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  3. The Action of Vitamin D I, a mother of two girls, gave birth to a third girl one month ago. The pediatrician recommended a l

The Action of Vitamin D I, a mother of two girls, gave birth to a third girl one month ago. The pediatrician recommended a l

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问题                         The Action of Vitamin D
    I, a mother of two girls, gave birth to a third girl one month ago. The pediatrician recommended a liquid multivitamin that contains 400 international units (IUs) of Vitamin D for the new born baby, which confused me a lot. When my first girl, who is now 4, was born, the doctor told us to simply get her out in the sun from time to time to let her body produce Vitamin D. When our second child was born two years ago, we were told to give her a multivitamin that had 200 lUs of Vitamin D. So there is a big change, and what do we really know about its risks and benefits?
    Turns out the debate about how much Vitamin D we need has intensified over the past 10 years. One part of the discourse focuses on the growing body of research that point to numerous health benefits of the chemical (actually a hormone) ; it can help prevent rickets in children and severe bone loss in adults and potentially lowers the risk of multiple sclerosis, juvenile diabetes, cancer, heart disease, colds and influenza.
    Amid all this new evidence, the Institute of Medicine (IOM) has assembled a panel of experts to reevaluate just how much Vitamin D we really need and can safely tolerate. Current IOM recommendations, set in 1997, are 200 Ills a day from birth to age 50 and a bit more after that. The upper limit of safety, according to the institute, is 2, 000 lUs daily—too much can lead to, among other things, nausea and kidney stones—yet some vitamin D proponents are pushing for up to 4,000 lUs a day for adults.
    The IOM review won’t be completed until May 2010. In the meantime, Dr. Frank Greer, chairman of the nutrition committee at the American Academy of Pediatrics, is confident that the academy’s new guideline of 400 IDs is enough for kids under 2. But, he wonders, "what about adolescents? Do they need 800?" That remains to be seen.
    In addition to the question of how much Vitamin D, there is debate over the best way to get it. About 10 to 15 minutes spent outside in full sun will give a fair-skinned person dressed only in his skivvies 10,000 to 20,000 lUs. Some vitamin D advocates point to the vigorous use of sunscreen as the reason studies show that so many Americans don’t get enough D. But we don’t want taking advantage of the potential benefits of Vitamin D to mean increased risk of contracting skin cancer. In addition to supplements, there are foods that naturally contain Vitamin D (salmon, egg yolks, liver) and others that are fortified with it (milk, cereals, juices, breads). And, of course, there is always codliver oil.
Which of the following descriptions about the amount of Vitamin D intake is true?
选项 A、The upper limit of Vitamin D intake for adults is 400 lUs.
B、It is dangerous for adults to take 2,000 lUs Vitamin D daily.
C、An overdose of Vitamin D does not necessarily result in diseases.
D、For people under 50, it is safe to take 200 lUs Vitamin D daily.
答案D
解析 事实细节题。由题干关键词Vitamin D intake定位到第三段第二句…recommendations．．．are 200 IUs a day from birth to age 50 and a bit more after that．．．可知，对于50岁以下及略高于50岁的人群设定的建议安全标准是每天200国际单位。因此[D]正确。第三段最后一句说明其上限是2000 IUs，故排除[A]和[B]；第三段最后一句too much can lead to，among other things，nausea and kidney stones说明过量摄人有危险，故排除[C]。
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