"Too much protein is bad for kidneys."
We've all heard this one.
I've even heard that doctors promote this myth too.
But unfortunetly, the science behind this notion proves otherwise!
Let's take a look at the evidence.
IS TOO MUCH PROTEIN HARMFUL?
Previous research has found high protein diets increased what's known as glomerular filtration rate (GFR) (1).
GFR is an indication of waste filtration in the kidneys; so many people hypothesised that an increase in GFR must be a signal that the large amount of protein was putting the kidneys under too much pressure.
But as soon as a few people in the right places mention this; it gets accepted as fact!
But then years later, further research found that this wasn't the case (2).
Let's hear from the authors:
"High protein intake was not associated with renal function decline in women with normal renal function."
Further research (3) into bodybuilders found that a high protein intake wasn't detrimental:
"To conclude, it appears that protein intake under 2.8g.kg does not impair renal function in well-trained athletes as indicated by the measures of renal function used in this study."
This study was done on 83 overweight or obese people with type 2 diabetes.
They were split into 4 groups - the low protein group (19% protein), the high protein group (33% protein), a 19% protein intake with 3 days of resistance training a week, and 33% protein with the 3 days a week of lifting.
The group with the higher protein intake and 3 days of lifting, of course lost the most weight.
No surprises there.
But the big surprise was that NONE of the groups showed signs of kidney dysfunction.
And amazingly, there was no difference between the high protein diet and the control diet on the kidneys.
If you read these articles here on FIT'N'FLEXED frequently, you'll know all about the benefits of a high protein diet.
It seems that the benefits of a high protein diet seem to outweight any mythical negative effects of a high protein diet on the kidneys.
Obviously the high protein diet helps with body composition and is beneficial for health; so as far as I'm concerned, not undertaking a high protein diet for fear of something that's unfounded in the literature is quite silly!
So the evidence is pretty clear - stick to your high protein diet and enjoy the health and body composition benefits; knowing full well that it'll be safe for your kidneys!
"Stay Fit, Stay Flexed!"
REFERENCES
(1) Von Herrath D, Saupe J, Hirschberg R, Rottka H, Schaefer K. Glomerular filtration rate in response to an acute protein load. Blood Purif. 1988;6(4):264-8.
(2) Knight EL, Stampfer MJ, Hankinson SE, Spiegelman D, Curhan GC. The impact of protein intake on renal function decline in women with normal renal function or mild renal insufficiency. Ann Intern Med. 2003 Mar 18;138(6):460-7.
(3) Poortman JR, Dellalieux O. Do regular high protein diets have potential health risks on kidney function in athletes? Int J Sport Nutr Exerc Metab. 2000 Mar;10(1):28-38.
(4) Wycherley T et al. A High-Protein Diet With Resistance Exercise Training Improves Weight Loss and Body Composition in Overweight and Obese Patients With Type 2 Diabetes. Diabetes Care May 2010 vol. 33 no. 5 969-976.
Author
Dayne Hudson