单选题 Imagine eating everything delicious you want with none of the fat. That would be great, wouldn"t it?
New "fake fat" products appeared on store shelves in the United States recently, but not everyone is happy about it. Makers of the products, which contain a compound called olestra, say food manufacturers can now eliminate fat from certain foods. Critics, however, say the new compound can rob the body of essential vitamins and nutrients and can also cause unpleasant side effects in some people. So it"s up to consumers to decide whether the new fat-free products taste good enough to keep eating.
Chemists discovered olestra in the late 1960s, when they were searching for a fat that could be digested by infants more easily. Instead of finding the desired fat, the researchers created a fat that can"t be digested at all.
Normally, special chemicals in the intestines (肠) "grab" molecules of regular fat and break them down so they can be used by the body. A molecule of regular fat is made up of three molecules of substances called fatty acids. The fatty acids are absorbed by the intestines and bring with them the essential vitamins A, D, E, and K. When fat molecules are present in the intestines with any of those vitamins, the vitamins attach to the molecules and are carried into the bloodstream.
Olestra, which is made from six to eight molecules of fatty acids, is too large for the intestines to absorb. It just slides unchanged through the intestines without being broken down. Manufacturers say it"s that ability to slide unchanged through the intestines that make olestra so valuable as a fat substitute. It provides consumers with the taste of regular fat without any bad effects on the body. But critics say olestra can prevent vitamins A, D, E, and K from being absorbed. It can also prevent the absorption of carotenoids (类胡萝卜素), compounds that may reduce the risk of cancer, heart disease, etc. Manufacturers are adding vitamins A, D, E, and K as well as carotenoids to their products now. Even so, some nutritionists are still concerned that people might eat unlimited amounts of food made with the fat substitute without worrying about how many calories they are consuming.
单选题 We learn from the passage that olestra is a substance that ______.
【正确答案】 D
【答案解析】[解析] 细节推断题。文章第一段先提出Imagine eating everything delicious you want with none of the fat. That would be great, wouldn"t it? (想象人们能吃到的东西既美味可口又不含脂肪会是多么好。)第二段指出:目前新型“代脂肪”产品已经在美国销售,这种产品的制造商说,这种产品包含一种叫olestra的化合物,可以用这种化合物代替某些食品中的脂肪。由此推断olestra应该是一种既好吃又不会使人发胖的脂肪替代物,因此正确答案为D。
单选题 The result of the search for an easily digestible fat turned out to be ______.
【正确答案】 D
【答案解析】[解析] 细节推断题。根据第三段最后一句Instead of finding the desired fat, the researchers created a fat that can"t be digested at all可知,olestra的发现出乎意料,D为正确答案。
单选题 Olestra is different from ordinary fats in that ______.
【正确答案】 A
【答案解析】[解析] 细节推断题。根据第五段第一句Olestra is too large for the intestines to absorb可知,olestra太大,肠道无法吸收。
单选题 What is a possible negative effect of olestra according to some critics?
【正确答案】 C
【答案解析】[解析] 细节推断题。根据第五段第五句和第六句可知:olestra不能让维生素A、维生素D、维生素E得到吸收,也会阻止可以降低癌症、心脏病等疾病发生的类胡萝卜素的吸收。因此正确答案为C。
单选题 Why are nutritionists concerned about adding vitamins to olestra?
【正确答案】 B
【答案解析】[解析] 事实细节题。文章最后一句中的people might eat unlimited amounts of food made with the fat substitute without worrying about how many calories they are consuming指出,营养学家担心,人们会因为不用担心此类食品中所包含的卡路里而无限制地吃。与此意相符的选项为B。