ISSA SN Chapter 4: Protein and Amino Acids: Muscle Builders and More
ISSA SN Chapter 4: Protein and Amino Acids: Muscle Builders and More

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    Chapter Goals:

    • Describe and define the main terms relating to amino acids and protein.
    • Know the different types of amino acids and protein and their major functions.
    • Find the nonessential and the essential amino acids.
    • Know how the proteins and amino acids affect the athletic performance and their health. 


    Proteins and their building blocks, amino acids will be discussed in great detail throughout this chapter. Protein is a vital part of the diet and it has so many roles within the body. the roles are mostly structural, but the protein may also be used for the body as energy during intensive exercise for meeting the metabolic needs when the nutrition is not adequate enough. When this happens, the body breaks down the muscle tissue to use its proteins. This is a big setback for athletes training to make gains in muscle. 

    If we take in too much protein in the diet, we will store this as fat, just as we normally do with the excess carbs. This allows for increases in the ammonia and the uric acid. They are both waste products. 

    Athletes aim to keep their protein intake at the right level based on their body weight, their level of activity, and the composition of the muscle fibers. The endurance athletes will usually need more protein due to the higher amount of slow twitch fibers, but this is only when compared to the general population. The strength athletes have larger muscles and more fast twitch fibers, meaning they need the greatest amount of fibers. 

    What is Protein?

    Protein is one of our macronutrients, and perhaps the most important of them. It is a polypeptide which is a compound that has 10 – 100 amino acids making it up. The amino acids are held together with a peptide bond, which is a form of a special chemical bond. 

    Significance of proteins and amino acids for athletes:

    • Protein is the source of the amino acids.
    • Athletes are going to need a higher intake of these proteins compared to the general population.
    • Amino acids are known as the building blocks for recovery, growth, and production for many bodily proteins.
    • Branched chain amino acids are special amino acids used for energy and needed in greater amounts.
    • Single amino acids will elicit certain effects like the increase of growth hormone, IGF, testosterone, and nitric oxide production. 
    • Collagen is a special protein. It is a connective tissue making up a third of the protein in our bodies.

    Protein is required for our repairing of cells, the growth, and for maintenance. another use is the production of enzymes, hormones, and DNA. Protein is found in many shapes and sizes and put into two main categories, conjugated and simple proteins. Protein makes up the vast majority of dry weight of the body cells. Some of the major properties of the proteins are transportation, contractile roles, hormone production and use, structural roles, receptor roles, and enzymes. 

    The Amino Acids

    The amino acids are put in classifications based on their need in the diet by the body. we have three different categories we use. Indispensable amino acids are the ones that the body can’t synthesize, and they are needed in the diet. Conditionally indispensable amino acids are the ones that are requiring a source when the rate of synthesis of the body can’t meet metabolic needs. Dispensable amino acids are the last category, and these are the amino acids that can be made in sufficient levels if they need to be. These are the US terminologies. 

    The Canadian terminologies place the amino acids into two different groups. The first is the essential amino acids. these are the amino acids that we need to take into the body through diet since they are unable to be made. Then we have the nonessential amino acids, which we are actually able to produce in our bodies in some form with the use of other amino acids. 

    Proteins/Amino Acids and Energy

    It functions the same as the fats and carbs when it needs to. This only really happens in times of starvation and in times of severe restriction of calories. The body releases amino acids and proteins from the muscle tissues for use as energy or in the energy cycles if needed. This protein catabolism happens sometimes in times of high intensity exercise. 

    Even when an athlete has a good diet, the body will still use some amino acids as fuel in big bouts of exercise. The muscles use branched chain amino acids for the supply of limited energy in the hard exercise bouts. These three amino acids alone can be used over the use of other protein when needed. Leucine is used more so than the other two BCAAs. 

    Rating the Quality of Proteins

    Just like the carbs, we see differences in the proteins we take in. Not all protein is equal. 

    Complete Versus Incomplete Proteins

    The compete proteins are going to be the ones that have essential or indispensable amino acids in the levels that are good enough for normal growth and boy weight maintenance. indispensable amino acids again, are the ones we are not able to produce. 

    Incomplete proteins are going to be proteins that do not have at least one of the indispensable amino acids. this deficiency makes a condition that is limiting, and adversely affects the growth and development rates.

    Protein Efficiency Ratio

    This is another way to find the quality of some protein. The PER is calculated with lab animals. It refers t the weight gained and the amount of protein that is taken in. an example is looking at casein protein. Here we see a PER of 2.86, showing that for every 2.86 grams of weight taken on, it only takes 1 gram of the casein protein. 

    The main criticism with this PER method is that it looks at testing on animals and not humans, so it must be somewhat off. 

    Net Protein Utilization

    This is a way we can find how digestible the proteins are. It is done by measuring how much nitrogen is taken in from the amino acids in a protein. The more nitrogen we see absorbed, the more digestible the protein is. 

    This is calculated by measuring someone’s nitrogen intake from amino acids and then having a comparison of the nitrogen put out by the body and seeing how much is needed to balance those two levels. 

    Biological Value

    These have not been entirely standardized, but there is one method that scientists prefer most. The general formula is nitrogen retained divided by the absorbed nitrogen and then multiplied by 100. This gets you the BV. 

    It does not actually show the fat of the amino acids on the body, just the use of nitrogen and nothing else. So, it is not a favorite for assessing proteins and amino acids. 

    Amino Acids Score

    This came about in response to the other testing being limited in that they just look at specific things that might matter less. This method relies on assessing the score of proteins based on the amino acids they contain. 

    Protein Quality for Athletes

    Ingesting the highest quality proteins based on those ratings systems is going to be needed. Protein and amino acid supplements are going to be used for fortifying diets to help the total need for proteins and specific amino acid needs. Along with the basic needs of proteins, there is an increased ingestion for certain amino acids for boosting the processes of metabolism.

    Nitrogen Balance

    The balancing of nitrogen has been looked at quite a bit in research. Nitrogen is what makes the amino acids different and what distinguishes protein from the other macronutrients. The nitrogen balance simply means that the same amount of nitrogen is entering the body as the amount that is leaving the body. a negative balance could show the cannibalization of the muscle tissues. All athletes should aim to balance this. 

    Designing Protein and Amino Acid Products

    Amino acid profiles are put as one of the main things to look for when making a product. Most products will have a wide variety of the amino acids. 

    Another major factor to look at for products is going to be the rate of absorption of the proteins and amino acids. the faster the rate of absorption, the quicker it can get through the body. 

    The main point regarding quality of proteins is that some sources just have a naturally greater quality than others and by combining or adding amino acids, the quality of the diet can be improved significantly. 

    Free Form and Peptide Bonded Amino Acids

    When looking at the content of amino acids for the food and supplements, we use the terms peptide bonded and free form. 

    The free form amino acids are the ones that are in a free state, or simply alone. When the protein is taken in and digested, some amino acids will be put into free forms for transporting easily around the body. Di-peptides will be when there are two linked amino acids together. Tri-peptides are the three linked amino acids and then anything more than that will be called polypeptides. 

    Hydrolyzed proteins are a protein that is broken down by enzymes and mixes with the free form, di-peptide, and tri-peptides. 

    Digestion of Protein and Amino Acids

    The actual mechanical digestion starts as always in the mouth when we are chewing our food. from there it goes to the stomach where pepsin is an enzyme that joins in to break the proteins into smaller segments. They will then go into the intestines, where they will be absorbed in forms as big as tri-peptide, but usually smaller than that. The enzymes will continually digest the polypeptides into smaller forms as they travel down the intestines.

    When the amino acids enter the bloodstream, they will be moved to the liver and a few things happen then. They are possibly going to be made into other amino acids or proteins. They might be used for further breakdown and or used as energy. Another option is for them to enter the circulation system and be used by a cell elsewhere in the body. 

    The proteins leave the stomach in 2 – 3 hours or more depending on the amount of fat or the amount of food that is taken in. this means, it is often a good idea to limit the fat in your food when you are trying to maximize your body’s use of protein.

    Amino Acid Review

    Alanine and Beta-Alanine

    Alanine is indispensable and found in a high quantity within the muscle tissues along with the dispensable amino acids due to the ability to manufacture them. Alanine plays an important role in biochemical processes during times of training. 

    Beta-alanine is a new part of the sports supplements we see on the market. It has gained its popularity due to many clinical researches done that show it as a benefit and promoter of performance benefits for athletes. 


    This is a conditionally indispensable amino acid that plays a critical role in many metabolic factors that are extremely important for athletes. Arginine is more popular for the role of stimulating growth hormone for humans and IGF levels. It is shown to increase these levels of hormones.


    This is an amino acid that is dispensable and made in the body from aspartic acid. It is involved in things such as the nervous system functioning and preventing nervousness and extreme calmness. 

    Aspartic Acid

    This is a dispensable amino acid that reduces the level of ammonia in the blood following times of exercise. It is naturally found in plants and animals. 

    Branched Chain Amino Acids

    These are the three amino acids of Leucine, Isoleucine, and Valine. 

    These are three indispensable amino acids that make up around 35% of the content of amino acids within muscle tissues. Leucine has been viewed as the most important of the three by far. It is two times more often found than isoleucine and valine. 

    Some benefits relating to exercise and the BCAA supplements are:

    • Increases in endurance for the individual.
    • Reduction in the amount of fatigue experienced. 
    • Mental performance has been shown to go up along with increases in the level of energy.
    • Protein synthesis is stimulated.
    • We see improvements in the balance of nitrogen. 
    • We see improvements in the function of our immune system due to the role of those three amino acids.
    • We see increases in the amount of lean body tissue and an associated increase in strength.

    Leucine, a Key BCAA. 

    Leucine has been seen as one of the most crucial BCAAs and this is due to the effect had on energy production and on the major role of synthesis of proteins. These are vastly important in exercising for obvious reasons. 

    BCAAs Help to Increase Training Strength, Endurance, and Muscle Mass

    Many studies have involved bodybuilders of varying ages, and they have found that the groups experienced increases in body weight and of course more so in all of the groups using the BCAAs. This was mainly in the increases in the lean body mass. Strength gains were made along with this, as it often happens when we are gaining lean body mass. 


    This is a dispensable amino acid with a main role in the urea cycle to remove the ammonia found within our blood. The research is evolving quite a bit and has not been perfectly discovered yet. 


    This is a conditionally dispensable amino acid based on sulfur. The body makes this from both methionine and serine. It is important for our production of hair, proteins, connective tissue, insulin, and taurine. 


    This is another conditionally dispensable amino acid like the cysteine. It is made from two molecules of cysteine. 

    Glutamic Acid

    This is also known as glutamate, and it is a dispensable amino acid that is found in protein. It is part of the Krebs cycle and it is important for metabolism of carbs.


    This is a conditionally dispensable amino acid that we find in our proteins in the diet and it is manufactured in the body when the need is there. It is one of the more plentiful amino acids found in the body. 


    This is a conditionally dispensable amino acid that is made from serine. Folate acts as the coenzyme. It is a good precursor for many bodily substances.


    This is an indispensable amino acid that is important for repair and growth of our tissues. 


    This is one of the popular and useful BCAAs and is needed for hemoglobin. 


    This is another indispensable amino acid that we find in large amounts in the muscle tissues around the body. we need it for proper growth and development of our bones. It also helps us with the absorption of calcium.


    This is another indispensable amino acid that bears sulfur. It plays a role in transmethylation, which is the metabolic process for which an amino acid gives a methyl group to some other compound. 


    This is a dispensable amino acid that is not found in proteins. The main role here is going to be through the urea cycle, making it vital for the removal of ammonia from the blood.

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    This is an indispensable amino acid and a precursor for tyrosine, which is not an essential amino acid. 


    This is an amino acid that is conditionally dispensable. It is found in great amounts within the collagen in the body. it is made form and also potentially changed into glutamic acid. 


    This is an amino acid that is dispensable and found in proteins and may also come from glycine, another amino acid. The metabolism of this amino acid leads to forming many vital substances like choline and some phospholipids. Those are both essential for forming neurotransmitters and used to stabilize the cell membranes.


    This is an amino acid that is dispensable and sulfur bearing. It works to play a big role in our brain tissues and the function of the nervous works in the maintenance of blood pressure regulation and transporting the body’s electrolytes in the cell membranes. 


    This is an amino acid that is indispensable and found in proteins. It is important for our tooth enamel, for other proteins, elastic tissues, and for collagen. 


    This amino acid is indispensable and needed when producing the vitamin B3 and serotonin. Both are important in the body.


    This is an indispensable amino acid made from phenylalanine, another essential amino acid. 


    This is the last amino acid. It is indispensable and a member of the branched chain amino acids we discussed before. 

    Special Protein and Amino Acid Needs of the Athlete

    Simply having a fixed goal amount of protein is not enough when you are an athlete looking for the best results. We need to look at the roles that all of the amino acids play, and the quality of the food that we are taking in. 

    We can use the protein guidelines as a baseline, but it does not stop there. Another thing to consider is the need for more protein when we are kids and developing. 

    Depending on the sport of choice for the athlete, there are requirements found to be about 1.5 – 2.5 grams per kg of body weight for the adult athletes. Even then, a bodybuilder might even require as much as 3 grams per kilogram. Which is significantly more than the RDA. And, excess protein is not going to be converted into muscle tissue, instead it will be used for energy or for fat storage. So, we cannot simply take in crazy amount of protein without having some problems. 

    Food and Supplement Sources of Protein

    These proteins are of course found in both plants and animals, and in the case of the animal protein, this usually implies the intake of fat with it. Most of the plant sources are less beneficial and are usually going to be more incomplete proteins, than that of their animal counterparts.

    Whey Protein Gets Results, Too

    This is the most expensive main protein in protein products, and it has some distinct advantages over others. It enhances the amount of glutathione production. It has a high amount of the important BCAAs. It also contains a significant amount of essential and nonessential amino acids. it is one of the most complete proteins we use in powder form. 

    Estimating Daily Protein Requirements

    The usual charts and calculations use a dynamic approach to find what someone’s needs are. This is based on their lean body mass and their activity level. 

    Summary of Proteins and Athletes Relationship

    Athletes require around 2 – 3 times the DRIs for protein.

    Ideally, the requirements need to be calculated based on lean body weight of the person. 

    The highest quality proteins possible should be a large part of the diet.

    Protein supplements and tablets of amino acids need to be used for fortification of the dietary proteins from the food sources.

    Protein should be taken in with each meal, but not right before events.

    BCAAs can be taken to fortify food proteins and during exercise to possibly spare the muscle tissue from being used as energy. Protein powders can be used also.

    Calcium and vitamin B6 need to be increased for athletes that have diets high in protein and need to be a part of the formulations of amino acids for growing muscles and recovering from work. 

    Amino acids individually should be taken in combo for releasing hormones, detoxifying from ammonia, relaxing, and simulating. 

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