Câu hỏi:

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

Most human diets contain between 10 and 15 percent of their total calories as protein. The rest of the dietary energy comes from carbohydrates, fats, and in some people, alcohol. The proportion of calories from fats varies from 10 percent in poor communities to 40 percent or more in rich communities.

In addition to providing energy, fats have several other functions in the body. The fat-soluble vitamins, A, D, E, and K, are dissolved in fats, as their name implies. Good sources of these vitamins have high oil or fat content, and the vitamins are stored in the body’s fatty tissues. In the diet, fats cause food to remain longer in the stomach, thus increasing the feeling of fullness for some time after a meal is eaten. Fats add variety, taste, and texture to foods, which accounts for the popularity of fried foods. Fatty deposits in the body have an insulating and protective value. The curves of the human female body are due mostly to strategically located fat deposits.

Whether a certain amount of fat in the diet is essential to human health is not definitely known. When rats are fed a fat-free diet, their growth eventually ceases, their skin becomes inflamed and scaly, and their reproductive systems are damaged. Two fatty acids, linoleic and arachidonic acids, prevent these abnormalities and hence are called essential fatty acids. They also are required by a number of other animals, but their roles in human beings are debatable. Most nutritionists consider linoleic fatty acid an essential nutrient for humans.

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