Research over the years has shown that maintaining adequate levels of vitamin D may have a protective effect and lower the risk of developing multiple sclerosis (MS). A number of studies have shown that people who get more sun exposure and vitamin D in their diet have a lower risk of MS. Therefore, vitamin D supplementation is considered an important modifiable environmental risk factor for development of multiple sclerosis.

Some studies suggest that for people who already have MS, vitamin D may offer some benefits. These benefits include lessening the frequency and severity of their symptoms, improving quality of life, and lengthening the time it takes to progress from relapsing-remitting multiple sclerosis to the secondary-progressive phase. But the evidence isn't conclusive. Vitamin D supplementation in people with MS appears to be safe but at high doses can lead to changes in calcium levels. More research is needed to determine whether it's truly beneficial.

Experts also need to better understand how vitamin D might affect MS. When a person has MS, his or her immune system attacks the coating that protects the nerve cells (myelin). Research suggests that a connection between vitamin D and MS could be tied to the positive effects vitamin D has on the immune system.

The connection between vitamin D and MS is strengthened by the association between sunlight and the risk of MS. The farther away from the equator a person lives, the higher the risk of MS. Sunlight is the body's most efficient source for vitamin D — suggesting that exposure to sunlight may offer protection from MS.

The Institute of Medicine recommends 600 international units (IUs) of vitamin D a day for adults up to age 70. The recommendation increases to 800 IUs a day for adults age 71 and older. The recommendation for women who are pregnant or breast-feeding is 600 IUs per day. However, the Institute of Medicine recommends avoiding taking more than 4,000 IUs a day.

Research studies have indicated that taking 400 IUs or more of vitamin D per day significantly decreases the risk of MS in women.

If you are diagnosed with vitamin D deficiency, it may be appropriate to use up to 50,000 IUs weekly for up to three months until your vitamin D levels become normal, and then switch to a maintenance dose. The maintenance dose varies, but is usually between 2,000 and 5,000 IU daily.

Very large doses of vitamin D over an extended period can result in toxicity. Signs and symptoms include nausea, vomiting, constipation, poor appetite, weakness and weight loss. In addition, vitamin D toxicity can lead to elevated levels of calcium in your blood, which can result in kidney stones.

If you're considering vitamin D to reduce your risk of or help manage multiple sclerosis, talk with your doctor about what's both safe and helpful for you.