Understanding Nutrients PDF

Understanding Nutrients MAIN IDEA​ Nutrients are important to keeping you healthy. Imagine that you’re riding in a car, and it suddenly runs out of gas. The car will stop, because it can’t run without fuel. Your body is the same way, but it gets its fuel from food. Your body is always using energy,...

Understanding Nutrients MAIN IDEA​ Nutrients are important to keeping you healthy. Imagine that you’re riding in a car, and it suddenly runs out of gas. The car will stop, because it can’t run without fuel. Your body is the same way, but it gets its fuel from food. Your body is always using energy, even while you sleep. Nutrients come in two types. One type gives you the energy you need for work and play. The other type of nutrient provides the building blocks needed to grow and to repair your body. Since different foods contain different nutrients, you need to eat a variety of foods each day. Eating a variety of foods can provide all of the nutrients that a person needs. Some people may prefer to eat only certain foods. These people are at risk for a nutrient deficiency. This condition is rare in industrialized countries such as the U.S. It can cause numerous health problems. Learning about nutrients, and nutrition can help you make more healthful choices about the foods you eat. Scientists have identified more than 40 nutrients. However, they all can be grouped into six main classes: proteins, carbohydrates, fats, vitamins, minerals, and water. Each of these nutrients plays an important role in keeping you healthy. Proteins Proteins help your body heal, grow, and develop. Foods containing protein also aid in the repair of tissues. Proteins are made of chemical building blocks called amino acids. Different foods contain different amino acids. Foods such as meat, fish, eggs, dairy products, and soybeans provide all the amino acids your body needs. They are called complete proteins. These foods are good sources of protein. Most plant foods, however, are missing at least one amino acid. A person who follows a vegetarian diet may need to combine certain plant foods, such as beans and rice to gain all the needed amino acids. Eating a wide variety of plant foods should give you all the amino acids you need. READING CHECK Identify​ What is the basic substance that makes up proteins? Carbohydrates What do a steamy plate of spaghetti and a ripe peach have in common? Both foods contain large amounts of carbohydrates​. ​Carbohydrates are made of sugar molecules. They are your body’s main source of energy. Your body needs carbohydrates to use as energy throughout the day and even during the night. As you sleep, your body continues to use energy. About 45 to 65 percent of your daily energy needs some come from carbohydrates. Two types of carbohydrates are found in foods: simple and complex. ​Simple​ carbohydrates are sugars. They occur naturally in foods like fruit, milk, and honey. Sugars may also be added when foods are processed. Sugars are used by the body for energy. Any sugars that are not used are stored as body fat. ​Complex​ carbohydrates are starches, which are made up of long chains of sugar linked together. Complex carbohydrates are found in foods such as potatoes, seeds, and whole-grain cereals. Your body cannot use these nutrients directly. First, it must break them down through the process of ​digestion​. You’ll learn more about digestion in a later chapter. The sugars that occur naturally in foods, such as fruit, are a healthier choice than those found in processed foods, such as cookies. As well as containing sugars, fruit also contains high amounts of fiber. In general, foods that are high in sugar tend to be low in other nutrients. Another type of complex carbohydrate, fiber, cannot be digested. Fiber cannot be used for energy, but it is still important to your health. It carries wastes out of your body. Eating high-fiber foods can lower your risk of heart disease and some types of cancer. Fats You may hear that you should avoid foods containing ​fats.​ While it is important to reduce the amounts of foods you eat that are high in fat, your body needs some fat to function properly. Your body uses fats to build and maintain your cell membranes. These nutrients also carry certain vitamins in your bloodstream. Additionally, the fats in the foods you eat help you feel full after a meal. Not all fats are the same, however. Foods like butter, cheese, and many meats are high in saturated fats​,​ which​ ​are usually solid at room temperature. Over time, eating too much of these fats can increase your risk of health problems such as heart disease. The same is true of trans fatty acids or trans fats​,​ which start off as liquid oils and are made solid through processing.​ ​Stick margarine is one example. However, unsaturated fats​,​ which remain liquid at room temperature, can actually lower the risk of heart disease. These fats come mainly from plant foods, such as olive oil, nuts, and avocados. You probably have heard of cholesterol. Your body makes two kinds of cholesterol. HDL cholesterol protects against heart disease. LDL cholesterol sticks to the walls of blood vessels, which can lead to heart disease. Eating foods high in saturated fats can raise blood levels of LDL cholesterol. Dietary sources of cholesterol include meat, eggs, some seafood, whole or reduced-fat milk, many cheeses, and butter. READING CHECK Compare and Contrast​ What is the difference between saturated and unsaturated fats? Vitamins and Minerals Two other kinds of nutrients that the body needs are vitamins and minerals. Some vitamins help your body fight disease. Others help your body produce energy. Your body uses only small amounts of minerals, but they are essential to your health. Minerals help to regulate body functions. The table below shows how your body uses several important vitamins and minerals. Some vitamins, such as vitamins C and B, are ​water-soluble.​ This means that they dissolve in water. Your body can’t store these vitamins, so it needs a fresh supply of them each day. ​Fat-soluble ​vitamins, such as vitamins A and D, dissolve in fat. Your body can store these vitamins until they needed. How can you make sure you are getting enough vitamins and minerals? The best way is to eat a variety of foods. The table below shows which foods are good sources of some important vitamins and minerals. Taking vitamin supplements can also help, but they are not a replacement for healthy eating. Water Water is essential to every body function you have. In fact, a person can live for only about a week without it. Your body uses water to carry other nutrients to your cells. Water also helps with digestion, removes waste, and cools you off. Teen girls should drink about nine cups of water per day and teen boys should drink about 13 cups of water each day. To make sure your body is getting enough water, drink with your meals. You can also get water from many foods, such as fruits and vegetables, and from beverages such as milk. Beverages containing caffeine cause the body to lose water. These beverages, such as coffee, some teas, and cola drinks should be used only in moderation. If you are very active, you may need to drink more water. Your body loses water when you sweat during hot weather or when exercising. At these times, you will need to drink extra water to meet your body’s needs. READING CHECK Explain​ Why is water important for your body?