单选题 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 IUs 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 IUs 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 IUs 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 IUs 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 IUs 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 IUs. Some Vitamin D advocates point to the vigorous use of sunscreen as the reason studies show that so many Americans don"t get enough Vitamin 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 cod liver oil.
单选题 Which one of the following statements is TRUE according to Para. 1?
【正确答案】 C
【答案解析】[解析] 推理判断题。第一段第三句说明其第一个孩子在医生建议下多晒太阳，以加强维生素D的摄入。由此可推知C正确。第一段第三句也说明第一个孩子没有摄入任何维生素营养液，故排除A；第一段第二句说明第三个孩子摄入的是营养液，而B是指药片，故排除B；第一段第四句表明其第二个孩子摄入了200国际单位的维生素营养液，故排除D。
单选题 What can be inferred from Para. 2?
【正确答案】 C
【答案解析】[解析] 推理判断题。第二段第二句的actually a hormone表示其属于激素类。因此C正确。第二段第一句Turns out the debate about how much Vitamin D...说明关于摄入量是有争论的，故排除A；第二段第二句growing body of research表示有越来越多的这方面的研究，故排除B；第二段第二句列举了很多维生素D对人体的益处，故排除D。
单选题 Which of the following descriptions about the amount of Vitamin D intake is TRUE?
【正确答案】 D
【答案解析】[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说明过量摄入有危险，故排除C。
单选题 What can we learn from the passage?
【正确答案】 C
【答案解析】[解析] 推理判断题。最后一段倒数第二句明显指出补充维生素D的多种方法，食物如牛奶和面包中都含有强化的维生素D，故C正确。A说人们不能从食物中获取维生素D，故排除A；最后一段第三句指出过多地使用防晒产品使美国人维生素D摄入不足，故排除B；第四段最后一句说明对于儿童的摄入量有一定的建议标准，但对青少年还没有定论，故排除D。
单选题 This passage is mainly to ______.
【正确答案】 B
【答案解析】[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，因此并不是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。