Here's a summary of a few studies:http://www.jacn.org/cgi/content/full/19/suppl_5/513S
Most of the studies agree that athletes need increased protein amounts and that they should get 1.2 - 1.8g/kg of protein per day, depending on sport and training intensity.
If I choose the higher end (1.7) and mutliply my kilograms by that, I get that my diet should be about 25% protein.
It's a very controversial topic at this point; there isn't enough information out there to prove it one way or the other. Speaking of which, do you have any studies indicating increased protein intake is detrimental to athletes?
First, thanks for that study, I enjoyed it and learned many things. Sorry to sound arrogant but I found your study actually supports my postion (if eating enough calories, for fuel need, a 10% of calories as protein meets total protein needs.) . (Note: the higher end of the range you cited was shown for more cardiovascular leaning exercisers, versus body builders - For example, see Figure 1, of that study.)
Highlights, from your article, that are in agreement with my position:
1) The study states, "Although strength athletes can increase muscle growth with supplemental protein, this effect seems to attain a plateau at protein intakes (1.4 g/kg) far below intakes typical of experienced bodybuilders (Fig. 8 )."
It does add that creatine might increase that plateau but that is opinion not study findings.
So your study is indicating the same my study showed. 1.4 grams of protein per kilogram of body weight helps muscle gain but above that is marginal. My study showed .8 grams to 1.5 grams of protein per kilogram of body weight, so its upper range is above your study's. The 1.4 grams per kilograms equates to .65 grams per pound. My 10% protein and 3000 calories intake, gives me at least 75 grams of protein (and on workout days I get 110, as my calories are 50% more), which is close (workout days exceeds) what your study requirement would be. So a 10 to 12% protein, as total calories, and meeting your energy needs (total calories consume) will keep you in the range of both studies.
2) The report emphasizes carbohydrate intake for fuel. I am in total agreement with that. That is one of my arguments against increasing protein intake to the 20 to 30% range because to do that you are likely cutting back carbohydrates by the same amount caloric amount and robbing yourself of that more efficient fuel.
It reads: "Carbohydrate availability to exercising muscle is critical for intense muscle contraction, as it is a more efficient fuel (produces more adenosine triphosphate per unit of oxygen) than both fat and protein. In combination with the fact that the total carbohydrate stores in the body can be depleted in a single exercise bout, this makes carbohydrate the single most important exercise fuel. As a result, carbohydrate has been studied to a much greater extent than either protein or fat. However, inadequate carbohydrate for muscle contraction is also critical because its availability is inversely related to the rate of exercise protein catabolism (Fig. 2 ). Therefore, daily carbohydrate intake is of great significance for physically active individuals. Moreover, physically active individuals need to be much less concerned about excess dietary carbohydrate intake resulting in surplus body fat storage (and associated adverse health effects) compared to their sedentary counterparts because this substrate is used to replenish carbohydrates stores depleted by exercise training/competition sessions. In fact, rather than over-consuming carbohydrate, athletes typically have great difficulty replenishing carbohydrate stores following exercise."
3) As added commentary to 2) the article states: Fig. 2. Nitrogen excretion increases with prolonged, moderately intense exercise and especially so when carbohydrate stores are low. (Adapted from .)
That is in agreement with my position on carbohydrates. If you cut them below your fuel needs, your body is going to cannibalize its own muscle, after it depletes its carbohydrate stores. This hits on my idea that high protein intake might actually be detrimental to muscle development. What I project: You work out harder, you consume recent dietary carbohydrates then deplete your body's carbohydrate stores and then go into a mini ketosis burning your muscle for fuel.
Some added interesting points from the study you posted:
A) On overall energy needs, it states that body builders have the same requirements as the ones prescribed for sedentary people. See its Figure 1. It had weightlifters (I assume this means lighter weights, more repetitions) at 40% more, cross country skiers at almost double, From that trend, I assume it is stating that higher cardiovascular exercise demands more food intake than anaerobic ones (body building.)
B) The article states, Exercise Intensity, Duration and Type
Increasing exercise intensity and duration, at least with aerobic (endurance) exercise, causes increased use of protein, presumably as an auxiliary fuel [18–21]. Based primarily on nitrogen balance experiments, this results in an increased daily protein need of about 50% to 75% (1.2–1.4 vs. 0.8 g/kg) when compared to inactive individuals
I am in agreement with this. That is why high heart rate cardiovascular exercise is detrimental to muscle gain - runners, etc. are burning muscle. So body builders should watch their heart rates, when doing cardiovascular exercise and keep them fairly low (120-130 range), in comparison to runners hitting 150+. This might be concern for body builders engaging in HIT exercise.