来自医学博士Jerry W. Swanson的回答。
A study conducted by researchers at the University of Oxford and another conducted at the New Jersey Medical School have suggested that maintaining adequate levels of vitamin D may have a protective effect and lower the risk of developing multiple sclerosis (MS). Another study conducted at Maastricht University in the Netherlands and others suggest that for people who already have MS, vitamin D may lessen the frequency and severity of their symptoms. More research is needed to assess these findings.
When a person has MS, his or her immune system attacks the coating that protects the nerve cells. 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 link 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.
Screening for vitamin D deficiency is important for African-Americans and other ethnic groups with dark skin, due to decreased natural production of vitamin D from sun exposure.
The Institute of Medicine recommends 600 international units (IUs) of vitamin D a day for adults ages 19 to 70. The recommendation increases to 800 IUs a day for adults age 71 and older.
Some doctors question whether these levels are adequate and think that getting more vitamin D would benefit many people. However, the Institute of Medicine recommends that adults avoid taking more than 4,000 IUs a day.
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.
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 concerned that you're getting too little — or too much — vitamin D, talk with your doctor about what's right for you.
中文翻译：
本文地址：http://www.wjbb.com/know/605
原文出处：http://www.mayoclinic.org/diseases-conditions/multiple-sclerosis/expert-answers/vitamin-d-and-ms/faq-20058258
