There are many controversial theories about protein as it pertains to fitness.  How much do we need?  When should we consume it and what kind should we eat?  How much muscle do I lose when I diet or train?  Those are all great questions and I hope to shed some light on questions that you might have as well.  Lets take a look at some of the processes that proteins are involved in and what happens to our muscles and proteins throughout our day.  This is a big subject and it is my intention to offer you information so that you may better support your health and fitness by optimizing your intake of carbohydrate, protein, and fat.  

What is protein?

Protein is, by definition, a molecule consisting of one or more polypeptides.  A polypeptide is a polymer of many amino acids linked by peptide bonds.  So in short, a protein is a bunch of amino acids all linked together with special bonds.

What does protein do for us?

Proteins serve the body as building blocks in the growth and repair of tissues, as enzymes in metabolsim, as hormones, as regulators of the bodies fluid balances, as antibodies, and in many other ways.  So you can see that protein is vital to the maintenance of optimal health.  Proteins themselves are constantly being synthesized or broken down as needed almost everywhere in the body.

Where do I get these?

Amino acids are the primary ingredient in proteins which as we know are the building blocks for our bodies to maintain and increase strength and various metabolic functions.  All of the proteins we consume contain amino acids in various concentrations.  Not all protein sources contain all of the amino acids.  

Limiting amino acids

The human body has no storage site for extra amino acids and to make a protein, a cell must have all the necessary amino acids available simultaneously.  The liver can produce any non-essential amino acids that may be in short supply but if an essential amino acid is needed, the body can and will dismantle its own protein to continue making proteins.  The body makes complet proteins only.  If there is one amino acid missing, the others cannot form a "partial" protein.  The amino acids are used for other purposes or wasted.  An essential amino acid supplied in less that the amount need to support protein synthesis is called a limiting amino acid.
 

Essential  amino acids

Essential amino acids are those amino acids that the body cannot produce on its own either at all or in sufficient quantity.  They must be ingested and are absolutely necessary to maintain health.  They are Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, and Tryptophan.  Tryptophan is the precursor to Seratonin by the way so you can imagine what will happen if you do not ingest proper amounts of Tryptophan....  depression.  If the body is not supplied by a diet with adequate essential amino acids, it will break down proteins (I.E. Muscle) for use in creating new proteins.  This is called protein catabolism.

Non-Essential amino acids

A non essential amino acid is an amino acid that can be produced by the liver in the absence of dietary non essential amino acids.  This is done by utilizing fragments of carbohydrate and fat that is available in the system and nitrogen to form the amino group.  Non essential amino acids are usually found in the diet but in unusual circumstances they can be produced internally.

The non essential amino acids are;  Alanine, Arginine, Asparagine, Aspartic acid, Cysteine, Glutamic acid, Glutamine, Glycine, Proline, Serine, and Tyrosine.

Protein as a fuel

Protein can be used as a fuel source if the body is starving for other more desirable fuel sources such as carbohydrate and fat.  When glucose or fatty acids are limited the body is forced to to use amino acids for energy and glucose.  The body does not make a specialized storage form of protein as it does for carbohydrate and fat.  When the need arises the body dismantles its tissue protein (I.E. Muscle) and uses them for energy in the form of glucose.  Although this use of protein for fuel occurs very slowly, lean body mass will be "wasted' in the process.  Typically in a healthy adequate diet, only very small amounts of protein is wasted.  This is why such a small percentage of dietary intake (10-15 percent) need be in the form of protein.
 

Deaminating amino acids

When amino acids are broken down as in the case of providing energy, they are first stripped of their nitrogen containing amino groups.  Deanimation produces ammonia, which the cells then release into the blood stream.  The liver picks up the ammonia, converts it into a less toxic compound (urea) and returns the urea to the blood.  Now it does not take much to see that this is quite a bit of toxicity in the body so protein breakdown would best be avoided if at all possible.  The kidneys then filter the urea out of the blood in the urine.  This of course can be measured in the urine so many tests on toxicity and protein catabolism are done with urine samples.

How much protein should I consume?

This is the million dollar question when it comes to protein.  Fortunately most Americans consume at least enough, if not too much, protein each day.  Roughly 10-30 percent of your daily intake of calories should come from protein.  Meaning that a 2000 calorie per day diet would offer 200-600 (50g-150g) of those calories from protein sources.  Different studies have ended with different results which is why there is such a variance in the percentages recommended.  The U.S. RDA is .8 grams per Kilogram of appropriate body weight.  Appropriate simply means that an obese person would be best served to eat the amount of protein recommended for him if he was at a more common, healthy weight.  The diet and health report recommends that people maintain a protein intake that is between the U.S. RDA and twice the U.S. RDA. It appears that having slightly higher protein intake does not do damage although excessive protein intake can be very damaging. 

How much food is that?

A single ounce of meat delivers about 7 grams of protein so you can see how easy it is to consume an appropriate amount of protein each day.  75g of protein would be consumed by eating 6 ounces of chicken, fish or beef at one meal, a glass of milk at breakfast and three servings of vegetables during those meals.  Typically in developed countries, there is very little protein deficiency found.  

Can I have too much protein?

Yes you can absolutely consume too much protein. There are many health issues surrounding excessive protein consumption.  I am going to list a few of the more easily understood concerns.   Calcium excretion rises as protein intake increases and that is especially true with the intake of animal sources of protein.  Excessive calcium loss can lead to Osteoporosis.  Excessive protein that is consumed has to be broken down and is then stored as fat if it cannot be utilized by the system.  This creates higher fat deposits.  Many proteins are associated with animal products and this increased consumption of animal products can lead to a higher fat intake and higher risk or heart disease.

Wrapping it up

Although this can all sound so confusing, it is really much easier than it sounds.  Simply eat smaller amounts of lean protein (3-4 ounces) two to three times per day and you will do just fine.  Plenty of building blocks in the system with little worry for excessive intake or mineral loss.