题目内容：

阅读下面短文，根据其内容写一篇60词左右的内容概要。

You may know that vitamin C is important to your body，but do you know that vitamin D is important to your body as well? Vitamin D has a significant role in calcium homeostasis(钙稳态) and metabolism(新陈代谢). It is sometimes called the “sunshine vitamin” because it’s produced in your skin in response to sunlight.

Vitamin D can help bones and muscles grow strong and healthy. If a person is short of vitamin D，he or she may have problems like rickets(佝偻病) and osteoporosis．Rickets is mainly found in children. Osteoporosis，the thinning of bone，is a common problem as people get older. Studies in these years have found that vitamin D may also have other uses. If someone is short of vitamin D, he may have heart problems or die from some cancers.

The easiest way to get vitamin D is from sunlight. But many people worry about getting skin cancer and skin damage from the sun. Also, even skin color has an influence. Darker skinned people get less vitamin D than lighter skinned people. Older people get less vitamin D than younger people. You can also get it from foods. Some food such as cheese and egg yolks (蛋黄) have some vitamin D．But most of vitamin D in the American diet comes from food like milk with the vitamin added.

Now more doctors are testing for vitamin D in their patients. However, some doctors worry that if people take too much vitamin D, it might be bad for their body. At the same time, skin doctors tell people to be careful with strong sunlight.

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