Carbohydrates Carbohydrates are compounds that come from plants and contain carbon, hydrogen, and oxygen. These nutrients supply energy, which all living things need. Carbohydrates are the body s most important source of fuel because they can be used right away or stored for later, and it takes little effort for the body to release their energy. There are 2 types of carbohydrates: Complex carbohydrates give your body lasting energy. They include starches, glycogen and fiber. Starches are found in grains and root vegetables. Starches give the body an easy way to get energy. Glycogen is a special form of starch that can be stored in the liver and muscles, and used as a reserve energy source. Fiber is found in vegetables, fruits, beans, peas and grains. Fiber helps move waste out of the body and can help prevent colon cancer. Foods that are good sources of complex carbohydrates include vegetables, fruits, beans, wheat, corn, rice and whole-grain breads, pastas and cereals. Foods with complex carbohydrates also provide other important nutrients, such as vitamins and minerals. Simple carbohydrates are sugars that dissolve in water and taste sweet. They include sucrose (table sugar), fructose (fruit sugar), lactose (milk sugar) and maltose (grain sugar). The body needs to digest sugar before it can use that sugar to meet its energy needs. Examples of foods that contain simple carbohydrates include candy, soft drinks, cake, pastries and cookies. All carbohydrates are eventually turned into glucose, a simple form of sugar that s the basic source of energy the body uses each day. The glycogen stored in the liver and muscles is turned into glucose when the body needs it. The body can also turn fats and proteins into glucose, but it does this only when the energy from carbohydrates is used up. When people don t eat enough complex carbohydrates they don t have enough energy and feel tired and less alert. They also may not get enough fiber. Eating too many simple carbohydrates can lead to weight gain. Carbohydrates are turned to energy as the body needs it, so excess carbohydrates are stored as fat. People may not eat enough healthy complex carbohydrates if they fill up on simple carbohydrate foods.
Fats All cells contain some fat, but the body fat most people think of is the type meant to conserve energy for times when food is scarce. This fat is stored throughout the body in expandable cells. The body needs fat to: Protect against cold Provide energy for muscles Protect internal organs Fats in the diet are important for healthy skin and hair, normal growth and nerve function. Fat also helps the body make certain types of hormones and absorb vitamins. Cholesterol is a waxy fat made by the body. It is also found in foods that contain animal fat, such as meats and whole milk. Cholesterol is an essential part of cell membranes, but high levels of it in the blood can lead to heart disease. There are 4 main types of fats to know about: Saturated fats are found in largest amounts in animal fats from meat and dairy products, and in a few vegetable oils, such as coconut and palm kernel oils. These fats are solid at room temperature. Eating too much saturated fat raises harmful blood cholesterol levels in many people and increases their risk for heart disease. Monounsaturated fats are found in olive, peanut and canola oil, as well as nuts and avocados. These fats are liquid at room temperature. They have a good effect on cholesterol levels. Polyunsaturated fats are found mainly in safflower, sunflower, corn, soybean and cottonseed oils, and in fatty fish such as salmon and tuna. These fats are liquid at room temperature. Like monounsaturated fats, they can have good effects on cholesterol. Trans fats are found in most margarines, vegetable shortenings, partially hydrogenated vegetable oil, deep-fried chips, and many fast foods and commercial baked goods. They are solid or semi-solid at room temperature. Trans fats are not a natural type of fat. They were developed to make shipping and storage of foods easier. Trans fats contribute to harmful cholesterol levels. They are also thought to play a role in heart disease, stroke and diabetes. Only 25 35% of teens total calories each day should come from fats. The healthiest sources are fish, nuts and vegetable oils, because they contain unsaturated fat. Lean meats and low-fat dairy products can also be healthier choices. It s best to avoid foods that contain trans fats.
Proteins Proteins are made up of amino acids that the body uses to make skin, muscle and bone. Proteins are needed to: Build and replace cells Repair damaged tissues Make hormones and the antibodies that help people fight disease Help keep body fluids balanced Proteins are found in many foods, but are highest in animal products such as meat, poultry, fish, eggs and dairy. Other high-protein foods include nuts (including nut butters), seeds, beans, peas, tofu and other soybean products. Lower amounts of protein are found in most fruits, vegetables and grains. The body needs 20 amino acids for good health. Of these, 11 can be made by the body itself. The other 9 are called essential amino acids, because it s essential to get them from the foods you eat. Because the body can t store amino acids, it s important to eat some protein almost every day. A food that has all 9 essential amino acids is called a complete protein. Almost all proteins from animal sources are complete. People can also combine sources of plant proteins to be sure they get the essential amino acids. For example, beans and rice, a common meal throughout the world, form a complete protein when eaten together. Eating too much or too little protein can be unhealthy. Not getting enough protein can affect development of bones and muscles, and cause problems with skin tone. But most Americans eat more protein than the body needs. Excess proteins can be burned for energy when the energy from fats and carbohydrates is gone, but they won t build more or stronger muscles. In fact, extra protein can lead to loss of calcium and may make liver or kidney disease worse. Eating large amounts of protein can also add to weight gain, because many foods high in protein are also high in fats. This can increase the risk of high blood pressure, high cholesterol, heart disease and diabetes.
Vitamins Vitamins are compounds that help the body turn food into energy and body tissues. They help control digestion, growth and how fast the body uses food. They help make hormones, heal wounds and keep nerves working. Vitamins are fragile nutrients. They can be destroyed if a food is stored too long, cooked too much, exposed to air or even soaked in water. But only small amounts of vitamins are needed to keep the body working well. There are 2 types of vitamins: Fat-soluble vitamins can be stored in the liver and fatty tissues until the body needs them. So they do not need to be eaten every day. They include vitamins A, D, E and K. Vitamin A is important for healthy skin and strong bones. Vitamin D is needed for the body to use calcium. Vitamin E helps maintain cell membranes. Vitamin K is needed for blood to clot. Water-soluble vitamins cannot be stored by the body, so they must be eaten every day. They include vitamin C and the B vitamins. Vitamin C helps maintain ligaments, tendons and other tissues. Vitamin Bl (thiamine) helps the body change starches and sugars into energy. Vitamin B2 (riboflavin) supports the chemical reactions that allow the body to use food. Vitamin B3 (niacin) is needed by cells to release energy from carbohydrates. Vitamins B5, B6 and B7 support chemical reactions needed for growth. Vitamin B9 (folic acid) and Vitamin B12 are needed to form red blood cells and keep the nervous system healthy. Vitamin D is made by the body through exposure to sunlight. It s the only vitamin that can be made by the body. The rest must come from food. Leafy green vegetables and yellow vegetables are very good sources of vitamins A and B. Oranges, grapefruit, lemons, limes and green chilies are excellent sources of vitamin C. Lack of vitamins can cause a wide range of health problems: Lack of vitamin C can lead to scurvy, a disease that causes loss of teeth, bleeding gums, muscle pain and internal bleeding. Lack of certain B vitamins can cause nerve disorders and anemia. Lack of vitamin D can lead to rickets, a disease that causes stunted growth, muscle cramps, and bone pain. These diseases are rarely seen in the United States, but are serious in other parts of the world.
Minerals Minerals are compounds that aren t created by living things. About 60 different minerals enter the human body, either dissolved in water or from eating plants and animals that contain them. About 25 of these play specific and important roles in health. Minerals help control how the body uses food and are important for the growth and health of body structures. For example: Calcium and magnesium are needed to build healthy bones and teeth. Iron is important for hemoglobin, the molecule that carries oxygen in red blood cells. Potassium and sodium work together to help the nerves, muscles and kidneys function well, and also help maintain fluid balance in the body. Copper helps the body use the iron for making hemoglobin. Manganese and zinc help control chemical reactions in the body. Minerals are found in almost all foods. Vegetables, fruits and grain products are particularly good sources. Eating a balanced diet with a variety of foods can help you get all the minerals you need for good health. Lack of minerals can affect all body systems including the bones, heart, lungs and reproductive organs. The effects on the body are directly related to the type of mineral missing from the diet. For example, iron-deficiency anemia, which is fairly common in teen girls, results in a decrease in the number of red blood cells. Not getting enough calcium keeps bones from developing properly and results in brittle bones later in life. Getting too much of some minerals may be harmful. For example, carbonated sodas contain phosphates that can keep your body from using calcium and weaken your bones, and high levels of sodium are linked to high blood pressure. Too much of any one mineral may upset the balance and function of other minerals in the body. Excess mineral intake can reduce a person s ability to perform physical tasks and add to health problems such as weak bones and nerve disease.
Water Water is the one nutrient every living thing must have. Water is so important your body can t live for more than a few days without it. Every cell in the body requires water to stay alive, and water usually makes up 50% to 75% of a person s body weight. Water does many jobs in the body: It helps blood flow, carrying nutrients and oxygen to the body s cells and removing cell wastes. It helps with digestion and is part of many of the chemical reactions that occur in the body. It helps keep a steady body temperature. Water distributes heat and cools the body as it evaporates from the skin. Under normal conditions, the body loses about a pint of water a day through perspiration. But during exercise in hot weather, a person can lose 3 gallons in a single day. It removes wastes from the body, mostly through urine, but also through feces. The lungs also give off water when you breathe out. This is why you can see your breath in cold weather. Nearly all foods contain water. Some are up to 90% water. Beverages, fruits and vegetables are major sources of water in the diet. The body loses about 1 quart of water each day. Experts recommend drinking 8 or more glasses of water daily, rather than drinking soda, coffee, juice or other beverages, to replace body fluids. Not drinking enough water can hurt all of the body s systems. For example, without enough water, the body can t use water-soluble vitamins, carry oxygen in the blood, or control its temperature. When the amount of water leaving the body is greater than the amount coming in, dehydration a dangerous lack of water occurs. Dehydration can be caused by sweating, illness (especially diarrhea or vomiting), injury (such as severe burns) or not drinking enough fluids. Thirst is a signal that the body is becoming dehydrated. A person who s dehydrated may have a dry mouth and feel flushed, very tired, light headed or clumsy. Simply drinking fluids can often correct these milder symptoms. But if dehydration continues, it can lead to confusion, faster pulse, lower blood pressure, fever, loss of consciousness and even death. This is why drinking fluids throughout the day is important. It s especially important to drink enough water before, during and after physical activity, or when the weather is hot. It s possible to drink too much water, but this is very rare. A person would have to drink an enormous amount of water all at the same time to suffer any ill effects. Most people do not drink enough water.