Oklahoma Cooperative Extension Service T-3163

Protein and the Body

October 2019

Janice R. Hermann, Ph.D., RD/LD

Nutrition Specialist Oklahoma Cooperative Extension Fact Sheets
are also available on our website at:
facts.okstate.edu
Protein Is a Nutrient
Protein is a nutrient that the body needs to grow and
maintain itself. Next to water, protein is the most plentiful to our protein intake. However, each type of plant protein is
substance in our bodies. Just about everyone knows that low in one or more of the essential amino acids. This makes
muscles are made of protein. Actually, every single cell in the them a lower quality protein. Animal proteins contain a better
body has some protein. In addition, other important parts of balance of the essential amino acids than plant proteins.
the body like hair, skin, eyes, and body organs are all made People who do not eat animal products should eat dif-
from protein. ferent types of plant foods together or within the same day to
Many substances that control body functions, such as get the proper balance and amount of essential amino acids
enzymes and hormones, also are made from protein. Other their bodies need. Combining beans and rice, or beans and
important functions of protein include forming blood cells and corn, or peanut butter and bread will provide all of the essential
making antibodies to protect us from illness and infections. amino acids in the right amounts. These food combinations
mix foods from different plant groups to complement the amino
Amino Acids acids provided by each.
Combining foods from any two of the following plant
Proteins are made from simpler substances called amino groups will make a higher quality protein:
acids. There are 20 amino acids in the protein that we eat • Legumes, such as dry beans, peas, peanuts, lentils,
every day. The body takes these amino acids and links them and soybeans
together in very long strings. This is how the body makes all • Grains, such as wheat, rye, rice, corn, oats, and barley
of the different proteins it needs to function properly. Nine of • Seeds and nuts, such as sunflower and pumpkin seeds,
the amino acids are called essential because bodies cannot pecans, and walnuts
make them. These essential amino acids must come from the
foods we eat. Combining a small amount of animal protein with a larger
Figure 1 shows a diagram of the hormone insulin that amount of plant product can also meet a person's protein
regulates blood glucose (sugar). Insulin is a very small protein. needs. Thus, combining a small amount of any of the follow-
Many proteins are made of thousands of amino acids strung ing animal products with any of the plant groups listed above
together. The letters in the circles are the abbreviations for will make a higher a higher quality protein.
the amino acid that is in that location. Proteins can be very • Eggs
complex because of all the combinations of amino acids that • Dairy products, such as milk, cheese, and yogurt
make up the chains. • Meat, such as beef, poultry, fish, lamb, and pork

Foods that Contain Protein Other Uses for Protein
Both plant and animal foods contain protein. Foods that Three major nutrients provide calories: protein, carbohy-
provide all the essential amino acids are called high quality drate, and fat. Each gram of protein and carbohydrate provides
proteins. Animal foods, like meat, fish, poultry, eggs, and dairy
products, are all high quality protein sources. These are the
foods people usually think of when they want to eat protein.
The essential amino acids in animal products are in the right
balance.
Foods that do not provide a good balance of all the es-
sential amino acids are called lower quality proteins. Plant
foods contain lower quality proteins. Most fruits and vegetable
are poor sources of protein. Other plant foods, like baked
beans, split peas and lentils, peanuts and other nuts, seeds,
and grains like wheat, are better sources. They contribute a lot
Figure 1. Amino acids in the protein insulin.

Division of Agricultural Sciences and Natural Resources • Oklahoma State University

4 calories. The best use for protein is to repair and maintain It is important to keep in mind that extra protein does not
body tissues. If people eat more protein than they need for give special benefits. People do not store extra dietary protein
tissue maintenance and repair, their bodies use it for energy. as body muscle. Extra protein beyond what the body needs will
If it is not needed for energy, their bodies use extra protein not make extra muscle or grow hair faster or protect against
to make fat. It then becomes part of fat cells. If people do not diseases. Protein beyond what is needed is either broken
eat enough calories, protein in food and in their bodies will down and used for energy, or it is turned into fat and stored
be used for energy. If this happens, protein is not used for its in fat cells. Too little protein will result in a gradual breakdown
main purpose, which is to maintain the body. Getting enough of body protein tissues and loss of muscle tissue. The body
protein and eating a balanced diet with adequate calories are will not be able to function properly under these conditions.
important. This way, protein will be used for tissues and other The best way to meet protein needs is to eat the recom-
protein functions. Fat and carbohydrate will be used to meet mended amount of food from each of the USDA MyPlate food
energy needs. groups. Recommended amounts from each USDA MyPlate
food group each day for a reference 2,000 calorie diet are:
Protein Requirements • 6 oz. of grains
Every person needs to eat protein. How much protein he • 21/2 cups of vegetables
or she needs depends on his or her body size and special • 2 cups of fruit
needs, like growth. Children need more protein per pound of • 3 cups of dairy
body weight than adults because they are growing and build- • 5 1/2 oz. of protein foods
ing new protein tissue. Pregnant and nursing women need • 6 teaspoons of oil
more protein for growth of the baby and to produce milk. The
Dietary Reference Intake (DRI) tell us the amount of protein Table 1 shows the protein and fat content of various com-
an average person needs each day. Calculate the protein mon foods.
needs based on the formula of 0.8 grams of protein for each To get the protein needed without too much fat or saturated
kilogram of body weight. To find weight in kilograms, divide fat, choose lean cuts of meat and lean fish, and remove the
weight in pounds by 2.2. skin from poultry. Cooked legumes and grains are low in fat if
you do not add fat when cooking and are inexpensive sources
of protein. Nuts and peanut butter are good sources of protein
Example: but are also high in fat. Eggs are also an inexpensive source
of protein. Choose low fat dairy products often, and do not
Person’s weight = 165 pounds add fat when cooking or serving these foods.
By watching protein sources and eating a diet following
165 pounds/2.2 pounds the USDA MyPlate Plan, people can be sure that they are
per kilogram getting enough protein to meet their requirements without
getting extra fat that they don’t need.
75 kilograms X 0.8 grams
per kilogram
References
This person has a protein requirement of 60 grams per Whitney, E.N. & Rolfes, S.R. (2015). Understanding Nutrition,
day. 14th ed., Wadsworth, Cengage Learning, Belmont, CA.
Another simple, shorthand approach is to multiply body United States Department of Agriculture. ChooseMyPlate.gov.
weight in pounds by 0.4. This is a rough estimate involving Accessed at www.choosemyplate.gov
fewer calculations.

Example:
165 pounds X 0.4 = 66 grams per day.

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Table 1. Protein in Common Foods, Grams per Serving

Food and serving size Protein (g) Fat (g)

Chicken, light meat, no skin 3 ounces, cooked 26.3 3.0

Pork roast, 3 ounces, cooked 23.9 8.9
Chicken, dark meat, 3 ounces, cooked 23.3 9.3
Beef, round steak, 3 ounces, cooked 22.6 4.9

Cheddar cheese, 3 ounces 21.1 28.2

Cottage cheese, low fat, 1/2 cup 15.6 2.2
Milk, skim, 1 cup 8.4 0.4
Egg, 1 whole 6.3 5.3

Peanut butter, 2 tablespoons 7.9 16.0

Baked beans, 1/2 cup 6.6 1.3
Sunflower seeds, 1/4 cup 6.2 15.9
Pecans, 1/4 cup 2.3 20.2

Oatmeal, 3/4 cup 4.6 1.8

Rice, 1/2 cup 2.8 0.3
Whole wheat bread, 1 slice 2.6 1.5
White bread, 1 slice 2.5 0.9

Apple, 1 whole 0.3 0.5

Green beans, 1/2 cup 0.9 0.1
Broccoli, 1/2 cup 2.3 0.1

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