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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.
This passage is mainly to______.
选项 A、give the answers on the safe amount of vitamin D intake
B、introduce the disagreements over the Vitamin D intake and the general knowledge about Vitamin D
C、present her own questions on medicine and ask for help
D、show off her knowledge on child-care
答案B
解析 主旨大意题。文章主要介绍了关于维生素D摄入的种种争论和现有的定论。因此[B]正确。从文章中可以看出在医学界还没有就相关问题达成共识，故排除[A]；文章主题是关于维生素D的医学知识，主要是介绍权威机构在这方面所做的工作和有待解决的问题，因此并不主要提出作者自己的疑问，排除[C]；文章开头以作者自己的亲身经历为话题，引出后面的说明，因此其主旨不是炫耀其关于照顾小孩的经验，排除[D]。
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