本篇阅读材料“研究表明每天两瓶含糖饮料或使味蕾变迟钝”选自《卫报》（原文标题：Two sugary drinks a day can dull taste buds, study claims 2011.6.9）。

　　Consuming just two sugary drinks a day can dull the taste buds and lead to cravings for high-calorie food, a study claims.
　　The research suggests that within a month those who drink sugary beverages are left with a dulled sensitivity to sweet tastes. This leads to an increased preference for high-calorie and sugar-laden foods, creating a "vicious cycle" as consumers look for their next treat.
　　Those who do not have a sweet tooth are particularly at risk of developing one after drinking sugary beverages, even if they are slim and active.
　　Experts who carried out the research at the universities of Bristol and Bangor expressed surprise at how quickly tastes could be dulled by exposure to sweet drinks. Lucy Donaldson, of the University of Bristol, said: "We have known for some time that the way we perceive different tastes can change under different circumstances. Finding that two sweet drinks a day over a short time can dramatically change taste was a real surprise."
　　In the trial lean and obese people rated their perception and enjoyment of sweet and salty tastes. The obese participants tended to rate identical drinks as less sweet than the lean ones did.
　　The experts then recruited only lean people who did not usually consume sugary drinks. Their sensitivity to sweet drinks was tested and they were asked to consume a sugary drink twice a day. A month later, when they were re-tested, their sensitivity to sweet tastes and conscious enjoyment of them had dulled.
　　Dr Hans-Peter Kubis, of the University of Bangor, said the dulling of tastebuds can lead to a "vicious cycle" as consumers of sugary drinks tend to more sweet and calorie-laden food to compensate.
　　He said: "This has serious implications for public health. This research shows how little sweet food stuffs are required to actually change your taste perceptions, and how powerful sweet-tasting products are.
　　"We are heading for a health disaster with rising obesity levels and the increasing incidence of type 2 diabetes. From our research it is clear to see how this situation may have created a cycle of sweet food and drink consumption. As taste satisfaction levels drop; the more sweet foods are consumed, contributing to these problems."

　　【重点单词及短语】
　　taste bud 味蕾
　　craving for 对……的渴望
　　preference for 偏爱……；优先选择
　　sugar-laden adj. 富含糖分的
　　sweet tooth 喜好甜食
　　at risk of 冒……之危险
　　perceive v. 察觉；理解；认知
　　lean adj. 瘦的；贫乏的 v. 倾斜；倚靠；倾向
　　obese adj. 肥胖的，过胖的
　　compensate v. 补偿，赔偿
　　head for 前往；出发；取向于

　　Question time:
　　1. What if we are left with a dulled sensitivity to sweet tastes?
　　2. According to the research, what's the consequence of a dulled sensitivity to sweet tastes?