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What is Protein?
What is the structure of protein?
What are some of the issues related to protein
supplements?
What are protein requirements?
What are the possible adverse effects of using
protein supplements?
What are common sources of protein and amino acid products?
What are the effects/actions of l-carnitine?
What are the adverse effects of using l-carnitine
supplements?
Does carbohydrate supplementation during exercise improve
performance? |
Nutritional
Supplements: Protein and Amino Acid
· What
is protein?
Protein is one of the most essential nutrients in our body. It has a wide
range of physiological functions that are required for achieving optimal
physical performance. Protein forms the structural basis of muscle tissue,
is a major source of energy for muscle contraction and is also the major
component of enzymes in the muscle.
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· What
is the structure of protein?
Protein is a complex chemical structure containing carbon, hydrogen and
oxygen similar to carbohydrates and fat. Protein also has nitrogen. These
elements are combined and are formed into amino acids, each possessing
an amino group (NH2) and acid group (COOH), and the reminder being different
combinations of carbon, hydrogen, oxygen and sometimes sulfur. There are
20 amino acid (peptides), all of which can be combined together in different
ways to form proteins that are needed for the structure and functions
of the human body (Williams, 1893).
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· What are some of the issues
related to protein supplements?
1. Athletes may use protein supplements to enhance endurance and increase
or maintain muscle mass to improve strength and size.
2. A high-protein diet doesn't build muscle and burn fat as some people
think.
3. Regular physical activity and dietary protein builds muscle strength.
4. Athletes may need slightly higher levels of protein, derived from protein-rich
foods such as meat, poultry, fish, eggs, and dairy products.
5. Depending on the protein sources chosen, a high protein diet may also
be high in fat and calories.
6. Diets very high in protein can put a strain on the liver and kidneys.
(From The American Dietetic Association's Complete Food & Nutrition
Guide, 1998)
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· What are protein requirements?
1. The RDA for protein is 0.8 grams/kg/day.
2. Adequate energy intake primarily from carbohydrates will insure protein
balance.
3. Urea, a by-product of protein metabolism, increases in the urine during
exercise.
4. Estimates of increased protein requirements for endurance athletes
vary, with recommended protein intakes of 0.97 to 1.39 g/kg/day.
5. Most experts agree that additional protein can be easily obtained through
a balanced diet.
6. Protein need can be calculated as a percentage of total energy and
on a per kilogram body weight basis (American Dietetic Association, 1997).
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· What are the possible adverse
effects of using protein supplements?
1. High protein diets are discouraged by most nutrition experts due to
increased stress placed on the kidneys.
2. The high nitrogen load excreted as urea can cause fluid imbalance leading
to dehydration.
3. Diets high in animal sources of protein are often associated with high
fat intake and increased risk of heart disease.
4. Large ingestion of some amino acids can interfere with the absorption
of other amino acids leading to metabolic imbalances.
5. Mild to severe stomach cramping and diarrhea, dehydration, and gout
have been associated with use of certain amino acid supplements.
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· What are common sources of protein
and amino acid products?
1. The protein content of powdered or liquid protein formulas is derived
form natural food sources such as milk, egg, or soy protein.
2. Amino acids marketed as ergogenic aids include the branched chain amino
acids (BCAA) leucine, isoleucine, and valine. During exercise the liver
releases BCAA which are delivered to the muscle. Degradation of muscle
protein which also occurs during exercise leads to the production of BCAA
within the muscle.
3. Leucine is the only amino acid that can be oxidized for energy and
is important in muscle metabolism because it can provide energy to muscle
during starvation. Leucine also has a stimulatory effect on the secretion
of insulin.
4. Over secretion of insulin can result in a decrease blood sugar and
reduced athletic performance.
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· What are the effects/actions
of l-carnitine?
Carnitine (L-3
hydroxytrimethylammoniobutanoate) has several roles on the mammalian cellular
metabolism. L-carnitine is believed to increase long chain fatty acid
oxidation in skeletal muscle during exercise. Dietary sources of carnitine
are meat and diary products. Advocates of L-carnitine supplementation
claim that it increases aerobic and anaerobic capacity and promotes fat
loss. The most commonly cited dosage of oral carnitine is 2-6 g/day consumed
in two to three doses with meals. L-carnitine supplementation may have
beneficial properties, however, there is a lack of information regarding
its long term use (Tonda and Hart, 1992).
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· What are the adverse effects
of using l-carnitine supplements?
Nausea, vomiting, abdominal cramps, diarrhea
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· Does carbohydrate supplementation
during exercise improve performance?
Research has shown that carbohydrate supplementation during exercise can
improve long-term endurance performance (for activities lasting 90 minutes
or more) and delay fatigue 30 to 60 minutes. The most recent guidelines
on carbohydrate supplementation during exercise are the following recommendations:
1. Consume 200-400 ml of a moderately concentrated 5-7% carbohydrate drink.
2. Continue consuming 100-150 ml of the same drink at 10-15 min intervals
for the first two hours of exercise.
3. After two hours switch to a more concentrated drink (15-20% carbohydrate).
4. Choose a drink that is palatable.
5. One alternative to purchasing sports drinks is to dilute any fruit
juice 1:1 with water and add a teaspoon of salt per liter. This should
approximate carbohydrate, electrolyte and osmolality values of commercial
sports drinks (Wolinsky, 1997).
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Information from NCAA, http://www.drugfreesport.com/choices/supplements/index.html
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