The FDA approves of 200 IU for 19-50 year olds; 400 IU for people over 50. Most vitamin pills contain 400 IU of vitamin D.

FDA推荐19-50岁的人摄入200国际单位，50岁以上摄入400国际单位。大部分维生素片含有400国际单位的维生素D。

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Some suggest as much as 10, 000 IU --currently the tolerable upper intake daily.

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However, he said, there's no harm in taking a 200-IU dose of vitamin D because it's difficult to get the recommended daily amount of 600 IUs from food alone for children and adults up to age 70.

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The IOF estimated that doses of 800 to 1, 000 IU (20-25 mcg) or higher may be required in older adults to prevent fractures and falls but stated that more research is necessary.

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