Vitamin D is found naturally in very few foods, though some foods (like milk) are fortified with vitamin D. We can also get this vitamin through sun exposure. Unlike some vitamins that begin working in the body immediately after being consumed, vitamin D must be processed by the liver and kidneys into a form (calcitriol) that can attach to vitamin D receptors in most of the body's cells. Vitamin D promotes calcium absorption in the gut and helps with bone mineralization to keep bones strong.

The National Institutes of Health has set the recommended dietary allowance (RDA) for vitamin D to be 600 IU each day for ages 1-70. After age 70, the RDA increases to 800 IU. If you have a vitamin D deficiency, you may require supplementation. Adults who are deficient may benefit from adding 800-2,000 IU of vitamin D per day, based on body weight and vitamin D intake. Adults over 75 years of age may benefit from supplementation of 2,000-4,000 IU each day if deficient.

Hydroxychloroquine (Plaquenil) and corticosteroids are among the medications used to treat rheumatoid arthritis than can affect vitamin D absorption. If you are taking one of these drugs, your doctor should closely monitor your serum vitamin D levels regularly and may prescribe vitamin D supplementation to correct any malabsorption.

You can ask your doctor to give you a simple blood test called a total serum 25-hydroxyvitamin D test. It can tell you how deficient you might be in vitamin D. The optimal range is 25-80 ng/mL. Mild to moderate deficiency is 10-24 ng/mL, while severe deficiency is less than 10 ng/mL. Vitamin D deficiency may lead to increased autoimmunity, impaired immunity, and increased risk of colon, prostate, and breast cancer.

The best dietary sources of vitamin D are fatty fish such as salmon, trout, swordfish, mackerel, and tuna. Egg yolks and mushrooms also provide vitamin D. You also could also choose a cereal and milk (or milk alternative) fortified with vitamin D.

Just 15 minutes of exposure to the sun can give you the equivalent of 2,000-4,000 IU of vitamin D. When your skin absorbs sunlight, it is transformed into pre-vitamin D3 (cholecalciferol). It is important to note that cloud cover, air pollution, and use of sunscreen with a SPF above 15 can significantly increase the amount of time needed in the sun to achieve sufficient vitamin D supply.

Not only does vitamin D play a crucial role in the absorption of calcium, but it can stave off osteoporosis, which can be a risk for people with RA. Vitamin D has been shown to have a positive impact on fall and fracture prevention, which are at a higher risk when you have RA. It also protects those susceptible to seasonal affective disorder from becoming depressed.

Studies have linked low vitamin D levels with heart disease and heart attacks. The systemic inflammation of RA affects internal organs and increases the risk of heart attack and stroke. Managing this risk includes seeing a preventative cardiologist, eating a balanced, heart-healthy diet, maintaining a healthy weight, and quitting smoking. It may also include getting enough vitamin D.

A lack of vitamin D may play a role in chronic pain caused by a variety of conditions, though the exact link is not clearly defined. Research has indicated vitamin D deficiency may be implicated in musculoskeletal conditions, such as rheumatoid arthritis, neuropathy, migraine, and inflammation. Many doctors routinely check their patients for their levels of vitamin D and often recommend vitamin D supplements as part of a treatment plan if a deficiency is identified.

Excessive vitamin D supplementation over time can cause toxicity, which can lead to abnormal heart rhythms, kidney stones, muscle weakness, and confusion. Always speak to your health care provider before taking any vitamin supplement, including vitamin D.