The Facts About Nutrition
Nutrition may be defined as a science that deals with the food materials that the living organism takes in and the processes through which these materials maintain life and sustain all the activities of the organism. It is a science that deals with the control of health insofar as it is affected by food.
A balanced diet, rich in vitamins, minerals and other nutrients can prevent deficiency diseases as well as maintaining good health.
Foods and their functions in nutrition in relation to health may be considered under four categories: (1) food as a source of energy, (2) food as a source of protein, (3) food as a source of mineral elements, and (4) food as a source of vitamins.
Like any machine, the human body must have fuel to carry on its work. There are three kinds of fuel it is capable of burning: proteins, fats, and carbohydrates. Most foods contain all three fuels, but some of them contain only one; for example, sugar furnishes only carbohydrates, lard furnishes only fat, and gelatin furnishes only protein. Each of these fuels, however, furnishes food energy.
Foods that are high in fats furnish more calories per gram than foods that are high in either carbohydrates or proteins. In a healthy human being living on an ordinary mixed diet the fuel value for protein is 4 calories per gram, for fat 9 calories per gram, and for carbohydrate 4 calories per gram.
All foods furnish calories, but in different amounts depending on their composition. To carry on normal daily activities, one's food supply must furnish enough calories to meet the energy requirement if he is to maintain his weight. When the total food eaten furnishes more calories than are needed to meet the energy expenditure, increase in weight occurs because the surplus calories from the food eaten are stored as fat in the body.
Weight loss occurs when the food intake furnishes fewer calories than are needed to meet the energy expenditure, and the stored body fat is used to make up the deficit.
The term metabolism (or combustion) refers to all of the chemical changes that take place in food after it has been absorbed from the alimentary tract. The total energy metabolism includes (1) the energy expenditure for the internal work of the body, or basal metabolism, (2) the energy expenditure for activities, and (3) the energy required for the burning of the food in the body. In addition to these three energy quotas children need energy for growth.
The internal work of the body includes that of the lungs in breathing, the heart in pumping blood through the blood vessels, and the muscles in maintaining muscle tone. In addition, each of the body's more than 100 trillion cells requires energy in order to carry on all of its biochemical processes.
Protein is the chief constituent of all cells, whether animal or vegetable. So our bodies consist largely of protein. It forms a structure around which calcium and phosphorus deposit to make bones. Hair and nails are made of protein. Collagen, the 'glue' between our cells, holding us together, is a protein. Our tendons, muscles and organs are made up of protein. Even our hormones, enzymes and blood contain protein.
A regular intake of protein in the diet provides your body cells with an adequate supply of amino acids. Cells then use these chemical units as building blocks to form new proteins.
Protein, a term derived from a Greek verb meaning "to take first place", was first described by the Dutch chemist Gerardus Johannes Mulder in 1838, as a material found in plant and animal tissues which contained nitrogen in addition to carbon, hydrogen, and oxygen. The fact that this material contained nitrogen characterized it as being different from the other two fuels in foods, namely, carbohydrates and fats, which contain only carbon, hydrogen, and oxygen. Proteins are essential constituents of body fluids with the exception of the bile and the urine. They are essential to all forms of plant and animal life. Unlike plants, which build their protein from inorganic materials from the soil and air, animals cannot build proteins this way. Animals must obtain either proteins or amino acids from foods to form body tissue.
Foods that furnish proteins which will maintain life and provide for normal growth of the young when used as the only source of a protein food in the diet are said to furnish "complete" proteins. Milk, cheese, eggs, fish, meat, and poultry are examples of foods furnishing "complete" proteins.
Protein is essential for maintenance of body tissues, growth of new tissue, formation of hemoglobin in blood, the building of antibodies to protect against certain infections, maintenance of normal osmotic pressure in the body fluids, the formation of hormones and enzymes that help in oxidation-reduction reactions in the body as well as for enzymes assisting in the process of digestion.
Proteins in foods are broken down in the process of digestion to amino acids, which are absorbed through the intestinal wall. The amino acids circulate in the bloodstream, making it possible for each body protein to be built up from the assortment of amino acids that it needs. The surplus amino acids have to be broken down to glucose (a carbohydrate) and urea (a nitrogen product that is excreted in the urine). Because of the extra work imposed on the kidneys in the breaking down of surplus amino acids and the fact that protein is not stored to any extent in the body, protein is an expensive fuel.
Minerals are known to play a role in controlling the metabolism or maintaining the fucntion of specific body tissues. Among the 21 mineral elements that have been found in the human body are at least 14 that are now recognized as doubtless essential. These include calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium, iron, manganese, copper, iodine, cobalt, fluorine, and zinc.
The remaining elements, which have been found in either very minute quantities or traces, include silicon, boron, arsenic, strontium, aluminum, bromine, and nickel.
Fortunately, nature provides those mineral elements needed in smaller amounts in a variety of foods and if one makes certain that the foods in his diet provide calcium, iron, and iodine the chances are quite good that other mineral elements will be found in sufficient amounts for the maintenance of health, assuming, of course, that essential nutrients other than the mineral elements are satisfactorily provided.
For more information on Minerals see my hub titled Minerals FAQ.
Vitamins are vital. Your health will suffer if you do not take in your RDA of every single vitamin. Most of these vitamins must be obtained from your diet. A balanced, mixed diet will naturally contain all the vitamins needed by the body and therefore supplements are needed only by those people who are in poor health, suffer form chronic illness, or do not eat well.
The term "vitamin" is now used to refer to any one of a group of substances that occur naturally in foods in minute quantities and that produce specific physiological effects and are essential to the normal development and maintenance of health. Vitamins are usually classified as either fat-soluble or water-soluble. The fat-soluble vitamins include vitamins A, D, K, and E. The water-soluble vitamins include ascorbic acid (vitamin C) and a large group of vitamins now known as the B-complex vitamins. The most important members of the B-complex vitamins include thiamine (vitamin B1), riboflavin (vitamin B2), nicotinic acid (niacin or B3), pyridoxine (vitamin B6), pantothenic acid, folic acid, vitamin B12, biotin, choline, and inositol.
For more information on Vitamins see my hub titled Vitamins FAQ.
Some factors to be considered when working out a person's nutritional needs: age, weight, height, sex, occupation, sleep patterns, marital status, emotional environment, heredity illnesses, bowel and urinary patterns, personality and attitudes, appetite, food cravings and hates, energy levels, any medications, other body functions.
Recommended Daily Dietary Allowances
Scientists have identified a range of nutrients that must be present in the diet. The amounts that should be taken each day are called Recommended Dietry Intakes. These figures are only an average. If everyone took in the recommended amount of nutrients, most people would be well-nourished.
The recommended allowances can be obtained from a good selection of available foods, and these common foods will also provide other mineral elements and vitamins for which requirements are less well known. Thus diets that provide the recommended allowances should provide all those nutrients that are known to be of importance in promoting optimum health and efficiency. Surplus intakes of most of the nutrients other than calories can be considered favorably, but a continued surplus of calories will lead to overweight and this should be guarded against.
Also, although these figures are given per day, you need not eat every nutrient, every day - you can achieve your intake of nutrients over a seven-day period.
A Simple Refueling Operation
Your body is a machine just like a car - with a few added extras. If you put in top grade fuel and oil into the family car with a regular tune-up it runs smoothly and efficiently and so will your body witha balanced diet, a little exercise to keep the motor running well and adequate rest and relaxation.
Today, people can maintain higher levels of health, vigor, and efficiency throughout many more years than would have been possible even 50 years ago. Better nutrition has not only added years to our lives, but life to our years.
The Whole Health Manual, Patrick Holford, Lothian Publishing Company, 1983. Page 59.
The Complete Guide to Family Health and Fitness for Australians, Dr Stephen Carroll, Simon & Schuster, 1992. Page 306.
Newnes Family Health Encyclopaedia, G Somerville (ed.), London, George Newnes, 1959. Page 495.
Nutrition Book, Jeni Edgley, Lansdowne Press, 1985. Page 17.