增肌蛋白质的需要量？

jacky

Now let’s see what’s wrong with current guidelines for protein and why you need more protein than the reccomended guidelines. Why should you eat more protein than the recommended guidelines for muscle growth?Protein & Recommended Dietary Allowance (RDA): The RDA is defined as the “estimate of the minimum daily average dietary intake level that meets the nutrient requirements….” Though the term “recommended” clearly sounds like optimal, the RDA for protein is defined as the “minimum” amount of protein to prevent deficiency and not the optimal amount for health (.8 kg/bdy weight).
In fact, the recent Dietary Intake report (2005) recommends 10% -35% protein of daily energy intake for adults. Protein intake based on this 10-35% of energy levels is more than twice the current RDA of protein. Lately, there has been a growing consensus among nutritional experts that the current RDA of protein is clearly inadequate for optimum health & function.
For strength athletes, the RDA of protein is 1.2 -1.7 kg/bdy wt. Again these values are based on the “minimal” intake of protein required to attain nitrogen balance.  Nitrogen balance is used commonly to measure protein requirements.

Basically, a positive nitrogen balance means that you are in a state of anabolism or you are putting on some muscle. A negative nitrogen balance says that you are losing muscle. And if you are “in” nitrogen balance, it simply means you are neither losing nor gaining muscle(hope you didn’t miss the gaining part).
So eating protein based on RDA for strength athletes theoretically will only help you maintain the muscle you have.
Protein & Nitrogen Balance Method: Finding protein requirements with the nitrogen balances method have numerous limitations: It underestimates N losses from sweat, exhalation, the urea pool, and overestimates N intake. For example, nitrogen excretion from urine is used as an index of N excretion. But studies have shown excretion of N through sweat can go up by 150% with exercise.
So the studies might showing a greater protein balance might actually be lower since they are underestimating N loss & overestimating N intake.
As I mentioned earlier, the RDA recommendations are based on these nitrogen balance studies where the end point is nitrogen balance. In essence, these studies automatically assume that there is direct correlation between nitrogen balance and relevant physiological end points like strength & muscle growth. Ideally, muscle or strength should be the end point when protein requirement for athletes is determined.
So these N balance studies are not much reliable in estimating the optimal protein needs to put on muscle.
Protein & Muscle Mass Studies: Studies which did look at protein intake and muscle mass did show significant increase in strength and muscle with high protein whereas some did not. The researchers suspect the following reasons why some did not show an increase in muscle with high protein.

• The studies were of short duration and hence the small increments in muscle did not reach statistical significance and /or the existing muscle measurement techniques are not sensitive enough to record these minor changes.
• There are too many variables involved, like diet, sleep, work, training volume, fitness levels to determine the optimal protein intake for athletes from studies.
  

Protein & Health Concerns: There no evidence of high protein to cause any sort of health concerns in people with normal renal function. And since there are studies which did show increase in strength & muscle with high protein, it is better to be on the higher end of protein.
40% of calorie intake is considered the cut off since beyond these levels it gets harder to get adequate amounts of fat and carbs. 40 % for an 80 kg athlete will be 3.75 g/kg.  
Protein & Energy Intake: It has been shown that your total energy or calorie intake can have a greater influence on muscle mass than just your protein intake. Simply put, if you are not eating enough calories, it is quite impossible to be in positive nitrogen balance and gain or even maintain muscle even with sufficient protein. You might have to go for higher protein to be in a positve balance.
A number of studies have shown greater fat loss while maintaining muscle mass on a high protein diet compared to low protein diets. So that is yet another reason to stay on the high protein band wagon.
ConclusionLooking at all the above issues, the risk vs benefit, and the anecdotal evidences in favor of high protein, it makes no sense not to eat more protein than what the RDA reccommends for muscle growth.
My Protein recommendation for muscle growth & strength: 2.75 - 3.25 g/kg of body weight (1.25 - 1.50 gm/lb of bodyweight).
To gain serious muscle, hover around the lower end.
To maintain muscle or gain some muscle on a diet, stick to the higher end.


该贴已经同步到 jacky的微博

admin

俺也有蛋白粉

jacky

admin 发表于 2011-11-28 01:29
俺也有蛋白粉