Protein
The Basics
Protein is digested by the body and broken down into chains of amino acids which constitute the building blocks for the body to maintain body tissue and grow. It supplies the body with 4 calories per gram.
Good Sources of Protein
- Lean meat
- Eggs - but beware of saturated fat and cholesterol in the yolks
- Low fat milk and other dairy in moderate quantities
- Beans and legumes including soy
- Nuts but beware that they are also high in fat
- Commercial Protein Supplements
What does Protein do?
There are 20 types of amino acids in total and the body can only naturally synthesise 11 of them. The remaining nine are referred to as the essential amino-acids. The body breaks protein down into these amino acids in the stomach and small intestine.
The percentage of the protein the body can use to synthesise the amino-acids it needs will affect the quality or bio-availability of the protein. The protein in eggs and meat has in the past been referred to as a 'complete' protein because it contains all the essential amino-acids and thus has a high bio-availability. In simple terms, the body can use more of the protein for muscle growth and repair.
Although many good sources of protein are incomplete in the sense that they do not contain all the essential amino acids to make them very useful for the body, they can be combined with other foods to provide all the essential amino acids and thereby produce a 'complete' protein meal. The importance of this is disputed and it is now thought that any diet containing a variety of sources of vegetable proteins will be likely to provide sufficient amino acids and that complementing vegetable proteins at every meal is unnecessary. Nevertheless, a vegetarian athlete would be well advised to educate themselves more thoroughly on this subject.
If a person consumes more protein than they need, it will be broken down and stored as fat. This is a one way process, so it is worth remembering that for optimum functioning the body needs regular moderate sources of protein throughout the day rather than fewer larger sources, which may exceed the body's requirements and will then simply be stored as fat.
Protein is a major component within our bodies making up much of our cell walls, muscles and organs.
How much protein do I need?
Short answer: Aim for about 30% of your total calories to come from protein. If you do resistance training you can increase your protein intake, and consider doing so by consuming essential amino acids with a little carbohydrate very soon before or after training.
The Detail:
Worldwide health recommendations for minimum dietary requirements for protein consumption are surprisingly low. The American National Research Council recommends 50-65g of protein a day which may be as little as 10% of total calories. This translates to about 0.8 grams of protein per kilogram of bodyweight for a 62.5kg individual. These Minimum dietary requirements for maintenance of lean body mass in a sedentary population equate to the minimum amount of protein needed to survive and not go backwards.
But the human body is remarkably resilient and adaptative and appears to be able to maintain lean body mass without increases in protein intake, even when significant training is involved. What is more important is that total caloric intake is sufficient once the protein minimums are met.
Many diet plans ramp up the amount of protein in a diet both in absolute terms and as a percentage of total calories. When meat sources of protein are used, there can be a risk of a commensurate rise in intake of saturated fat and bad cholesterol, LDL.
We are here also interested in what the optimum level of protein intake is, in order to thrive. The scientific community has not yet come to a definitive view as to whether significantly more protein is required by athletes and therefore aren't certain to whether to recommend it.
People who are putting their muscles through intense exercise appear to require more protein than sedentary individuals and these requirements will change dynamically along with the particular uses an individual is putting their body through at a particular time. There is some research to suggest that athletes' bodies adapt to their muscle's increased activity and over time either become more efficient in harnessing the protein they ingest, or make subtle changes to body metabolism when they are not exercising, to maintain a balance without the need for increased protein.
An athlete trying to create protein accretion, primarily through muscular hypertrophy (getting more muscular), will need to combine their training regime with a protein (and small caloric) surplus capable of providing the body with the amino acid building blocks for growth.
Endurance athletes and sportspeople not desiring to increase their lean body mass may still benefit from additional protein to repair the muscles they are using more heavily than the sedentary person but it is not yet clear just how important this is. The increased exercise creates an increased total caloric intake, which in turn increases the absolute protein intake.
It may be the case that an athlete will increase their caloric intake but those who are concerned to maintain lean weight may do so by increasing the percentage of their total calories which they are ingesting from a protein source in order to still achieve the necessary protein intake without over consuming calories. This is, in effect, a form of the high protein, low carbohydrate diets that have spread into the mainstream.
Creating the right nutritional conditions for muscle growth in any interested person can be of benefit from an aesthetic and general health perspective and people should not be concerned that increased general exercise and protein intake will turn them into muscle bound freaks. Moderate increases in lean body mass have significant long term health benefits which can only be gained by creating conditions for protein accretion.
There is little evidence of any detrimental effects in otherwise healthy people of increased protein intake up to as much as 2.5-3 grams per kilogram of bodyweight (assuming there is no increase in saturated fats or other harmful substances). But this is an extremely high amount and may cause a restriction in other essential nutrients found in other foods. Such a high intake of protein would not be necessary except for very active resistance trainers and amounts of between 1.2-1.7g per kilogram will meet most people's needs. Another way to consider it is to aim for approximately 30% of caloric intake to be from protein, which is part of the famous 40:30:30 diet. (40% carbs, 30% protein, 30% fats).
It is worth noting at this stage that it is simplistic to speak purely of total protein intake when the quality and timing of the intake will also influence outcomes. This is discussed further below.
Timing of intake
Numerous clinical studies on humans have shown that intake of essential amino acids directly following resistence exercise increases muscle protein synthesis (essential for muscle growth). The amount required is relatively small and may be as little as 6g of essential amino acids. But bear in mind that in a regular meal and even in a supplement there will be many other ingredients and amino-acids as well, hence the reason many dosages will be 30g or more in total.
This comes as no surprise to body builders who almost to a man (and woman) will swear by the need for an immediate protein shake or meal after training. That wisdom built up over years within the fitness community and well known prior to the availability of complex clinical testing, now has solid scientific backing.
Intake of carbohydrates following resistence training has been shown to ameliorate the negative protein balance existent within the body, but not enough to create the positive balance necessary for muscle growth. It seems therefore that an oprimum post workout consumption will include both essential amino acids and a component of carbohydrate.
Studies have now surfaced which show that a pre-workout intake of essential amino acids and moderate carbohydrate can also create the positive balance necessary for muscle development. It is unclear which is preferable at this stage and many body builders do both. The pre-workout consumption also has the effect of increasing caloric energy levels for the workout itself.
Bottom Line:
There is still a long way to go in our understanding of protein requirements in active humans. There is little risk in increasing our protein intake above the minimum requirements as long as it doesn't involve consuming other harmful substances and other essential nutrients are also being consumed in adequate quantites. Athletes, particularly those wishing to gain lean muscle, should consume essential amino acids and moderate carbohydrates immediately before or after exercise.
Sources:
Essentials of Human Nutrition, Third Edition, Oxford University Press
http://en.wikipedia.org/wiki/Protein_(nutrient)
Arnold Schwarzenegger, The New Encyclopedia of Bodybuilding
http://www.nlm.nih.gov/medlineplus/ency/article/002467.htm
http://www.vegsource.com/attwood/complete_protein....
http://en.wikipedia.org/wiki/Protein_combining and source material referred to therein
http://www.cdc.gov/nutrition/everyone/basics/protein.html
http://www.uni.edu/dolgener/Advanced_Sport_Nutriti...
http://www.merckmanuals.com/home/disorders_of_nutr...
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