broken down and released as glucose at the exact rateneeded by the body. This latter mechanism iscontrolled largely by insulin from the pancreas.During fasting, liver glycogen is rapidly depleted,leading the body to use its fat for energy. Carbo-hydrates that are not needed for energy are converted toand stored as adipose (fat) tissue.The main functions of carbohydrates are tofurnish the main source of energy formuscular work and nutritive processes,help maintain body temperature,form reserve fuel,assist in oxidation of fats, andspare protein for growth and repair.MINERALSAlthough mineral elements constitute only a smallportion of the total body weight, they enter into theactivities of the body to a much greater degree thantheir weight would indicate. Certain mineral elementsare essential for specific body functions. While it is notyet known exactly how many of the mineral elementsare indispensable to the body functions, seeminglysmall changes of mineral concentration can be fatal.These essential inorganic elements contributeoverwhelmingly to the skeletal framework of the bodyand teeth, and they are an essential part of manyorganic compounds.Minerals form an integral part of basic cellstructure and circulate in body fluids. They alsoexercise specific physiologic influences on thefunction of body tissues. For mineral needs to be metsatisfactorily, consumption of each element must besufficient to cover body tissue requirements and tomeet changing physiological needs. At one time, itwas erroneously believed that any diet adequate inother respects would also provide an adequate intakeof essential minerals. This is not so. Foods varygreatly in their mineral—as well as their overallnutritional—content, depending on growingconditions, storage, and preparation procedures.Among the major minerals are calcium, phosphorus,iron, potassium, zinc, and magnesium. Table 9–1 liststhe essential elements, the foods that contain them, andtheir functions.VITAMINSVitamins are essential compounds that are presentin food in minute quantities. Although vitamins do notfurnish energy or act as tissue-building materials, theydo act as catalysts in many body chemical reactionsand are necessary for normal metabolic functions,growth, and the health of the human body. Theirabsence results in malnutrition and specific deficiencydiseases. Vitamin chemistry is complex andnutritional experimentation is difficult, so ourknowledge of them is being continually supplementedand revised. It is quite possible that additionalvitamins will be discovered or that some of thosealready recognized may prove to contain more thanone factor.Vitamins are so widely distributed in food that aproperly prepared normal diet usually provides anadequate amount. Vitamins can be destroyed duringthe preparation or preservation of certain foods;however, manufacturers frequently add vitamins totheir products to replace those destroyed or removed inprocessing. Since fat-soluble vitamins can be stored inthe body, it is possible to develop hypervitaminosis byconsuming excessive amounts of these nutrients, anddeath may result in extreme cases. Fat-solublevitamins include A, D, E, and K.Vitamin A is involved in the formation andmaintenance of healthy skin, hair, and mucousmembranes. Vitamin A helps us to see in dimlight and is necessary for proper bone growth,tooth development, and reproduction. Goodsources of vitamin A include yellow, orange, anddark green vegetables; fruits; and liver, eggs,cheese, butter, and milk.Vitamin D promotes calcium and phosphorusabsorption and is required for the formation ofhealthy bones and teeth. Good sources includefortified milk, egg yolk, liver, tuna, and cod liveroil. Vitamin D is produced in the body onexposure to sunlight.Vitamin E protects vitamin A and essential fattyacids from oxidation in the body cells andprevents breakdown of body tissues. Goodsources include vegetable oils, fortified cereals,whole-grain cereals and bread, nuts, wheatgerm, and green leafy vegetables.Vitamin K includes a group of vitamins thatpromote normal clotting of the blood and helpsmaintain normal liver functions. Good sources9-3
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business