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Appendix A Nutrients and Their Role in Human Health In additio n t o energy , foo d supplie s a hos t o f chemica l substance s tha t th e body uses for building, repair, and various biochemical reactions necessary for life. Nutrients are divided into energy-producing an d non-energy-producing . The forme r includ e carbohydrates , proteins , an d fats ; th e latte r includ e vitamins and minerals . Energy-Producing Nutrient s Carbohydrates Carbohydrates includ e sugars , starches , an d fiber. Al l plan t food s contai n carbohydrates, a s does milk . Carbohydrates , a s a proportio n o f food intake , range from 50 % to 70%, due mosdy to economic and cultural factors (Szepesi , 1990: 47). Chemically, sugar s ar e simpl e carbohydrates ; starche s ar e comple x carbohydrates. Sugars add flavor and appeal to foods and are generally harmfu l only when eaten in excess, especially in concentrated form. All energy-yielding foods eventuall y metabolize int o simpl e sugars . Starches, or complex carbohydrates, occur along with fiber in vegetables, fruits, grains , an d legumes . Th e nutritiona l rol e o f starche s primaril y i s t o supply a source energy to the bod y (Nationa l Researc h Council , 1989) . Fibers ar e presen t i n man y plants , primaril y i n th e cel l walls . Unles s refining processe s remov e th e fiber, i t i s consumed a s par t o f plan t foods . Water-soluble fibe r lower s blood cholestero l an d glucos e (sugar ) absorption , while water-insoluble fiber speed s up th e transit time of food i n the digestiv e tract and, thus, acts as a natural laxative (Lif e Sciences Research Office, 1987 ; National Research Council , 1989) . 190฀Appendix ฀A฀ Proteins While carbohydrate s provid e energy , protein s literall y provid e muc h o f th e building material for th e huma n body . Chemically, proteins are composed o f about 2 0 amino acids . Of these , 1 1 ar e considere d nonessential—no t becaus e the y ar e unimportant, bu t becaus e th e bod y manufacture s them . Th e nin e essentia l amino acids , o n th e othe r hand , mus t com e fro m foo d (Nationa l Researc h Council, 1989 : 53) . Onc e al l nin e essentia l amin o acid s ar e availabl e i n sufficient quantities , th e bod y manufacture s protein . Al l nin e mus t b e consumed a t th e sam e tim e t o yiel d nutritiona l benefit — a n all-or-nothin g situation. Proteins have many uses in the body. They are used t o make enzymes; to maintain th e balanc e o f fluids an d acid s versu s bases ; t o mak e pigments , antibodies, and hormones; to transport other proteins; and to build such body tissues as bones, teeth, muscles, brain cells, organs, and scar tissue (to promote healing) (Nationa l Research Council , 1989 : 52). The most efficient sourc e of protein i n th e die t i s foods o f anima l origi n becaus e the y contai n al l nin e essential amin o acid s i n th e proportion s tha t th e bod y needs . Thi s i s a n important reaso n fo r th e value tha t mos t people an d culture s place on suc h foods (Abrams , 1987 ; Harris , 1986 ; Lieberman , 1987 ; Simoons , 1994) . A vegetarian diet that provides adequate protein is possible by combining various plant foods (primaril y a grain and a legume) tha t contain different assortment s of amino acids , but i t requires more complicate d calculatio n an d planning . Fats Fats are actually a subset of lipids, which include triglyceride s (fat s and oils) , phospholipids, and sterols. In spite of media attention t o the evils of fat, lipids are importan t t o nutritio n (Alfin-Slate r an d Aftergood , 1968 ; Nationa l Research Council , 1989: 46-7). Their most important role is to provide energ y for bodily functions. Fats provide nine Calories per gram, more than any other nutrient (Nationa l Researc h Council , 1989 : 45). Th e bod...

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