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Thirty Grams of Protein Myth Thirty Grams of Protein Myth
Frontline
12-08-2006
Thirty Grams of Protein Myth

By Will Brink

It has been a long debated topic how much protein a person can digest at any one time. Nutritionists and doctors have maintained for decades that "people can only digest 30 grams at a time of protein and any additional protein is wasted or converted to fat." So say the powers that be.

Now, I wish I could examine the study or research they are basing this advice on so I could dispute it but I can't. Why you ask? Because in all my years of searching the medical data banks, talking to researchers, and falling asleep in the medical library after hours of reading, I have been unable to find exactly where this advice comes from or what it's based on.

At one time, I went so far as to offer a reward to anyone who could show me a recent study that showed that 30 grams of protein was the upper limit anyone could digest, regardless of age, weight, and activity levels.

Why is it 30 grams? Why not 28 or 35? Are we saying that the digestive and absorptive abilities of a 285 pound 23 year old football player is the same as a 50 year old 115 pound women?

Now digestion is a very complex topic. Many people think you eat some protein, it mixes with some acid or something, gets broken down into amino acids, gets taken up into the body, and everyone is happy.

I wish it were that simple. As with all foods, the breakdown of protein starts in the mouth with the simple chewing of food and the exposer to certain enzymes. In the stomach, food mixes with enzymes and other factors such as lipase, pepsin, intrinsic factor, and of course HCL (stomach acid).

It moves onto the small intestine and then the large intestine.The small intestine is considered the major anatomical site of food digestion and nutrient absorption and is made up of section such as the duodenum, jejunum, and the ileum. Pancreatic enzymes (chymotrypsin, trypsin, etc.), bile salts, gastrin, cholecystokinin, pepidases, as well as many others factors are released here.

The large intestine is composed of the ascending colon, transverse colon, descending colon, and the sigmoid colon, which all play a part in absorbing the nutrients we eat. Sound complicated? It is. Believe me, I am leaving out a great deal of information so you wont fall asleep reading my little column! Suffice it to say, digestion is a very complicated thing and there are many places along the chain of digestion that can both enhance and degrade a persons ability to absorb the foods we eat.

There is no reason to think that among this complicated process that there are not wide individual differences in a persons ability to digest and absorb protein. For some person who is inactive, elderly, and for what ever reason lives with compromised digestion, 30 grams of protein at one sitting might very well be too much for them to handle.

By the same token, assuming a 220lbs healthy athlete is unable to exceed 30 grams of protein in one sitting is neither proven by medial science or even logical in my view. So what if the 30 gram rule turns out to be true? If we examine some of the more recent studies on the protein requirements of athletes done by researchers from both the United Sates and Canada , we come to some recommended protein intakes that far exceed the RDAs, some times by as mush as 225%!

These researchers came to the conclusion that protein intakes for athletes should range from approximately 1.2 grams of protein per kilogram of bodyweight for endurance athletes and up to 1.8g of protein per kg for strength training athletes. For a 200 pound bodybuilder-a strength training athlete-that would be approximately 164 grams of protein per day (most bodybuilders I know eat considerably more protein per day, but that's for another fight and another article...). Assuming that 30 grams of protein is the most anyone can digest, absorb, and utilize, this person would have to split his intake into about five meals (164 divided by 30 = 5.47). So, given the advice by many people that 30 grams is all anyone can digest at a single sitting, it appears a person can achieve the goal of 30 grams of protein per meal even with the higher intakes recommended in the modern research (assuming they are willing or able to eat five meals per day).

However, if you happen to eat more than that per meal as a healthy athlete I don't think you have anything to worry about. I wont tell anyone. Me, I would suggest you stick to the one gram per pound of bodyweight rule, which often exceeds the research mentioned above. Also, read the "Protein Myth" article at the BrinkZone site for more info on this topic.  
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  #1  
_Wolf_ on 12-08-2006, 11:26 AM
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didnt eric already post this???
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  #2  
EricT on 12-08-2006, 03:23 PM
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The more the merrier since people will keep on asking the question!
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  #3  
TALO on 12-08-2006, 04:23 PM
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The more people read it, the more it will stick
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  #4  
Frontline on 12-08-2006, 06:45 PM
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I reposted it in the article section so more people see it, its a good response to a common question.
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  #5  
EricT on 12-09-2006, 09:34 AM
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Yeah, I should have posted it here in the first place. What he says fits what little research I've been able to do. He has many more resources than me but I have looked around and basically I found NO info on this. One way or another. It's something that people should just not concern themselves with to much.
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  #6  
Dr X on 12-09-2006, 10:55 PM
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Long standing myth and it's always good to repost.
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PRESTIGE on 09-10-2007, 11:57 AM
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If i come across any article or research showing a human body being able to digest any amount of protein per sitting, I'll be the first to up my intake per sitting. until then, 30g per serving still stands. (for me anyway)
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  #8  
casty23 on 10-21-2007, 11:02 AM
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you didn't back your argument with any science?
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  #9  
EricT on 12-02-2007, 02:49 PM
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Bodybuildings Biggest Protein Myths Debunked

Contributed by Layne Norton
Monday, 25 September 2006

Bodybuilding, more so than any other sport, seems to have developed many myths that people cling to so strongly thatthey're accepted as FACT even though there may be little or no scientific evidence supporting these myths. Protein mightpossibly have more ill-founded myths surrounding it than any other subject, probably because it plays such a large role inany nutrition program focused on building muscle. Well, the myths shall spread no further: let the debunking begin!


Myth: "You can only absorb ‘X' grams of protein in one meal."

The real deal: Not only is this myth not rooted in any kind of fact, it's actually a misnomer in and of itself. Absorption refers to the amount of a certain substance that makes it into circulation (blood) from the digestive tract. The body will
absorb a good portion of the protein you eat regardless of the amount of protein in the meal (though there's a limit to the percentage absorbed and it will vary between protein sources). What this myth actually refers to is protein/amino acid
utilization. Specifically, what's the maximum amount of protein at a meal that will be used for muscle-building processes, and at what point does the amount of protein become excessive and the extra amino acids burned for energy rather than
retained? At this point, researchers have no good answer to this question, but the answer probably depends on many various factors, including but not limited to:

- lean body mass

- length of time since last protein-containing meal

- amount of protein at previous meal

- type of protein source

- training state (Post-workout? Pre-workout? Resting?)

- total calories in the meal

- caloric balance

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Although there's no definitive answer as to the maximum amount of protein that's beneficial at a meal, there's some research out there that is mildly helpful. Leucine, the amino acid that's an anabolic component of protein1 and is responsible for stimulating protein synthesis, was administered at different doses in rats to see what dose elicited the maximum protein synthetic response.2 The researchers found that the maximum beneficial dose of leucine was achieved at 0.68 grams of leucine per kilogram of bodyweight. This equates to about 62 grams of leucine in a 200-pound
individual, which is an unrealistic amount to get from whole food. There are many problems with applying the absolute numbers from this study to a whole food meal in humans because of the differences in protein metabolism between rats
and humans. In order to determine what level of leucine at a meal elicits the greatest anabolic response for the longest period of time more human studies will be required, but the research is moving in the right direction. While there's most
definitely a maximum beneficial protein intake at a meal, no studies have directly addressed the subject and the number is likely to be influenced by various factors. So, pay no attention to Joe Dumbbell who says you can only absorb (insert
gram amount) of protein at a meal, because he has no clue.

Myth: "Don't count incomplete protein sources toward your total protein intake."

The real deal: An incomplete protein source is defined as a food lacking in one or more amino acid. I believe this myth came about in response to research that concluded that when certain amino acids are deficient in the diet, skeletal
muscle protein synthesis can be inhibited.3,4 This is very unlikely to be a problem for the typical bodybuilder as the condition would only manifest itself if he or she ate a diet that was predominately based on a certain food that was deficient in an amino acid over a few days, not meal to meal. Additionally, most bodybuilders consume a complete source of protein at almost every meal because any animal product will contain the complete spectrum of amino acids.
Even if one consumed an incomplete protein source at a meal there's no way a decrease in protein synthesis would occur so long as a complete protein source was consumed with this meal. One should therefore absolutely count incomplete protein sources toward their total protein intake since they're consuming the full spectrum of amino acids over the range of their entire diet.

Myth: "High-protein diets are hard on the kidneys."


Quite a few medical professionals have theorized that a high-protein diet may be hard on the kidneys since a highprotein diet increases the body's production of ammonia, which must be excreted by the kidneys as urea. As a result, lowprotein
diets have typically been recommended to people who suffer from renal disorders. However, the notion that a high-protein diet is hard on the kidneys in a healthy person is a big stretch. Researchers who recently conducted a review of the available scientific literature on the subject concluded that "no significant evidence exists for a detrimental effect of high protein intakes on kidney function in healthy persons." 5 Additionally, a study examining bodybuilders with protein intakes of 2.8 grams per kilogram vs. well-trained athletes with moderate protein intakes revealed no significant differences in kidney function between the groups.6 It's therefore reasonable to conclude that a high-protein diet is NOT hard on the kidneys.

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Myth: "Don't take your creatine with protein because protein contains glutamine and glutamine competes with creatine for
the same transporter!"





The Real Deal: There's not an ounce of truth to this. Creatine and glutamine have completely different receptors.
Creatine transport into skeletal muscle is regulated by the Creatine Transporter7 while glutamine transport into skeletal
muscle is regulated by a system known as "System Nm." 8 The only thing these transporters have in common is that
they are both sodium-dependent transporters, meaning that they use differences in sodium concentrations across the
cell membrane to drive creatine into cells. Apparently somewhere along the line, somebody believed that since glutamine
and creatine transporters both shared that characteristic, they must be the same transporter and the myth spread from
there. Let the confusion end here: they do not share the same transporter, and taking protein/glutamine with creatine
won't decrease creatine uptake into muscle.











Myth: "The more protein you take the better."





The real deal: There's little doubt that increasing one's protein intake is beneficial in achieving optimal anabolism, but
some people have taken "high protein" to the extreme. Protein intakes of 2 grams per pound and even 3 grams per
pound have been suggested by various trainers who believe that there's no upper limit to the anabolic effects of protein.
Unfortunately, the available scientific evidence doesn't agree with their views. As protein intake increases, the body
increases its production and activity of enzymes that break down and burn amino acids for energy.9,10 In fact, there's
some evidence that very high protein intakes may actually decrease protein synthesis when compared to more moderate
protein intakes.11 (Editor's Note: This study was conducted on endurance athletes, so it may not apply to strength-power
athletes - AM.) It appears from a review of the scientific literature that there's little anabolic benefit to protein intakes over
1gram per pound of bodyweight.12,13 While on a calorie-restricted diet, increasing protein intake may have additional
muscle-sparing benefits14 however, it may be wise to increase protein intake to 1.25-1.5 grams per pound of bodyweight.











Hopefully this article has helped clear up some confusion surrounding high protein diets. I fear the spread of misinformation
won't end however, so it's everyone's responsibility not to be so quick to believe everything they hear or read.
Keep in mind, if someone makes a claim they can't support with established scientific evidence, there's a good reason...
they likely have none.









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References:





- 1) Norton LE, Layman DK. Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise.
J Nutr, 2006 Feb;136(2):533S-537S.

- 2) Crozier SJ, Kimball SR, Emmert SW, Anthony JC, and Jefferson LS. Oral Leucine Administration Stimulates Protein
Synthesis in Rat Skeletal Muscle. J. Nutr, 135:376-382, March 2005

- 3) Barnes DM, Calvert CC, and Klasing KC. Methionine deficiency decreases protein accretion and synthesis but not
tRNA acylation in muscles of chicks. J Nutr, 1995 Oct;125(10):2623-30

- 4) Rivera-Ferre MG, Aguilera JF, and Nieto R. Muscle fractional protein synthesis is higher in Iberian than in Landrace
growing pigs fed adequate or lysine-deficient diets. J Nutr, 2005 Mar; 135(3):469-78.

- 5) Martin WF, Armstrong LE, and Rodriguez NR. Dietary protein intake and renal function. Nutr Metab (Lond), 2005
Sep 20;2:25.

- 6) Poortmans JR and Dellalieux O. Do regular high-protein diets have potential health risks on kidney function in
athletes? Int J Sports Nutr, 2000;10:28-38.

- 7) Snow RJ and Murphy RM. Creatine and the creatine transporter: a review. Mol Cell Biochem, 2001 Aug; 224(1-
2):169-81.

- 8) Hundal HS, Rennie MJ, and Watt PW. Characteristics of L-glutamine transport in perfused rat skeletal muscle. J
Physiol, 1987 Dec;393:283-305.

- 9) Block KP, Aftring RP, Mehard WB, and Buse MG. Modulation of rat skeletal muscle branched-chain alpha-keto acid
dehydrogenase in vivo. Effects of dietary protein and meal consumption. J Clin Invest, 1987 May;79(5):1349-58.

- 10) Boisjoyeux B, Chanez M, Azzout B, and Peret J. Comparison between starvation and consumption of a high
protein diet: plasma insulin and glucagon and hepatic activities of gluconeogenic enzymes during the first 24 hours.
Diabetes Metab, 1986 Feb;12(1):21-7.Bolster DR, Pikosky MA, Gaine PC, Martin W, Wolfe RR, Tipton KD, Maclean D,
Maresh CM, and Rodriguez NR. Dietary protein intake impacts human skeletal muscle protein fractional synthetic rates
after endurance exercise. Am J Physiol Endocrinol Metab, 2005 Oct;289(4):E678-83. Tipton KD, Wolfe RR. Protein and
amino acids for athletes. J Sports Sci, 2004 Jan;22(1):65-79.

- 11) Lemon PW. Effects of exercise on dietary protein requirements. Int J Sport Nutr, 1998 Dec;8(4):426-47.

- 12) Layman DK, Evans E, Baum JI, Seyler J, Erickson DJ, Boileau RA. Dietary protein and exercise have additive
effects on body composition during weight loss in adult women. J Nutr, 2005 Aug;135(8):1903-10.



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