From a thread here on IM...
My favorite study, although not recent, was reported in the highly respected American Journal of Clinical Nutrition (28:29-35; 1975). It involved men performing “heavy physical activity,” including isometric exercises, treadmill sessions, stationary bike riding and other “sports activities,” during a 40-day period. One group took in 100 grams of protein per day; the other, 197 grams. The calories were the same for both groups.
What were the results? The researchers reported that the additional protein “did not enhance physical performance.” That means the men who ate the higher-protein diet didn’t walk longer on the treadmill, ride further on the bike or apply more pressure on the isometric exercises. The study concluded that consuming additional protein failed to improve sports performance and so was “unnecessary.” Nevertheless, it did have an interesting “side effect.” The researchers went on to report that the men who ate the high-protein diet did “increase body protein stores and muscle mass.”
Oops! I guess the sports nutrition author forgot to mention that while extra protein won’t help those young men she counsels lift heavier weights or enable them to train longer, it will let them build bigger muscles. (Of course, the irony is, that’s why they come to her in the first place—they want bigger muscles.) That’s what success means to bodybuilders—more muscle mass. The guy with 20-inch arms couldn’t care less about the guy who can curl 20 more pounds than he can but has arms that are only 17 inches. That’s the reason bodybuilders never win the World’s Strongest Man Competition, though they often place higher than most other sports superstars. The winners are usually the guys with big muscles and big bellies—in other words, the strength athletes. If your goal is simply to be stronger, then use low repetitions and heavy weights and eat like a horse, without worrying about muscle size and symmetry. If your primary goal is bigger muscles without excess fat (you’ll also increase your strength to a significant degree), then the literature clearly states that you do need to increase protein intake. In the study cited above, the group that gained more muscle mass ate twice as much protein as the control group. They didn’t do it just by eating more food. In order to reach the high protein intake without unnecessary fat and sugar, they used Casec (a milk protein isolate—not powdered milk) and Meritene, an early protein supplement that was often used in hospitals. A more recent study that was reported in the International Journal of Sports Nutrition (1:127-145; 1991) came to a very different conclusion than the 1975 study: “Present data indicate that strength athletes should consume 1.5 to 2.0 grams of protein per kilogram of bodyweight per day, which is 188 to 250 percent of the RDA for protein.” The idea that bodybuilders need more protein is backed up by numerous other studies. •As reported in the Journal of Sports Medicine (8:161; 1989), “Weightlifting training can also lead to a daily protein requirement that exceeds the current RDA.” •In the journal Metabolism (12:259-274; 1970) the authors of another study found that 2.0 to 2.2 grams of protein per kilogram of bodyweight per day was “barely sufficient to maintain nitrogen balance during moderate-intensity strength training.” Their conclusion was that a weightlifter’s protein requirement “increased proportionally to training intensity.” •An article titled “Maximizing Performance With Nutrition,” published in Medicine and Science in Sports and Exercise (19, July ’97), reported that “the protein RDA may be 10 to 100 percent higher for individuals who exercise on a regular basis. Optimal intakes, although unknown, may be even higher, especially for individuals attempting to increase muscle mass and strength.” In reviewing a number of studies, the author stated that “these studies indicate that the current protein RDA is insufficient for both strength and endurance athletes, and several suggest that the actual requirement is considerably higher.”
A positive nitrogen balance indicates that the body is taking in more protein (nitrogen) than it excretes. You must have a positive nitrogen balance before muscle growth can begin, as your body builds the new muscle with the extra. There’s some speculation that as positive nitrogen balance increases, so do muscle size and strength. The last article suggested that “perhaps, by maintaining a more positive nitrogen balance, protein synthesis would be further enhanced, leading to larger and stronger muscles.” It pointed to a study that involved elite Romanian weightlifters who increased muscle mass by 6 percent and strength by 5 percent when their protein intake was increased from 225 percent of the RDA to 438 percent.
Why have the study results differed so much about the amount of protein necessary for muscle growth? According to the authors of that last article, “Exercise intensity appears critical and may explain why some studies have not observed an increased protein requirement.”
As for the frequently mentioned health hazards—including the claim that excess protein can cause liver or kidney damage: “Actually, except in preexisting liver or kidney abnormalities, there is little documented evidence of health problems due to a high protein intake.… In an active individual the fate of ingested protein is likely quite different than in a sedentary individual.”
So the scientific literature doesn’t clearly state that bodybuilders don’t need additional protein to build muscle mass. In fact, it clearly states the opposite—that bodybuilders looking to increase muscle size need significantly more protein than nonbodybuilders.
To tell people to simply eat more at meals is very ambiguous. They may eat more fats and carbohydrates, in which case their muscles won’t grow but their waists certainly will. Remember that in the first study cited above, both groups of subjects ate the same calories but one got double the protein with that calorie level, and they were the ones who gained mass.
The bottom line is that bodybuilders need more protein, and supplements like protein powders do help. You also want to be leery of so-called nutrition experts who aren’t familiar with bodybuilding and think that performance in bodybuilding equates to performance in other sports. In bodybuilding, performance means big, symmetrical muscles—and for that very reason bodybuilding nutrition is a different animal from nutrition for other sports.