Protein Metabolism Made Easy

When we want to add muscle, the first thought is usually consuming more protein. Want to lose weight? - more protein. But how much should we actually be consuming every day and what type and why do we actually need it? This article aims to simplify protein metabolism and identify what quantities are needed and the best forms to take in in our diet.

Let's begin with defining what a protein actually is. Protein, like carbohydrates and fats, is made up of carbon, hydrogen, and oxygen but with the added nitrogen atom, which in turn creates amino acids. Amino acids are the building blocks of protein and are bound together by peptide bonds creating what is known as a polypeptide. A protein is made up of hundreds of possible combinations and compounds of amino acids and can contain up to 300 peptide bonds per protein. There are 20 amino acids, 11 non- essential, which can be synthesized in the body and 9 essential amino acids, which cannot be synthesized in the body. These essential amino acids need to be digested through our diets and supplements. The most important essential amino acids are known as BCAA’s (Branch chain amino acids) and contain leucine, isoleucine and valine and these three compounds make up 20% of our bodies protein content.

What is the role of proteins in the body?

Protein plays an important role in the body; we don’t just need it to get bigger muscles and to help recovery. However, muscles do contain 40% of the body’s total protein content with actin and myosin (responsible for contractions and sliding filaments for movement) having 80-90% of the muscles protein. Adequate protein levels are needed for things such as transportation of red blood cells and albumin; the hormonal balance of adrenaline; contractile elements of actin and myosin and energy balance of the TCA cycle. 

Protein is in a constant state of turnover, with new proteins being built continually (through synthesis). Because of this constant turnover, 20% of our basal metabolic expenditure is a result of this. Before we can utilize the protein we have eaten it needs to be digested. This process begins in the stomach, where pepsin is released to break down the protein. The protein then moves into the small intestine where Trypsin, Chymotrypsin, Carboxypeptidase, and Elastase break it down further into our amino acids. The amino acids then move to what is known as the pool of amino acids. From here it will either be synthesised or oxidised. If the protein is synthesised they are turned back into new strands of protein and are used to make new body tissue, enzymes, hormones, and antibodies or to repair any muscle damage and repair white blood cells.

What happens to the leftover amino acids?

The leftover amino acids can then be used for gluconeogenesis (creation of glucose from protein), ketogenesis, and lipogenesis and in extreme circumstances used for energy. The proteins not used will then get put back into the pool of amino acids through a process called degradation. From there the amino acids undergo transamination where the amino acids are broken down further and oxidised by removing a bond creating a keto-acid. This is then taken to the TCA cycle to provide energy and will enter the TCA cycle at different points dependent on what keto acid they are. The other option is for the amino acid is to be turned in to ammonia. Ammonia is toxic to the body, therefore, is pushed into the urea cycle and excreted. I’ll break this down into three types of individuals; sedentary, people participating in exercise and people losing weight.

Individual	Protein required per kilo of mass	Example of 80kg man’s intake	How many calories is this?
Sedentary	0.8g.kg.bm	64g	256kcals
Active	1.2-1.8g.kg.bm	96-144g	384-576kcals
Losing weight	1.8-2.3g.kg.bm	144-184g	576-736kcals

Upon looking at these levels I’m sure some of you will be thinking that they are quite low on the protein side, but you don’t need more than these levels as your body cannot utilize such high numbers and without sounding crude you will be peeing it all out because of this! I would suggest at a push going to 2.0g.kg.bm  (kilograms per bodyweight) if you so wish but not any higher unless you are cutting/losing weight (Losing weight has the highest intake level for various reasons which are highlighted in more depth in my ‘the ins and outs of losing fat’ article) as you will be wasting valuable calories that could be better used on carbohydrates and fats.

Now moving on to what types of protein are best for our needs? This is a topic that is talked about often and people will have varying opinions on this. There are two types of whole protein that we get from our diet ‘complete’ and ‘non-complete’.

Complete proteins vs. incomplete proteins

Complete proteins contain all of the essential amino acids and are found in foods such as poultry, beef, fish, and dairy and in supplements such as whey protein and BCAA’s. During exercise, leucine synthesis is increased and therefore needs to be replenished once finished.

This can be done so by ingesting a complete protein source. A good example of this is a whey protein as this has a BV (how much protein is absorbed from food) and contains high levels of leucine. If this is not possible any complete source of protein will be fine.

Incomplete protein sources often contain few if any essential amino acids and are often plants based food, e.g. grains and vegetables. If you are a vegetarian do not worry as by combining different sources of this incomplete proteins together you can, in fact, create a complete protein.

Is that it?

This isn’t easy work but can be achieved if combining you food cleverly.  You may notice that I have not added pork product up to this point, this is because although it is a ridiculously tasty animal it does not offer us much in terms of complete protein. The amino acid profile is not as good as other sources and will not offer us as great macro and micronutrients that are essential for growth, recovery and health.

As a note to finish, make sure you consume enough complete protein as possible as well as adequate amounts to avoid proteolysis (muscle wastage), but not too much that you don’t utilize it and it takes the places of other important nutrients. Take advantage of the wide array of readily available sources and supplement with a reputable whey protein source containing BCAA’s for extra protein that is quick, convenient and easily digested.

That about covers it. As always Team CSN are here to help, call or email us today and we can give you professional, unbiased advice on all your nutrition and supplement needs.