No disrespect meant NJ, because this IS a controversial subject. but did YOU read those articles?? The first one was referring to people that ALREADY had kidney failure, and the second one clearly states that there are DOZENS of reasons why your creatinine might be elevated (including dehydration).
To date there is no published evidence that a high protein diet produces any negative effect on metabolism in bodybuilders or any other type of athletes.
Recently, a comprehensive study completed by Jacques Poortmans and Oliver Dellalieux (published in Int. J. Sport Nutr. & Exerc. Metab. 11;28-35:2001) at the University of Brussels in Belgium investigated this aspect directly.
These scientists assessed whether high protein diets affect the health and kidney function of bodybuilders and other athletes. Their study involved 20 bodybuilders and 18 other highly trained athletes that consumed a high protein diet. (Approximately 2 grams of protein per kilogram of body weight per day. More than double the recommended daily allowance.)
Their diets were analyzed to provide total calorie, protein, fat, carbohydrate, and calcium intake each day. Blood and urine samples were taken from the athletes and spectrum of analyses were performed looking at glomerular filtration rate (creatinine clearance), potential change in glomerular membrane permeability (albumin excretion rate), urea and uric acid clearance, nitrogen and calcium balances and any modification in kidney free water balance.
In addition to the resting condition, the researchers also wanted to obtain other data that would be important to hard training athletes. Very intense exercise temporarily impairs kidney function (a natural, safe, and regular process). However, the research wanted to see if a high protein diet would produce a detrimental impact on this physiological aspect. So analyses were performed before and directly after a bout of very intense (cycling) exercise.
Some of the athlete's in the study were documented to have protein intakes as high as 2.8 grams per kilogram of body weight per day. However, when the results came in, the high protein athletes showed no fundamental differences that could be associated with damage or impaired kidney function in any way.
These athletes did show higher values for creatinine and uric acid clearance, However, all readings fell within the upper limit of normal levels. Despite the high protein intake there was no accumulation of urea, demonstrating no toxicity. Glomerular filtration rates were normal and there were no signs of even moderate hyperfiltration. This aspect is important.
Hyperfiltration seems to precede the excess excretion of protein plasma into the urine. It is an indicator of the amount of "stress" on the kidneys. The albumin clearance rates also supported the observation that a high protein diet does not stress healthy kidneys. In fact, all readings taken from these athletes proved absolutely normal. Their kidney function was in no way effected by a high protein diet.
The combination of high protein intake and intense exercise didn't appear to impair any aspect of kidney function either. The reduction of several clearance rates as a result of the intense exercise were in line with other reported observations in exercising humans.
Nutritionists often site high protein diets to cause of excessive calcium loss. However, all calcium excretion rates fell within normal ranges. This was despite the bodybuilders taking in higher amounts of calcium in their diets! The bodybuilders absorbed more calcium from their diets! The researchers suggested one reason for this may be that bodybuilding places a higher load on the musculoskeletal system and therefore bodybuilders require more calcium.
There was no difference between the bodybuilder's and the other athlete's calcium excretion levels.
The medical community uses protein ingestion as a key determinant of kidney function and a marker of kidney "health". High protein diets do produce high amounts of urea, an end product of protein metabolism that is excreted in urine. Because of their physical activity, athletes are at risk of dehydration. Severe dehydration limits urea excretion, so theoretically, high protein diets may place stress on the liver (to oxidize excessive protein) and on the kidneys (causing glomerulonephritis-a mechanism of hypertension).
Research has shown that low protein diets reduce the progression of renal failure in patients with kidney disease. For these two aspects, (but no scientific evidence) high protein diets have earned an undeservedly bad reputation within the medical community.
The scientists responsible for this research concluded that high protein intakes of 170 to 243% of the RDA show no toxicity, dehydration, calcium loss or impairment of kidney function. Also, the researchers cautioned that some of the upper-end clearance ranges of some clinical markers witnessed in this study are not solely related to a high protein diet as many other individual differences play a big part in this regard.
The researchers concluded and recommended that high protein diets should not be used as an "escape goat" to explain these variations.
But one thing I wholeheartdly agree on.....the vast majority of bodybuilders eat FAR more protein than they need. And as I said before, no one knows the consequences of eating higher protein over a long period (decades or lifetimes) in humans. To reiterate what has been covered before, 1.2-1.8 grams protein per kg bodyweight is plenty. Also, some proteins (such as soy) can improve kidney function.
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