Protein & Amino Acids
When it comes to designing a nutrition plan for athletes, the research has determined that there are different protein requirements for different athletically conditioned people.
Therefore, it is important to know about protein, as this is the major macronutrient needed for muscle growth and maintenance.
Protein is an essential macronutrient, which means that you must take in adequate amounts of it through your diet for continued health.
In fact, it is the basic component of all living cells and can be found in virtually every part of your body, including your muscle tissues.
This nutrient provides your body with the raw material it needs – in the form of amino acids – for tissue growth, repair, and maintenance.
Protein is also vital to the creation of biomolecules, such as hormones and deoxyribonucleic acid (DNA) – the molecule that stores your genetic code.
Also referred to as polypeptides, proteins contain anywhere from less than a dozen to over a hundred amino-acid molecules.
Amino acids are the building blocks of proteins.
Although many amino acids exist in nature, twenty-two are considered biologically significant.
The essential amino acids, the amino acids that your body cannot manufacture and therefore need to be ingested, are:
• Valine – Lysine – Threonine – Leucine – Isoleucine – Tryptophan – Phenylalanine
• Methionine – Cystine – Histidine.
Some of the nutritionally important nonessential amino acids include:
• Glycine – Alanine – Serine – Cysteine – Tyrosine – Aspartic acid – Proline
• Hydroxyproline – Citrulline – Arginine – Ornithine – Hydroxyglutamic acid
• Glutamine – Glutamic acid.
The three branched-chain amino acids (BCAA’s):
which also happen to be essential amino acids – are the preferred group of amino acids for energy use.
Scientific research has concluded that the body uses all three of these branched-chain amino acids for energy during exercise as well as during rest, but uses leucine most often.
Branched Chain Amino Acids are among the most beneficial and effective supplements in any sports nutrition program.
In the last 20 years, detailed research has enabled scientists to measure protein metabolism during exercise and recovery, and to monitor protein balance in athletes.
Endurance athletes: in heavy training require extra protein to cover a small proportion of the energy costs of their training and to assist in the repair and recovery process after exercise.
Strength athletes: who are interested in gaining muscle size and function, require more protein in the early stages of very intensive resistance exercise. However, strength athlete’s muscles seem to adapt to the stress of resistance exercise, so that the protein requirements to maintain protein balance in very well-trained athletes are only marginally greater than those of generally active people.
Athletes, who are growing, such as adolescents: have additional protein requirements.
The table below summarises protein requirements for different types of athletes or exercise activities. Since athletes come in various shapes and sizes, it is easier to keep track of these requirements by relating them to the size (body mass or BM) of the athlete.
Table 1: Estimated protein requirements for athletes
|Group||Protein intake (g/kg/day)|
|Sedentary men and women||0.8-1.0|
|Elite male endurance athletes||1.6|
|Moderate-intensity endurance athletes (a)||1.2|
|Recreational endurance athletes (b)||0.8-1.0|
|Football, power sports||1.4-1.7|
|Resistance athletes (early training)||1.5-1.7|
|Resistance athletes (steady state)||1.0-1.2|
|Female athletes||~15% lower than male athletes|
(a) Exercising approximately four to five times per week for 45-60 min
(b) Exercising four to five times per week for 30 min at <55% VO2peak
Protein may be found in a variety of food sources.
Proteins from animal sources (meat, poultry, milk, fish) are considered to be of high biological value because they contain all of the essential amino acids.
Proteins from plant sources (wheat, corn, rice, and beans) are considered to be of low biological value because an individual plant source does not contain all of the essential amino acids.
Therefore, combinations of plant sources must be used to provide these nutrients.
Eating protein after an athletic event has been shown to support muscle protein synthesis.
However, eating protein in excess of nutritional needs has not been shown to further increase muscle building.
Extra protein is broken down for energy or is stored as fat.
A varied diet should provide more than enough protein as caloric intake increases. However, vegetarian athletes should work with a dietitian to make sure their protein intake is sufficient.
Excess protein can deprive the athlete of more efficient fuel sources and can lead to dehydration.
High-protein diets increase the water requirement necessary to eliminate the nitrogen through the urine.
Also, an increase in metabolic rate can occur and, therefore, increased oxygen consumption.
It is a common myth that consuming lots of extra protein gives people bigger muscles.
Quite often, people taking part in exercise focus on eating lots of protein, and consequently may not get enough carbohydrate, which is the most important source of energy for exercise.
A modest 20g of high quality protein, equivalent to approximately half of a medium sized grilled chicken breast or a small can of tuna, has been shown to be enough for optimum muscle protein synthesis following any exercise or training session.
Any more protein than this will not be used for muscle building and just used as energy!
As well as including protein as part of a healthy, balanced diet, the incorporation of some protein after exercise is important for building new muscle tissues and repairing the damaged ones.
The following table gives examples of many basic foods that provide 10g of protein per serve.
Many people typically turn to meat, poultry and dairy products to obtain protein.
These food sources are considered to be of high value due to the protein in the food containing all the essential amino acids required to build muscle tissue.
Don’t forget that plant foods such as bread, pasta, rice, breakfast cereal, legumes, lentils and nuts also contribute significant amounts of protein to the overall diet. These protein sources are incomplete and are missing some important amino acids.
Table 2: Protein rich foods for athletes. Each of the following foods provides approximately 10 g of protein. These foods have moderate to low fat contents and are rich in other nutrients.
|Animal Foods||Plant Foods|
|2 small eggs
30 g (1.5 slices) reduced fat cheese
70 g cottage cheese
1 cup (250 ml) low-fat milk
35 g lean beef, lamb or pork (cooked weight)
40 g lean chicken (cooked weight)
50 g grilled fish
50 g canned tuna or salmon
200 g reduced fat yoghurt
150 g light fromage frais
|4 slices (120 g) wholemeal bread
3 cups (90 g) wholegrain cereal
2 cups (330 g) cooked pasta
3 cups (400 g) cooked rice
3/4 cup (150 g) lentils or kidney beans
200 g baked beans
120 g tofu
60 g nuts or seeds
300 ml soy milk
100 g soy meat
Protein Supplements Vs. Protein Foods
The biggest advantage of protein supplements is not that they can build more muscle than chicken or egg whites or any other whole food protein, the biggest advantage is convenience.
It is easier to drink a protein shake than it is to buy, prepare, and cook whole foods.
Consuming small frequent meals is the optimal way to eat, regardless if your goal is muscle gain or fat loss.
To keep your body constantly in positive nitrogen balance, you should consume a complete protein every three hours.
Aside from the convenience, the truth about protein supplements is that they offer few advantages over protein foods.
There is no scientific evidence that you cannot meet all of your protein needs for muscle growth through food.
As long as you eat every three hours and you eat a complete protein such as eggs, lean meat or dairy products with every meal, it is not necessary to consume any protein supplements to get outstanding results.
Supplemental protein (in powders, bars and drinks) is not superior to protein-rich foods, especially since many protein supplements lack essential carbohydrates, vitamins (e.g. B-vitamins), and minerals (e.g. iron, calcium, zinc) found in natural foods, hence the use of supplemental protein as an “extra” rather than as a replacement in meals.
Protein supplements, in the form of whey, casein, egg-white protein and soy, offer a portable, convenient source of protein and calories for exercise recovery or a bedtime snack, especially when combined with a mixture of milk soy drink, fruit, yogurt, ice cream or possibly juice.
Casein and egg proteins are high-quality proteins with a long track record of use in foods and supplements, but whey protein supplements are currently among the most popular and most researched of the sports nutrition supplements.
In addition to stimulating muscle growth, whey protein has been reported to increase the production of protein and glutathione – the body’s primary antioxidant enzyme, and to enhance the immune system.
Whey protein contains the essential and nonessential amino acids and is also high in the beneficial branched-chain amino acids and may stimulate the anabolic hormone, insulin-like growth factor-1 (IGF-1); a factor that is involved in muscle growth and maintenance.
The most current research indicates that whey protein isolate, which is fortified with extra leucine is the most beneficial for bodybuilders and other strength athletes.
The consumption of soy protein products benefits gastrointestinal health and help maintain healthy blood cholesterol and triglyceride levels.
A benefit of reducing blood cholesterol levels is better circulation.
This is important for general health, but also for the efficient exchange of oxygen and nutrients to exercising muscle tissues, and the clearance of metabolic waste products.
Good sources of high quality protein include:
• Whole eggs or egg whites
• Lean cuts of meat
• Low-fat dairy products
• High protein nutrition supplement bars
• Protein supplement drinks containing whey protein isolate fortified with leucine and other amino acids and nutrients
• Whey protein isolate
• Whey protein concentrate.
Another thing to remember when selecting a protein product is that it is a good idea to ingest some lipids (fats and oils) along with the protein.
The reason for this is that lipids help with the digestion of amino acids.
Therefore, eating pure fat-free protein like egg whites or fat-free and carbohydrate-free protein supplements may not be the most efficient way to ingest your protein sources all of the time.