vitamin D. According to a study presented at the 2008 European Union League Against Rheumatism (EULAR) meeting in Paris, nearly 75% of patients who presented at a rheumatology clinic -- including those who were subsequently diagnosed with inflammatory joint diseases, soft-tissue rheumatism, uncomplicated musculoskeletal backache, or osteoporosis -- were deficient in vitamin D.
If your D level is lower than 30 ng/mL, the parathyroid gland becomes overactive and sets in motion a process that depletes calcium from bones in order to maintain normal blood levels of calcium. This currently accepted optimal level of vitamin D is based solely on vitamin D's calcium function. However, it ignores other important functions. As we learn more about vitamin D, Dr. Haque anticipates that the optimal level will be pushed considerably higher, with an ideal range between 50 and 70 ng/mL.
