人体不可缺乏的元素:维生素D

　　人体不可缺乏的元素：维生素D

　　This is the VOA Special English Health Report.

　　In recent years, research has suggested more health value from vitamin D than had once been thought.

　　Vitamin D is produced naturally in the blood. Sunlight is a major source. It is also found in some foods. These include eggs, liver and some fish. Vitamin D is also found in pills. Vitamin D helps to increase levels of calcium in the blood. It helps build strong bones and teeth. It also helps in muscle development.

　　It also appears to do more than just protect against rickets. That serious bone disease was the reason vitamin D was added to milk. Rickets is now rare in the western world. But it is still a common childhood disease in developing countries. Rickets can cause bone pain and weakness, teeth problems and muscle loss.

　　Now researchers at the Harvard School of Public Health in Boston say vitamin D might protect against multiple sclerosis, also called MS.

　　MS is a pro美国GREssive disease of the central nervous system that affects about two million people around the world. There is no cure. MS causes problems with speech and movement. The level of severity can differ from person to person. But is usually seriously disabling.

　　The study in Boston involved blood samples from more than seven million members of the American military. It found that people with higher levels of vitamin D had lower rates of MS. It found that the chance of developing MS was sixty-two percent lower among those with the highest level of vitamin D than those with the lowest level.

　　Alberto Ascherio led the study. He says vitamin D may become a future treatment for MS. But, he says first scientists must carry out a large, controlled study in which some people get vitamin D and others do not.

　　This is not the first study to show a possible relationship between vitamin D and multiple sclerosis. But it has provided the clearest evidence of a direct link.

　　The National Institutes of Health says some studies also suggest vitamin D may protect against some kinds of cancer, especially colon cancer. But it says more human studies are needed to learn if a lack of vitamin D increases the risk of cancer…or if treatment with large amounts of vitamin D could protect against the disease.

　　And that's the Special English Health Report, written by Caty Weaver. You can get transcripts of our health reports, and download audio, at voaspecialenglish.com. I'm Steve Ember.