If you have rheumatoid arthritis (RA), there are two things you need to know about vitamin D. No. 1 is that vitamin D may help your immune system. No. 2 is that there is a good chance you are not getting enough of it. RA is an autoimmune system disease. This means your symptoms are caused by your body's defense system (your immune system) attacking your joints by mistake. Doctors think the cause of RA is a combination of abnormal genes you are born with and certain triggers in your environment that cause those genes to become active. Vitamin D may block some of these triggers by stabilizing your immune system. Vitamin D is also important in RA because it helps prevent osteoporosis, which is a problem for many people with RA. Why You Need Vitamin D for RA Vitamin D is called the "sunshine vitamin" because your skin produces the nutrient when you are exposed to the sun's rays. You need vitamin D to absorb calcium from your diet. You need calcium for strong, healthy bones, which are definitely important in RA. You also need vitamin D to maintain a healthy immune system. Studies show that women with higher levels of vitamin D are 30% less likely to suffer from RA. A recent study reported in The Journal of Rheumatology looked at vitamin D levels in 850 people with RA. Those who had the lowest levels of vitamin D also had the greatest number of tender joints. Why You May Not Be Getting Enough Vitamin D Vitamin D is not easy to get from your diet. There just aren't that many foods that have vitamin D. This means the vitamin D your skin makes is important. But if your RA symptoms are active, it may be hard for you to get outside in the sun. Another problem is that many people with RA need to take steroid medications. A new study done at the Albert Einstein College of Medicine in New York City found that taking steroids doubles your chances of being low in vitamin D. Doctors are not sure why this happens, but anyone who's on frequent steroids should have their vitamin D level checked. If you live in the northern half of the United States, you probably cannot make enough vitamin D in the winter. That may be one reason why people who live farther away from the equator have more risk of having autoimmune disease. What to Do As you get older, it gets harder for your skin to make vitamin D. Studies show that more than half of all Americans older than 65 are vitamin D-deficient. Your risk could be even higher if you have RA. If you don't know your vitamin D level, ask your doctor about a blood test to check it. Here are tips for getting vitamin D: Many experts now recommend trying to get 800 to 1,000 international units (IUs) of vitamin D a day. Try to get about 15 minutes of sunshine on your arms or legs (without sunscreen) several times a week. Eat more fish, like tuna, mackerel, and salmon, which are naturally high in vitamin D. Eat more foods fortified with vitamin D, like milk, orange juice, and cereal. Your doctor may recommend taking higher levels of a vitamin D supplement if your blood test shows your level is low. Some studies suggest that taking supplements in higher doses may improve RA symptoms, but more research needs to be done. Key Takeaways Vitamin D may stabilize your immune system, which could help prevent or reduce RA symptoms. Many people who are elderly, taking steroids, disabled, or live in northern parts of the United States are deficient in vitamin D. You can increase vitamin D levels with sun exposure, diet, and supplements.