Thread: protein Myths
03-22-2005, 04:49 AM #1
good read of the HST site
Myth#1: High protein intakes will not affect muscle protein synthesis.
Fact: Greater availability of amino acids means more protein synthesis within muscle cells.1,2,3,4,5,6,7,8
I will concede that experiments have been performed that indicate that a lab animal can survive on a very limited protein intake assuming that fat and carbohydrate intake is adequate. Simply put, the body begins to reduce that amount of amino acid oxidation in order to spare nitrogen containing compounds. Yet can we really apply this kind of example to adult humans trying to build muscle? I think not.
When the body begins getting stingy with amino acids because of low protein intake, non essential functions, such as skeletal muscle protein synthesis, drop to minimal levels. Other functions within the body such as the immune system, which uses glutamine primarily of muscle origin for fuel, also begins to suffer.9 This cripples the body's ability to cope with the stress and tissue damage induced by intense training. Researchers even believe that currently recommended protein intakes may actually predispose people to illness because of the limited reserve of amino acids. Here's what they have to say about current recommendations for protein intake:
"...It seems reasonable to conclude that the lowered rate of whole-body and perhaps muscle protein turnover that appears to occur in healthy adult subjects when intakes of indispensable amino acids approximate the current international figures, would probably diminish the individuals capacity to withstand successfully a major stressful stimulus. Again, for those reasons, we view the significant reduction in the rate of body protein turnover in healthy adults, which permits them to more closely approach or even achieve amino acid balance at currently accepted amino acid requirement intakes, as an accommodation. Thus we further conclude that these international requirement intakes are probably not sufficient to maintain a desirable or adapted state."(Young VR., Marchini JS. Mechanisms and nutritional significance of metabolic responses to altered intakes of protein and amino acids, with reference to nutritional adaptation in humans. Am J Clin Nutr 1990;51:270-89) Emphasis added.
Research clearly shows that by increasing blood levels of amino acids you increase protein synthesis in skeletal muscle. It has also been shown that you can maintain a positive nitrogen balance for extended periods of time and that nitrogen accretion will tend to continue as long as protein intake is high.10 Clearly if you want to maximize your gains in the gym you've gotta get more protein than the average Joe.
Myth #2: You can only assimilate 30 grams of protein at one sitting.
Fact: The body has the ability to digest and assimilate much more than 30 grams of protein from a single meal.
Speaking of high intakes of protein, people have been perpetuating the myth that you can only assimilate ~30 grams of protein at a time, making protein meals any greater than a 6 oz. chicken breast a waste. This is anything but true. For example, the digestibility of meat (i.e. beef, poultry, pork and fish) is about 97% efficient. If you eat 25 grams of beef, you will absorb into the blood stream 97% of the protein in that piece of meat. If, on the other hand, you eat a 10 oz steak containing about 60 grams of protein, you will again digest and absorb 97% of the protein. If you could only assimilate 30 grams of protein at a time, why would researchers be using in excess of 40 grams of protein to stimulate muscle growth?1
Critics of high protein intakes may try to point out that increased protein intake only leads to increased protein oxidation. This is true, nevertheless, some researchers speculate that this increase in protein oxidation following high protein intakes may initiate something they call the "anabolic drive".13 The anabolic drive is characterized by hyperaminoacidemia, an increase in both protein synthesis and breakdown with an overall positive nitrogen balance. In animals, there is a correspondent increase in anabolic hormones such as IGF-1 and GH. Though this response is difficult to identify in humans, an increase in lean tissue accretion does occur with exaggerated protein intakes.14,15
The take home message is that, if you are going to maximize muscle growth you have to minimize muscle loss, and maximize protein synthesis. Research clearly shows this is accomplished with heavy training, adequate calories, and very importantly high protein consumption. This means that meals containing more than 30 grams of protein will be the norm. Not to worry, all that protein will certainly be used effectively by the body.
Myth #3: Protein must be rapidly digested to build muscle.
Fact: Both rapidly and slowly digested proteins offer significant benefits to athletes.
Recent research has brought up the notion of "fast" and "slow" proteins.11 They are designated as such according to the rate at which they raise blood levels of amino acids after they are consumed. Whey protein for example is considered a fast protein and causes a rapid increase in amino acid levels. Casein on the other hand is considered a slow protein.
Both rapid and slow proteins offer benefits to someone trying to build muscle. Research has shown that proteins that enter the blood stream rapidly significantly increase protein synthesis. Proteins that enter the blood stream slowly have a pronounced effect on protein breakdown, significantly inhibiting it even at low quantities.
By using a combination of proteins that exhibit both fast and slow properties one should be able not only to jump-start protein uptake into muscle cells during a grueling workout, but also ensure that protein synthesis is jump started and that protein break down is kept at a minimum during the hours following their workout. Take the fast protein before training, and a slow protein after for maximum anabolic effect.
In summary, it is a mistake to say that a "fast" protein is better than a "slow" protein. Both types of protein should be used in strategic fashion to alter protein metabolism in favor of net protein deposition (i.e. muscle growth).
Last edited by S.P.G; 03-22-2005 at 04:53 AM.
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