HE-748 SPORTS NUTRITION FOR YOUNG ADULTS #1 PROTEIN
HE-748, New May 1997. Robert E. Keith, Professor, Nutrition and Food Science, Auburn University
| Sports Nutrition For Young Adults #1
Protein |
All people, whether they are physically active or not,
have a dietary requirement for a certain amount of protein. Actually, the
requirement is not for protein but for the amino acids or building blocks
of protein.
Protein And Exercise
Proteins perform several important and necessary functions in the body
when a person exercises.
- Protein makes up approximately 20 percent of all muscle tissue.
- All the enzymes in the body are proteins. Enzymes are compounds that
drive chemical reactions. For example, the chemicals that help produce
energy from carbohydrates and fats are enzymes.
- Proteins in blood help control the body's water balance. Proteins also
help transport nutrients to cells and waste products away from cells.
- Antibodies that function in the immune system are proteins.
- Protein also can be used as a source of energy (calories) for the body
although carbohydrates and fats are the body's major sources of energy.
What Are Proteins?
Proteins are made up of approximately twenty-two amino acids. These amino
acids differ in the way they are organized and in the total number of amino
acids in the protein. In other words, if proteins are like words, then amino
acids are like the letters of the alphabet that make up those words.
Amino acids can be grouped into those needed in the diet (essential amino
acids) and those that can be found in the diet but also can be made in the
body (nonessential amino acids). All proteins contain some essential and
some nonessential amino acids. The more essential amino acids a protein
contains, the better the quality of the protein.
Average Dietary Requirements For Protein
Dietary protein requirements have been established for lightly active
people. This minimum protein requirement is set at about 0.25 grams of protein
for each pound of body weight. However, because many people don't eat what
they should, the Recommended Dietary Allowance (RDA) for protein has been
set somewhat higher than the minimum requirement. Thus, the RDA for protein
is approximately 0.4 grams per pound of body weight.
In an average American diet, protein supplies approximately 15 percent
of the calories. This amounts to 75 to 120 grams of protein a day in the
typical person's diet. This amount is well above the RDA for protein for
most people.
Athletes' Dietary Requirements For Protein
Researchers have studied the protein needs of athletes for several years.
Most of these studies did find that athletes of all types (aerobic and strength)
have somewhat greater protein needs as compared with the average person.
The protein needs of athletes in these various studies have ranged from
0.5 to 1.2 grams of protein per pound of body weight per day. These values
are just above the RDA to about three times the RDA. The usual protein recommendation
for athletes is now established at 0.7 grams per pound of body weight per
day. The protein needs of various athletic groups can be seen in Table 1.
Table 1. Protein Requirements Of Various
Athletic Groups.
| Athletic Group |
Protein Requirement* (grams/pound of body weight) |
| Elite weight lifters |
0.6 to 1.3 |
| Strength athletes |
0.6 to 0.9 |
| Endurance athletes |
0.5 to 0.7 |
| Endurance runners |
0.7 |
| Elite bodybuilders |
0.5 |
| Note: The protein requirements vary because this information
is based on separate studies from different researchers. |
The protein needs of aerobic athletes (runners, soccer players, etc.)
increase because part of the energy used to perform aerobic work comes from
protein. Aerobic athletes burn a lot of energy so this increases their protein
requirement. The protein needs of strength and power athletes (weight lifters)
are frequently greater because of the increase in muscle mass associated
with athletes in these sports.
Influence Of Other Factors On Athletes' Protein Requirements
While protein needs of athletes may be greater, these needs can increase
or decrease depending on several factors. Four of these factors that can
greatly influence protein requirements are (1) the total number of calories
the athlete consumes, (2) the total carbohydrate intake of the athlete,
(3) the quality of the protein consumed, and (4) the overall training stress
on the athlete.
Athletes need more protein than the
average person. |
Male
(160 pounds) |
Female
(125 pounds) |
| Normal Activity |
Athletic Activity |
Normal Activity |
Athletic Activity |
64 grams
protein/day
(0.4 x 160) |
112 grams
protein/day
(0.7 x 160) |
50 grams
protein/day
(0.4 x 125) |
87.5 grams
protein/day
(0.7 x 125) |
Calorie Intake. One of the top priorities of the body is to provide
sufficient calories to essential body tissues. If calorie needs are not
being met, the body will use protein for calorie needs. This will, in turn,
increase the protein requirement of the person. Thus, a low calorie intake
will increase an athlete's protein requirement while a high-calorie diet
will decrease protein needs.
Carbohydrate Intake. Adequate intake of carbohydrates fuels muscle
and brain tissue, sparing the use of protein as a fuel source for muscle
and brain tissue. Thus, high-carbohydrate diets often recommended to athletes
will reduce the protein requirement of that athlete.
Protein Quality. Some proteins are better at being used for muscle-
and tissue-building purposes than other proteins. These proteins are known
as high-quality proteins because they contain a lot of the essential amino
acids and are easily digestible. Lower quality proteins contain fewer essential
amino acids and frequently are less digestible. The consumption of high-quality
protein will reduce an athlete's protein requirement. A list of higher quality
and lower quality protein sources can be seen in Table 2.
Table 2. Protein Quality Of Some Selected
Foods.
| High-Quality Protein |
Lower-Quality Protein |
| Eggs |
Corn |
| Milk |
Wheat |
| Meat, fish, poultry |
Nuts |
| Soy proteins |
Beans, peas |
Training Stress. As an athlete moves to a higher level of training
(increased volume or intensity) protein requirements will increase temporarily
until the athlete adapts to the new level of training. Thus, protein requirements
increase with increased training stress.
Protein In The Diets Of Athletes
While protein requirements may be higher for athletes and other physically
active persons, most of the time a normal diet will more than cover the
increased need for protein. Several studies have shown that many athletes
often consume 0.7 to 1.4 grams of protein per pound of body weight each
day. Many athletes eat more than 200 grams of protein each day. These amounts
are well above the increased daily requirement of protein for most athletes.
Many foods consumed by athletes contain ample amounts of protein. Some
of these foods with their protein content are shown in Table 3. An athlete
who consumes 4 ounces of chicken, 3 cups of skim milk, 1 cup of peas, 4
slices of bread, and 2 cups of spaghetti would be getting 100 to 105 grams
of protein. Many athletes eat much more than this in a day.
Table 3. Protein Content Of Some Selected
Foods.
| Food |
Serving Size |
Protein Content (grams) |
| Beef |
3 ounces |
20 to 25 |
| Pork |
3 ounces |
18 to 21 |
| Chicken |
3 ounces |
18 to 24 |
| Fish |
3 ounces |
17 to 24 |
| Beans, peas |
1 cup |
14 to 16 |
| Nuts |
1/2 cup |
12 to 18 |
| Grains (rice, etc.) |
1 cup |
11 to 16 |
| Milk |
1 cup |
8 to 9 |
| Eggs |
1 large |
6 to 7 |
| Cheese |
1 ounce |
5 to 7 |
| Bread |
1 slice |
2 to 3 |
What About Protein Supplements?
An athlete would probably need to monitor protein intake only during
times of calorie restriction. While protein supplements would not normally
be needed, inexpensive high-quality sources such as powdered milk and cooked
egg whites could be obtained from grocery stores. This would eliminate the
need to take expensive supplements offered by many companies.
For More Information
Benardot, D. Sports Nutrition: A Guide For the Professional Working
with Active People. The American Dietetic Association, Chicago, IL.
1993.
Berning, J. R., and S. N. Steen. Sports Nutrition for the 90s.
Aspen Publishers, Inc., Gaithersburg, MD. 1991.
Clark, N. Sports Nutrition Guidebook. Leisure Press, Human Kinetics
Publishers, Inc., Champaign, IL. 1990.
For more information, contact your county Extension office. Look
in your telephone directory under your county's name to find the number.
Issued in furtherance of Cooperative Extension
work in agriculture and home economics, Acts of May 8 and June 30, 1914,
and other related acts, in cooperation with the U.S. Department of Agriculture.
The Alabama Cooperative Extension System (Alabama A&M University and
Auburn University) offers educational programs, materials, and equal opportunity
employment to all people without regard to race, color, national origin,
religion, sex, age, veteran status, or disability.
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Issued in furtherance of Cooperative Extension work in agriculture and
home economics, Acts of May 8 and June 30, 1914, and other related
acts, in cooperation with the U.S. Department of Agriculture. The Alabama
Cooperative Extension System (Alabama A&M University and Auburn
University) offers educational programs, materials, and equal
opportunity employment to all people without regard to race, color,
national origin, religion, sex, age, veteran status, or disability.
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