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Next Diet, or the food regularly eaten, must contain all the essential nutritional elements: proteins, carbohydrates, fats and oils, vitamins, minerals, and water. If diet is consistently deficient in any of these nutrients, health is impaired and disease may result.
Proteins are made of amino acids, small units necessary for growth and tissue repair. Protein is the body's most plentiful substance except for water and, possibly, fat. Animal foods such as meat, fish, poultry, milk, and eggs are rich in protein. Good plant sources of protein are beans, peas, nuts, bread, and cereals. Combining in the diet plant sources, such as peanut butter with whole-grain bread or rice with beans, provides excellent protein. So does combining in the diet plant and animal sources such as cereal and milk or macaroni and cheese.
Carbohydrates are the main source of the body's energy. Carbohydrates account for about half of the calorie intake for most Americans and up to four fifths of the calories in diets of African and Asian peoples. Carbohydrate-rich foods are also the main dietary sources of protein for most of the world. Rice, wheat, corn, and potatoes are common rich sources of carbohydrates.
Sugars are not essential foods. They provide energy (calories) but no nutrients. For that reason sugar is called an "empty calorie" food. Occasional sweets are not harmful to a healthy, active person, but excessive sugar in the diet can lead to tooth decay when eaten between meals, especially in sticky snack foods that cling to the teeth.
Fats and oils (which are liquid fats) are a concentrated source of energy. Fats in the diet are necessary for good health. They make certain vitamins available for use in the body, they cushion vital organs, they make up part of all body cells, and they help to maintain body temperature. Fats also delay pangs of hunger because a food mixture containing fat remains longer in the stomach.
Nutritionists distinguish between different types of dietary fats. Saturated fats usually are solid in form and of animal origin. In many typical diets, meat fat is the main source. It is known that saturated fats can raise the level of cholesterol in the blood. Cholesterol is a natural waxy substance made by the body. It helps to form digestive juices and does other important work. It is present in the body no matter what is eaten. When the body cells cannot absorb any more cholesterol, any excess begins to accumulate in the walls of the blood vessels and gradually narrows them. This condition may lead to a heart attack or stroke.
Minerals are neither animal nor vegetable; they are inorganic. Almost all foods contribute to a varied intake of essential minerals. Most minerals are contaned in the diet in quantities required by the body. A major exception is iron for children under age 4 and adolescent girls and women in the childbearing years. These groups need more iron than a normal diet may provide. Iron helps to build red blood cells. It also helps the blood carry oxygen from the lungs to each body cell. Rich sources of iron are meat, especially liver, egg yolks, and dark green vegetables.
Everyone at every age needs calcium. This mineral builds bones and teeth, and it is necessary for blood clotting. The best sources are milk and hard cheese. Other dietary sources are leafy greens, nuts, and small fishes such as sardines with bones that can be eaten. Phosphorus works with calcium to make strong bones and teeth. A diet that furnishes enough protein and calcium also provides enough phosphorus. Other important minerals are sodium, potassium, iodine, magnesium, zinc, and copper.
The discovery of vitamins began early in the 20th century. It is likely that some still are undiscovered. The diet with a wide variety of foods ensures getting enough vitamins whether or not they are identified. All living things need vitamins for growth and health. The body either cannot manufacture them at all or cannot normally manufacture them in sufficient amounts, and so must absorb them from food.
Water takes an active part in many chemical reactions and is needed to carry other nutrients, to regulate body temperature, and to help eliminate wastes. In order to live, every cell in the body must be bathed in water. Water makes up about 60 percent of an adult's body weight. Requirements for water in the diet are met in many ways. For example, most fruits are more than 90 percent water.
Special diets for people with health problems should be prescribed by a physician. Many doctors refer patients to a dietitian, who draws up an individual diet plan. The typical diet contains much more salt than the body needs. Persons with high blood pressure must avoid as much salt as possible. Diabetes mellitus is another disease that requires careful meal planning. In addition to a special diet, diabetic children and some adults need medication. If diabetes develops later in life, it often can be controlled with diet alone.
Diets high in fat and cholesterol have been linked with blockage of the arteries, a common factor in heart disease and stroke. Studies show that this condition can begin in adolescence or earlier.
Some people are vegetarians; that is, they eat no meat and sometimes no eggs, cheese, or milk. Some aspects of the vegetarian diet currently are regarded as healthy alternatives to the modern diet consumed in many Western countries, which is high in animal fat and low in vegetable fiber. In nutritional terms, the vegetarian diet has been recognized as having some value in reducing the risk of heart disease, certain types of cancers, and other diet-related ailments. In general, a vegetarian diet consists of vegetables, fruits, grains, nuts, and seeds.
Vegetarians must plan their diets carefully to get balanced nutrition. Single vegetable products generally lack the essential amino acids found in animal products, but these amino acids can be included in a vegetarian diet by combining foods, such as beans and rice, that provide complementary amino acids.
