According to interviews, many competitive bodybuilders take in massive amounts of protein. Some claim they have 600 grams a day or more. The goal is to maintain a positive nitrogen balance, since that promotes an anabolic effect in muscle. Studies conducted with recreational—that is, noncompetitive—persons, show that a range of 1.6 to 1.8 grams of protein per kilogram (2.2 pounds) is sufficient to maintain a positive nitrogen balance. That translates into a daily protein intake ranging from 144 to 162 grams for a 200-pound man—a far cry from the 600 grams suggested by some athletes.
The fate of the protein you eat is another matter of some contention. Many dietitians suggest that dire effects await those who get too much protein, including dehydration (protein metabolic waste products increase the need for water); a loss of vital minerals, such as calcium; kidney failure; and perhaps even a conversion of excess protein into bodyfat. Almost none of those side effects are known to occur with long-term athletic use, so they have little or no relevance to active people. The real-world fate of excess protein is oxidation in the liver, with eventual excretion of nitrogen waste product as urea through the kidneys. Normal kidneys have no problem handling this extra load, assuming the presence of sufficient fluids.
Besides its muscle-building effect, a high-protein diet is considered desirable for other reasons. Some studies suggest that protein intake influences the synthesis and secretion of various anabolic hormones, such as growth hormone and insulinlike growth factor 1, both of which are nothing more than long chains of amino acids strung together in a specific sequence. Eating extra protein, particularly at night before bed, is thought to offset the normal rise of the catabolic hormone cortisol, which peaks during the early-morning hours. Blunting cortisol release would tip the metabolic scales toward anabolism in muscle.
A problem with the often-quoted studies suggesting increased protein intake for hard-training athletes is that they involved subjects who were either untrained or recreational athletes. Neither of those groups, however, has much in common with competitive athletes, who as a rule are far more dedicated to their training and who often overtrain.
A recent study examined the true protein needs for competitive athletes.1 Twenty-three experienced college strength and power athletes, most of whom were football players, sprinters and throwers with at least two years of training experience. None had used any anabolic agents for six months before the study began. They engaged in a 12-week weight-training program, training four days a week on a split routine.
The subjects were divided into three groups, according to the amount of protein in their eating plan:
1) Ate less than the suggested amount of daily protein, 1.4 grams per kilogram of bodyweight. That’s still nearly twice the protein intake (0.8 grams per kilogram of bodyweight) suggested for most active people not engaged in exercise.
2) Ate the recommended protein intake, 1.6 to 1.8 grams per kilogram of bodyweight.
3) Ate more than the suggested protein requirement, above two grams per kilogram of bodyweight daily.
End-of-study metrics revealed no significant differences among the groups in body composition, lean mass or fat mass. While all three groups gained strength during the course of the study, those in the highest protein group gained 22 percent more strength in the one-rep-max squat and 42 percent more strength in the bench press than those in the recommended-protein-level group. Oddly, the researchers deemed those gains “nonsignificant.” They concluded that eating more protein than the suggested range of 1.6 to 1.8 grams per kilogram of bodyweight doesn’t yield significant results. They did, however, say that the results might have been different if more calories had been on the eating plan.
Protein has a direct relationship to calories; the fewer calories you take in, the greater your need for additional protein to ensure an anabolic response in muscle. Another aspect not considered in the study is that carbohydrates exert a protein-sparing effect that also bears a direct relationship to protein needs during training. In short, when you reduce carbs, you need to increase protein.
Another study also compared a high (1.9 grams per kilogram of bodyweight) to a normal (1.3 grams per kilogram of bodyweight) protein intake in 15 young men who trained with weights and aerobics for 90 minutes, three times a week.2 The lower figure represented 15 percent of the total daily calorie intake, the usual level of protein suggested for most active people.
Both protein diets lowered blood cholesterol levels, but only the higher intake led to a loss of bodyweight. No one experienced a change in body composition, but only the normal protein intake led to an enhanced arterial blood flow. Why that happened in the normal-protein group but not in the higher-protein group wasn’t explained; however, the authors suggested that a normal-protein diet promotes a dilation of blood vessels. That may have something to do with increased nitric oxide production in the lining of arteries. The direct precursor of nitric oxide synthesis is the amino acid arginine. A smaller intake of arginine due to lower protein intake may let more arginine into the blood. Large amounts of oral arginine are known to be mostly degraded by a liver enzyme.
References
2 Ferrara, L.A., et al. (2006). Effects of different dietary protein intakes on body composition and vascular reactivity. Eur J Clin Nutr. 60(5):643-649
©,2013 Jerry Brainum. Any reprinting in any type of media, including electronic and foreign is expressly prohibited.
