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A healthy diet is essential for maintaining a healthy body and a healthy lifestyle. Though some doctors and health experts disagree on some components of a healthy diet, other parts are almost universally recognized. For example, all agree that a healthy diet includes necessary nutrients - ingredients that help keep bodies strong and healthy. Human bodies need more than 50 different kinds of nutrients, including vitamins, minerals, water, and fiber. Vitamins are natural substances found in plants and animals. A body cannot make its own vitamins, so it must get them from food. Vitamins do not supply energy. However, they are useful substances that the body needs. Vitamin A, for example, helps eyes see better. Vitamin B develops protein needed in muscle growth. Vitamin C helps support the healing process for certain illnesses. Finally, Vitamin D helps strengthen teeth and bones Minerals help balance bodily fluids, such as blood and water. They are also an important part of the iron in blood. There are seven major minerals that bodies need in large amounts, and ten minor, or trace, minerals, which bodies need in smaller amounts. Scientists are still studying many minerals, such as nickel and cobalt, to try to understand exactly how they affect the human body. Some people do not include water as a nutrient, but it is vital for a healthy body to function properly. Humans can live for several days without food, but only for two or three days without water. People who play sports or exercise a lot often fail to drink enough water. This can cause their muscles to become overly tired. If not enough water is taken in during very strenuous exercise, death may in fact result. Scientists have learned much about the importance of fiber in recent years. They now say that many people do not get enough fiber in their diets. The average many people should eat between 30 and 40 grams of fiber each day, twice as much as the average person currently gets. Though fiber is not digested or absorbed, it helps rid the body of waste products. Fiber helps control weight and maintain normal levels of important substances such as cholesterol and blood sugar. Fiber is found in whole-grain breads and cereals, as well as nuts, beans, fruits, and vegetables. There are several different kinds of fiber, and they each help in different ways. Two kinds of fiber, called pectins and gums, are needed to help control body fats, cholesterol, and carbohydrates (a type of nutrient that produces energy). Apples, cranberries, and cherries are good sources of pectin. Oatmeal and legumes are good s general, fresh fruits and raw vegetables provide more fiber than peeled fruits and cooked vegetables. According to dieticians, two servings of vegetables and two servings of whole grains (like whole wheat bread) each day will provide enough fiber for most adults. In summary, recommendations for a healthy diet include drinking lots of liquids while eating fiber from a wide variety of foods. This way, the body will not be getting too much of one kind of fiber and too little of another kind. If a person is not eating enough fiber now, it is best to change one's diet gradually. Above all, experts warn, do not depend on getting fiber from pills or tablets. A whole bottle would need to be consumed to see any benefit.
10. The author's tone in this passage could best be described as ____
