Nutrition is the science that deals with food and how the body uses it. Food supplies energy, which people need to perform certain actions. Food also provides substances the body needs to build and repair its tissues and to regulate its organs and organ systems.
Food provides certain chemical substances needed for a person to maintain good health. These substances are called nutrients. Nutrients perform three important functions. They provide for building, repairing, or maintaining body tissues. They help regulate body processes and serve as fuel to provide energy. The body needs energy to maintain all its functions.
The amount of energy varies for every person. A person who plays sports needs more calories than someone who does little physical work. Children need more calories than their size would indicate because they are growing. Pregnant women need extra calories to provide enough nutrients for a healthy baby. The foods we eat contain thousands of different chemicals.
Our body needs only a few dozen of these chemicals in order to stay healthy. Nutrients are divided into six main groups. They are water, carbohydrates, fats, proteins, minerals, and vitamins. Water carbohydrates, fats, and proteins are called macronutrients. The body needs these four nutrients in large amounts.
Minerals and vitamins are called micronutrients. The body needs only small amounts of these nutrients. Water is the most important nutrient. Water is needed in great amounts because the body consists largely of water; 50 and 75 percent of a person’s body weight is made up of water.
The body needs water to carry out all of its life processes. Water dissolves other nutrients to carry them to all of the tissues. The body also needs water to carry away waste products and to cool itself. Adults should drink about 2 1/2 quarts of water every day. The carbohydrates, fats, and proteins have nutrients which provide energy.
Carbohydrates include all sugars and starches. They are the main source of energy for living things. There are two types of carbohydrates, simple and complex. Simple carbohydrates include sugars and have a simple molecular structure. Complex carbohydrates include starches and have a larger and more complicated molecular structure.
Fats are a source of energy. All fats are composed of an alcohol called glycerol and fatty acids. A fatty acid consists of a chain of carbon atoms. There are three types of fatty acids.
They are saturated, monounsaturated, and polysaturated. Proteins are one of the main building materials for the body. Skin, cartilage, muscle, and hair are made up of proteins. Protein also contains enzymes which speed up chemical reactions.
Cells could not function without enzymes. Proteins also serve as hormones (chemical messengers) and as antibodies (disease fighting chemicals). Proteins are large molecules made up of smaller units called amino acids. The body must have twenty amino acids. It can produce eleven of them in sufficient amounts.
The nine others are called essential amino acids. The body cannot make these amino acids. They must come from food. The best sources of protein are cheese, eggs, lean meat, fish, and milk. The proteins in these foods are called complete proteins because they contain adequate amounts of all the essential amino acids.
Cereal grains, legumes (plants of the pea family), vegetables, and nuts also supply proteins to the body. These proteins are called incomplete proteins because they do not have adequate amounts of one or more of the essential amino acids. Although the vitamins and minerals are only needed in small amounts, they are still important to the body. Minerals are needed for growth, to maintain tissues, to regulate body functions, and maintenance of body structures. Minerals are inorganic compounds.
that are not created by living things. The required minerals are calcium, magnesium, phosphorus chlorine, potassium, sodium, and sulfur. Calcium, magnesium, and phosphorus are important for the bones and the teeth. Calcium, which is mostly found in milk products, is also necessary for blood clotting. Cereals and meats provide phosphorus. Whole grain cereals, nuts, and lettuce, are good sources of magnesium.
Vitamins regulate chemical reactions by which the body converts food into energy and tissues. There are 13 vitamins. The main vitamins are A, B-1, B-2, B-12, C, D, E, and K. Vitamin A .