Can eating too much protein be bad for you?
Answered under the premise that protein shakes are a direct protein supplement to diet, ignoring their detailed composition and basing answer on the above title. As with ALL supplements, read and understand the ingredients list and what makes those ingredients up. Look for full disclosure of ingredients on the labels and you can always check most supplements on labdoor.com.
Click the next link for a comprehensive answer tailored to Whey Protein
When looking at active male athletes and measuring urinary creatinine, albumin, and urea no significant changes were seen in protein dosage ranges of 1.28-2.8g/kg bodyweight.2 The aforementioned study lasted 7 days, but survey research supports this lack of association (in post-menopausal women). 2
Too much, too fast
There do appear to be functional changes in the kidneys related to protein intake . As protein does modulate renal function, these interactions may lead to damage if imposed acutely onto mice (from 10-15% of the diet, up to 35-45% of the diet immediately) and one study in healthy humans going from 1.2g/kg to 2.4g/kg (doubling) was associated with higher than normal blood values of protein metabolites; a trend was noted for adaptation (increasing GFR) but it was not enough to clear uric acid and BUN over 7 days.
These studies are likely indicative of a 'too much, too fast' situation, as controlled changes do not lead to adverse changes in kidney function. Thus, it would be prudent to slowly change protein intake over a moderate length of time.
Damaged or unhealthy kidneys
Restricted protein diets are recommended for those with kidney damage, as it slows the seemingly inevitable progression of kidney damage. If protein was not controlled for in those with renal damage, it would accelerate (or at least not reduce) the decline in function.
The role of the Kidneys
Kidneys can acutely increase the Glomerular filtration rate (GFR), or the rate of filtration of the blood. They do this in response to dietary protein intake, and the lack of this compensation in some forms of kidney damage are a reason protein intake is controlled for in kidney disease management.
Additionally, the kidneys serve to regulate acid-base balance in the body via the sodium-bicarbonate buffering system. Disorders in acid:base balance can further pathophysiology (symptoms and signs of the disease) of renal complications.
These protective measures appear to be preserved in healthy kidneys, but begin to fail when they kidneys are otherwise damaged.
Don't worry about it if you have healthy kidneys and control your
protein intake if you have damaged kidneys. It may be prudent to
gradually increase protein intake to higher levels rather than jumping
in both feet at a time, but there isn't much on this topic.
It is generally recommended to consume more water during periods when
protein intake is being increased. Whether or not this has biological
basis is not known, but it may be prudent to do
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- Beasley JM, et al Higher biomarker-calibrated protein intake is not associated with impaired renal function in postmenopausal women . J Nutr. (2011)
- Knight EL, et al The impact of protein intake on renal function decline in women with normal renal function or mild renal insufficiency . Ann Intern Med. (2003)
- Brändle E, Sieberth HG, Hautmann RE Effect of chronic dietary protein intake on the renal function in healthy subjects . Eur J Clin Nutr. (1996)
- King AJ, Levey AS Dietary protein and renal function . J Am Soc Nephrol. (1993)
- Dietary protein intake and renal function
- Wakefield AP, et al A diet with 35% of energy from protein leads to kidney damage in female Sprague-Dawley rats . Br J Nutr. (2011)
- Aparicio VA, et al Effects of high-whey-protein intake and resistance training on renal, bone and metabolic parameters in rats . Br J Nutr. (2011)
- Frank H, et al Effect of short-term high-protein compared with normal-protein diets on renal hemodynamics and associated variables in healthy young men . Am J Clin Nutr. (2009)
- Wiegmann TB, et al Controlled changes in chronic dietary protein intake do not change glomerular filtration rate . Am J Kidney Dis. (1990)
- Levey AS, et al Effects of dietary protein restriction on the progression of advanced renal disease in the Modification of Diet in Renal Disease Study . Am J Kidney Dis. (1996)
- [No authors listed Effects of dietary protein restriction on the progression of moderate renal disease in the Modification of Diet in Renal Disease Study . J Am Soc Nephrol. (1996)
- von Herrath D, et al Glomerular filtration rate in response to an acute protein load . Blood Purif. (1988)
- Bosch JP, et al Renal functional reserve in humans. Effect of protein intake on glomerular filtration rate . Am J Med. (1983)
- Skelton LA, Boron WF, Zhou Y Acid-base transport by the renal proximal tubule . J Nephrol. (2010)
- Yaqoob MM Acidosis and progression of chronic kidney disease . Curr Opin Nephrol Hypertens. (2010)
- Kraut JA, Madias NE Consequences and therapy of the metabolic acidosis of chronic kidney disease . Pediatr Nephrol. (2011)