Written by Layne Norton
25 September 2006


Bodybuilding's Biggest Protein Myths DEBUNKED!


            Bodybuilding, more so than any other sport, seems to have developed many myths that people cling to so strongly that they're accepted as FACT even though there may be little or no scientific evidence supporting these myths. Protein might possibly have more ill-founded myths surrounding it than any other subject, probably because it plays such a large role in any 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

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 high-protein diet increases the body's production of ammonia, which must be excreted by the kidneys as urea. As a result, low-protein 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.


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 mis-information 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.



  • 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.