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L-1232
PROTEIN
Mary K. Sweeten*
The word "protein" comes from a Greek word thatitprovides. Thebodycanmakesomeoftheamino
meaning"primary" or "tocome first." Early chemists acids it needs, but other amino acids must come
gave protein this name because theyfelt that proteins "ready-made"infoods. Theaminoacids thatthebody
were the most important of all substances in the or- must have "ready-made" are called essential amino
ganic kingdom. All living things, both plant and ani- acids. There are eight ofthese essential amino acids.
mal, contain protein. Today we know that protein is A protein that provides all of the eight essential
one ofsix key nutrients necessary for good health in aminoacidsiscalledacompleteprotein. Aproteinthat
humans. Proteins, minerals, vitamins, carbohydrates, lacks one or more ofthe essential amino acids is called
fats and water make up these six key nutrients. an incomplete protein. The body needs some ofboth
Function kinds ofproteins. Some foods provide complete pro-
tein while others provide incomplete protein.
Themainfunction ofproteininthebodyis tobuild Most proteins that come from animal sources
and repair tis ues. The nutrient protein is needed by (meat, poultry, fish, eggs, cheese and milk) are com-
everycellin thebody. As achildgrows, hismusclesare plete proteins, while most plant proteins are incom-
builtfrom proteins. Adults also need protein to repair plete. Theplantproteins, whichareimportantsources
theirmuscles as well as othertissues. Proteins are also ofincomplete proteins, can be combined with animal
important in enzymes, which start chemical reactions foods to provide all the essential amino acids.
so thebodycanusethefood you eat. Proteincanactas
a regulating substance. Finally, protein canbeusedto Protein Requirement
provide energy. When carbohydrates, sugars and Everyone needs some protein each day, but the
starches, andfats areavailable, however, the bodywill amount needed daily depends on body size, rate of
usetheseforenergyandallowproteintobeusedforits growth, and individual repair and maintenance re-
other functions. quirements. The NationalResearch Councilhas setup
Protein Structure recommendedamountsofproteinfor eachsexandage
group. The accompanying chart lists the recom-
Proteinis oneofthe mostabundantcomponentsin mendedamountofproteinfor each sex andage group
the body. Most ofthe body's protein is located in the as well as recommended amounts for consumption
muscle tissue. Different kinds ofprotein occur in the during pregnancy and lactation periods.
blood, soft tissues and teeth. Sources of Proteins
Forexample, proteinsaremadeupofsmallerparts
called amino acids. These acids act as building blocks. Most foods contain some protein, but some are
Theyjointogethertomakeaprotein. Theremaybeas better sources of protein than others. Animal foods,
manyas 280oras few as 2 amino acids that make up a such as meat, fish, poultry, eggs, cheese and milk,
protein, butmostproteinsinfoods andin thebodyare which have complete proteins, are the best food
made up of12 to 22 amino acids. sources ofproteins. Drypeas, beans, nuts andpeanut
Nutritive Value Of Proteins butter which contain almost-complete proteins are
also good sources. Cereal and pasta products, impor-
Since proteins are made up of amino acids, the tant sources ofincomplete proteins, can be combined
nutritivevalueofaproteindependsontheaminoacids with animalfoods to give all the essential amino acids.
Eatingavarietyoffoodsthatfurnish proteinsis impor-
tant to good nutrition.
*Exten ion foods and nuhition specialist, TheTexas A&M Univer- Recently a number of textured soybean products
sity ystem. have appeared on the market. Sophisticated methods
14.13
Texas Agricultural Extension Service. The Texas A&M University System. Daniel C. Pfannstiel, Director. College Station
Recommended Daily Dietary Include a protein-rich food at each meal. Milk
group foods and bread and cereal group foods eaten
Allowances for Protein duringthe dayalso will add protein even though they
are not meat group foods.
Ages Protein Studies indicate that consumers spend from 30 to
Class (Years) (Grams) 40percentofthefood dollaron meatgroupfoods. By
usingless expensive cuts ofmeator substitutingmeat
Children 1- 3 23 alternates like eggs, dry beans and peas, nuts and
4- 6 30 peanutbutter, theconsumercanassureadequatepro-
7-10 36 tein at a lower cost. Less expensive cuts ofmeat pro-
vide as much protein as higher cuts ofmeat, but they
Males 11-14 44 are usually less tender. Combining high-quality ani-
15-18 54 mal proteins with incomplete vegetable protein or
19-22 52 textured vegetable protein products is anotherway to
23-50 56 insure good nutrition and still economize on the food
51+ 56 bill.
Females 11-14 44 Usealowtemperatureandcookprotein-richfoods
15-18 48 longer. High temperatures toughen the protein and
19-22 46 result in an undesirable product. Use moist heat
23-50 46 method ofcooking such as stewing, braising or pres-
51+ 46 sure cooking when cooking less tender, inexpensive
Pregnancy Amountfor age + 30 cutsofmeatorfowl. Thisis themethodrecommended
for less tendermeatbecausemoistheathasa tenderiz-
Lactation Amount for age + 20 ing effect.
Most protein-rich foods require refrigeration to
prevent spoilage. Nuts, dry beans and peas, peanut
butter and some cheeses can be stored safely at room
of extraction, handling and fortifying soy products temperatures.
help them comeclose to meatin the kind and amount Eat a well-balanced diet that promotes health to
ofaminoacids present. Meatanalogs - texturedveg- insure protein and other nutrients in the correct
etableproteinproducts- madetolook, cookandtaste amounts each day.
like meat, have a low saturated fat contentand almost
no cholesterol. If these products are fortified with
vitamins and minerals they can be close to meat in References
nutritive value. Although textured vegetable protein Recommended Daily Dietary Allowances. Washing-
productsareversatile, abetteraminoacidbalancemay ton, D. C.: Foods and Nutrition Board, ational
beobtainedbyaddingaminoacidsfrom othersources, AcademyofSciences- ational Research Coun-
such as vegetable proteins, or meat or other animal cil, 1973.
materials to texture vegetable protein products.
Meal Planning Robinson, Corinne H., Proudfit-Robinson's Normal
In ure that you get all the protein you need each and Therapeutic Nutrition. Thirteenth Edition.
day by following the Daily Food Guide for the four NewYork: The Macmillan Company, 1967.
basic food groups.
The Daily Food Guide recommends that you eat "SoybeansinFamily Meals," USDABulletin H & GB
two ervings ofmeatgroupfoods each day. A serving 208.
from the meat group is three ounces of lean cooked
meat, fish or poultry. One-halfserving ofmeat group Wilson, Eva D.; Katherine H. Fisher; and Mary E.
foods is 1 egg, % cup of dried peas or beans or 2 Fugua. Principles of Nutrition. Second Edition.
tablespoons ofpeanut butter. NewYork: John Wiley and Sons, Inc., 1967.
Educational proarams conductedby the Texas AgriculturalExtension Service serve people ofall ages regardless ofsocio-economic levels, race,
color, sex, religion or national origin.
Cooperative Exten ion Work in griculture and Home Economics, TheTexas A&M University System and the United State Departmentof
gJiculture coop rating. Distributed in furtherance of the Acts ofCongress of May 8, 1914, as amended, and June 30, 1914.
30M - 3-76, Revis d F&
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