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Nutrition
Nutrion begins with foods. The study of nutrition involves everything that the body does
with food in order to live, like function, and grow. Foods that are eaten regularly make a diet.
Although were you live and how you eat play a major part in your dietary habits, food choices
vary from person to person. What people eat affects their health and how they live. Plants make
their own food from, water, and air. People can't make their own food but eat plants, and meats to
survive. The body's most important need is for energy. To get energy it needs food as a fuel and
oxygen to burn it. The amount of energy food produces is called calories. A food calorie, is the
amount of heat required to raise the temperature of (2.2 pounds) of water 1 degree Celsius (1.8
degrees Fahrenheit).
The body changes the calories in food into energy, which is very nesscary for the little
things like blinking an eye to running a race. Energy is also used for the growing process, for
rebuilding damaged cells, and for regulating the body. The number of calories needed each day
depends on how much energy your body uses. An active kid can need more calories than an
adult who works at a desk. The body needs more calories in cold weather to stay at an even
temperature.
If a person consumes more food than required to meet the body's needs, the extra
calories become fat . That causes weight gain. Eating too little causes weight loss because the fat
is used for energy. One pound of stored fat has almost 3,500 calories.
If weight loss is desirable, the best way to lose weight is by eating less of high-calorie foods
and getting more exercise.Usually for most people a safe limit for losing weight is 2 pounds a
week. Quick and easy weight-loss diets are fads ;because most are unbalanced, puting emphasis
on one kind of food and excludeing others. To function, humans must have nutrients. The most
important nutrients for people are proteins, carbohydrates, fats and oils, minerals, vitamins, and
water.
Proteins are made up of amino acids, small units necessary for growth and tissue repair.
Protein is the body's most abundant substance except for water and, maybe, 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 plant sources, such as peanut butter with whole-grain bread or rice with beans,
provides excellent protein. So does combining plant and animal sources such as cereal and milk
or macaroni and cheese.
Starches and sugars are carbohydrates, the main source of the body's energy.
Carbohydrates account for about half of the calorie intake for most Americans and four fifths of
the calories in diets of African and Asian people. Foods rich in carbohydrate are also the main
source of protein for most of the world. Rice, wheat, corn, and potatoes are common rich sources
of carbohydrates.
Sugars aren't essential foods. They provide energy but no nutrients. Because of that
sugar is called an "empty calorie" food. Occasional sugars aren't harmful to a healthy, but to
much sugar can cause tooth decay when eaten between meals, especially sticky snacks that
stick to the teeth.
Fats and oils are a concentrated source of energy. Fats in the diet are a must for good
health. They make certain types of vitamins available for use in the body, they provide a cushion
for vital organs, they make up part of all body cells, and they help to maintain body temperature.
Fats also slow aches of hunger because a food mixture containing fat remains longer in the
stomach.
Nutritionists classify different types of dietary fats, or fats in food. Saturated fats usually
are solid and come from animals . In many standard diets, fat from meat is the main source. It is
a fact that saturated fats can raise the level of cholesterol in the blood. Cholesterol is a waxy
substance made by the body. It helps to form digestive juices and does other important work. It is
always in the body no matter what is eaten. When the body cells can't absorb any more
cholesterol, any excess begins to collect in the walls of the blood vessels and gradually narrows
them. This may lead to a heart attack or stroke.
Minerals are
neither animal or vegetable; they are inorganic. Almost all foods contribute to a varied intake of
essential minerals. Most minerals are easy to gain in quantities required by the body. A major
exception is iron for children under age 4 and teen girls and women in the childbearing years.
These people need more iron than a normal diet may give. 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
essential for blood clotting. The best sources are milk and hard cheese. Others are leafy greens,
nuts, and small fishes like sardines with bones that can be eaten.
Phosphorus works with calcium to make strong bones and teeth. A diet that provide 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's likely that some vitamins
still are undiscovered. Eating a wide variety of foods ensures getting enough vitamin. All living
things need vitamins for growth and health. The body either cannot produce them at all or cannot
normally produce them in needed amounts, and must absorb them from food. Each vitamin has
specific roles. Many reactions in the body require several vitamins, and the lack or excess of any
one can interfere with the function of another.
Four vitamins A, D, E, and K are called the fat-soluble vitamins. They are digested and
absorbed with the help of fats that are in the diet.
Vitamin A is needed for strong bones, good vision, and healthy skin. It's found in dark green
and yellow fruits and vegetables.
Vitamin D is essential for children because it helps calcium and phosphorus to form straight,
strong bones and teeth. With sunlight on the skin, the body can produce its own vitamin D.
Babies and young children often need vitamin D supplement.
Vitamin E helps to protect vitamin A and red blood cells. It's found in a wide variety of foods,
and almost everyone gets enough.
Vitamin K is one vitamin that is made in the human body by bacteria that live in the intestinal
tract. Small amounts are found in the green leaves of spinach, kale, cabbage, and cauliflower and
also in pork liver.
Fat-soluble vitamins can be stored in the body for long periods. They are stored mostly in the
fatty tissue and in the liver.
The vitamin B group of several vitamins helps to maintain healthy skin and a nervous
system. B vitamins also help to convert carbohydrates into energy. Vitamin C is needed for
building the connective tissue that holds body cells together. Vitamin C is essential for healthy
teeth, gums, and blood vessels. It also helps the body to absorb iron. These water-soluble
vitamins are not stored in the body for long. Good sources should be eaten every day.
In order to live, every cell in the body must be washed in water. Water is needed to carry
other nutrients, to regulate body temperature, and to help get rid of waste wastes. Water is about
60 percent of an adult body weight. Water is found in most foods and in most fruits are more than
90 percent water.
In the early 1990s the basic four food groups, were reworked into the more balanced and
healthy food guide pyramid. The pyramid has at the bottom the grain group; on the second level
are the fruit and vegetable groups; on the third level are the meat and dairy groups; and at the top
is the fats, oils, and sweets group.
Foods from the food guide pyramid can be part of any meal. A grilled cheese sandwich or
a bowl of whole-grain cereal is just as nutritious in the morning as it is at noon. A good breakfast
consists of any foods that supply about one fourth of the necessary nutrients for the day.
The United States government publishes guidelines for appropriate nutrient a person should
get. These are known as the Recommended Dietary Allowances. Just the same as wise shoppers
get the most for their money, so do good consumer buy foods that give the most nutrition for the
lowest number of calories. For example, snacks can provide about one fourth of the calorie
requirements among teenagers. Those snacks provide that much of the day's needs for protein,
minerals, and vitamins. Sandwiches, fruit, and milk make good snacks for teenagers.
Special diets for people with health problems should be prescribed by a doctor. Doctors
usually refer patients to a dietitian, who write up an private diet plan.
The typical diet American diet usually has much more salt than the body needs. People
with high blood pressure have to avoid as much salt as possible. Diabetes is another disease that
needs careful meal planning. When a person has diabetes the body doesn't normally use of blood
sugar. If a person develops diabetes later in life, it usually is controlled with diet alone. Diets
high in fat and cholesterol have been connected with blocking the arteries, a common reason in
heart disease and stroke. Scientist 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.
People who don't eat all animal products are called vegans. These people must plan their diets
carefully to get balanced nutrition.