Day 40 Milk and dairy products are rich in vitamin D and calcium—substances essential for building and maintaining bones

Milk and dairy products are rich in vitamin D and calcium— substances essential for building and maintaining bones. Many people therefore say that a diet rich in dairy products can help prevent osteoporosis, a disease that is linked to both environmental and genetic factors and that causes the bones to weaken significantly with age. But a long-term study of a large number of people found that those who consistently consumed dairy products throughout the years of the study have a higher rate of bone fractures than any other participants in the study. Since bone fractures are symptomatic of osteoporosis, this study result shows that a diet rich in dairy products may actually increase, rather than decrease, the risk of osteoporosis.

Write a response in which you discuss what specific evidence is needed to evaluate the argument and explain how the evidence would weaken or strengthen the argument.

五问：

（1）“this study result shows that a diet rich in dairy products may actually increase, rather than decrease, the risk of osteoporosis”是结论，其余部分是事实，值得反驳吗？

（2）同学们应该注意到：本文使用了一项调查研究作为主要论据，那么肯定应当对该论据的有效性进行驳斥。尽管我们经常对一项研究进行的时间长短以及所选样本的数量进行反驳，但是在本段中，这两点值得反驳吗？（这两点在原文中都已经被额外地强化，继续反驳会显得有些死缠烂打。）

（3）样本的选择存在这样一个问题：食用奶制品的人群可以代表所有的人吗？食用奶制品的人群是否可能具有其他方面的特点？比如：他们更有可能是自身缺钙的人群。这样的结论会如何影响样本的有效性？食用奶制品更少的人群是否更可能是那些并不缺钙、身体更好的人群？

（4）骨质疏松症一定是由缺钙导致的吗？是否还有其他原因？例如糖尿病也会引发骨质疏松。

（5）发生骨折的原因有很多，缺钙当然是其中一种，你能再罗列出其他几种可能导致骨折的原因吗？一个热衷于体育运动的群体，比如青少年，更有可能发生骨折现象，能够简单地得出这个群体缺钙的结论吗？