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Everyone talks about it. In gyms, magazines, bodybuilding forums and health food shops they're all talking about it. So what's all the fuss about protein?
Everyone who uses weights has heard about the food group called; protein, but most just think that if they have a protein drink in the day then that will be good enough for their diet. How many times have you heard people say when they are asked “how many calories are you on a day”, or “how much protein do you take in a day”. And how many times have you heard “haven’t got a clue” or “don’t know”. And when these people are asked “why don’t you work it out” the reply comes back “can’t be bothered”. Most do not realise that they maybe training for many months and sometimes years without realising the importance of their intake of protein and other food sources for recovery and growth, immune system etc.
Protein is so important for building and maintaining tissues and for making hormones and enzymes that burning it up as a fuel is wasteful. When protein is burned as fuel, the nitrogen must be removed from the amino acid chains and excreted. When you increase the excretion of nitrogenous wastes, you also increase the amount of water lost as urine. So you waste protein by burning it up, and you risk dehydration because of the increased volume of water that is lost when nitrogenous wastes are excreted. High protein diets are also shown to increase the excretion of calcium in the urine. Females need to be aware of this because of the risk of osteoporosis (Brittle bone disease) later in life.
When dietary protein is consumed it is digested into small protein molecules called polypeptides and eventually into individual amino acids. The amino acids are then absorbed into the blood and transported to different tissues where they are manufactured into necessary proteins. To ensure that the tissues are capable of manufacturing needed proteins, the essential amino acids must be present for protein synthesis to take place.
It is therefore important that we supply the body via our food so that it has the widest possible array of essential amino acids which will allow the tissues to synthesise the amino acids needed for optimum body function. The liver is the central processing unit for protein synthesis; it continually monitors protein needs and synthesising amino acids and proteins to satisfy a variety of bodily needs. This protein synthesis is accomplished through two processes called transamination and deamination reaction. In transamination the nitrogen from one amino acid is used for the manufacture of another amino acid. In deamination the amino group is removed from the amino acid and converted to ammonia. The remaining carbon structure is then either reconstructed as fat and stored, or converted to glucose, or burned for energy. Once all our protein needs are met by the body all of the remaining amino acids are disposed of by deamination. The ammonia created by the deamination process is toxic but enzymes in the liver convert the ammonia into urea which is then excreted from the body in the urine. So we can see that excess protein that is consumed and not used by the body can cause a greater production of ammonia that must be removed form the body. The majority of the remaining deaminated carbon chains are then stored as fat.
So when amino acids are not being used to build protein or make other nitrogen-containing compounds, amino acids are “wasted” in a sense. This wasting occurs under any of four conditions: (1) when there is not enough energy from other sources: (2) when there is too much protein. So that not all is needed: (3) when there is too much of any amino acid from supplements: (4) when the diet’s protein is of to low quality, with to few essential amino acids. To prevent the wasting of dietary protein, and permit the synthesis of needed body protein, three conditions must be met. First, the dietary protein must be adequate in quality. Second, it must supply all essential amino acids in the proper amounts. Third, enough energy yielding carbohydrate and fat must be present, to permit the dietary protein to be used for body requirements and not for energy. Remember that carbohydrates are protein sparing and conserves tissue protein.
Note: There is no evidence that protein intake higher than the amounts mentioned above (for example, 2.0grams of protein per kilogram of body weight per day) accelerates the rate of muscle protein synthesis
So let’s look at protein in a bit of depth...
Some of us will have heard about being in “Nitrogen Balance”. You might of read it somewhere in a magazine but what is it? Nitrogen balance is the difference between our intake of protein (which is compound containing nitrogen) and the loss of nitrogen in faeces and also in our urine. You may know that exercise burns approx 10 – 15% of the total amount of calories from protein by extracting particular amino acids from muscle tissues. If the intake of protein is less than which is required by the body due to normal bodily uses and training then lean muscle tissue will be sacrificed through a process called gluconeogenesis. (The conversion of protein or fat into glucose)Protein is so important for building and maintaining tissues and for making hormones and enzymes that burning it up as a fuel is wasteful. When protein is burned as fuel, the nitrogen must be removed from the amino acid chains and excreted. When you increase the excretion of nitrogenous wastes, you also increase the amount of water lost as urine. So you waste protein by burning it up, and you risk dehydration because of the increased volume of water that is lost when nitrogenous wastes are excreted. High protein diets are also shown to increase the excretion of calcium in the urine. Females need to be aware of this because of the risk of osteoporosis (Brittle bone disease) later in life.
Protein Metabolism:
Protein is composed of Carbon, hydrogen, oxygen nitrogen, and is the only nutrient that contains nitrogen which makes it both essential and potentially toxic. Amino acid building blocks constitute the larger structures of protein. Some of these amino acids can be synthesised from other amino acids, (referred to as non-essential amino acids) While some must be obtained from the foods that we eat (referred to as essential amino acids). When we see the words non-essential it doesn’t mean that we don’t need them, as both essential and nonessential amino acids are equally important and both are equally essential in the human metabolic processes.When dietary protein is consumed it is digested into small protein molecules called polypeptides and eventually into individual amino acids. The amino acids are then absorbed into the blood and transported to different tissues where they are manufactured into necessary proteins. To ensure that the tissues are capable of manufacturing needed proteins, the essential amino acids must be present for protein synthesis to take place.
It is therefore important that we supply the body via our food so that it has the widest possible array of essential amino acids which will allow the tissues to synthesise the amino acids needed for optimum body function. The liver is the central processing unit for protein synthesis; it continually monitors protein needs and synthesising amino acids and proteins to satisfy a variety of bodily needs. This protein synthesis is accomplished through two processes called transamination and deamination reaction. In transamination the nitrogen from one amino acid is used for the manufacture of another amino acid. In deamination the amino group is removed from the amino acid and converted to ammonia. The remaining carbon structure is then either reconstructed as fat and stored, or converted to glucose, or burned for energy. Once all our protein needs are met by the body all of the remaining amino acids are disposed of by deamination. The ammonia created by the deamination process is toxic but enzymes in the liver convert the ammonia into urea which is then excreted from the body in the urine. So we can see that excess protein that is consumed and not used by the body can cause a greater production of ammonia that must be removed form the body. The majority of the remaining deaminated carbon chains are then stored as fat.
So when amino acids are not being used to build protein or make other nitrogen-containing compounds, amino acids are “wasted” in a sense. This wasting occurs under any of four conditions: (1) when there is not enough energy from other sources: (2) when there is too much protein. So that not all is needed: (3) when there is too much of any amino acid from supplements: (4) when the diet’s protein is of to low quality, with to few essential amino acids. To prevent the wasting of dietary protein, and permit the synthesis of needed body protein, three conditions must be met. First, the dietary protein must be adequate in quality. Second, it must supply all essential amino acids in the proper amounts. Third, enough energy yielding carbohydrate and fat must be present, to permit the dietary protein to be used for body requirements and not for energy. Remember that carbohydrates are protein sparing and conserves tissue protein.
Protein Requirements:
Protein contains 4 calories per gram which is the same amount of calories that we get from carbohydrates. The recommended protein intakes are:-| Population Group | Protein Requirements |
| Sedentary men and non-pregnant women | 0.8g per kilogram of bodyweight |
| Male and non-pregnant female recreational athletes | 1.0 – 1.5g per kilogram of bodyweight |
| Endurance trained athletes | 1.2 – 1.6g per kilogram of bodyweight |
| Strength trained athletes | 1.4 – 1.7g per kilogram of body weight |
