Does a High Protein Diet Harm the Kidneys?
We all know we need protein to build and maintain muscle. Although, whenever a high-protein diet is brought up, there’s likely someone around who will jump to make the claim that it’s bad for your kidneys.
Well, are they right? I would argue no. In this article, I aim to breakdown what the research actually says regarding protein intake and kidney health in otherwise healthy individuals
Disclaimer: This is not medical advice, simply a breakdown of what the research says so you don’t have to read the studies yourself. If you have unique concerns over your own personal situation, please seek the counsel of a registered dietician or your primary care physician.
Why people make this claim:
First, some claim that a ‘wear-and-tear’ sort of mechanism is taking place.
One of the kidney’s roles is to deal with nitrogen throughout the body, and amino acids (the individual constituents of protein chains) carry a nitrogen group.
This leads people to make the claim that this makes the kidneys ‘work too hard’ which will lead them into failure states.
Others note that people who have higher protein intakes tend to have higher glomerular filtration rates.
The kidneys can, in some ways, be seen as the filters of the body.
Your glomerular filtration rate can simply be seen as the amount of filtrate being filtered by the kidneys.
This leads people to make the quick jump to assuming that high protein intakes are damaging the kidneys.
Both of these claims are simply hypotheses made by people across mainstream and social media.
When you begin to look at the available long-term outcome data in humans, a different picture is painted.
let’s discuss:
What does the research say on protein intake & kidney health?
A systematic review & meta-analysis by Devries et al. looked at 40 different randomized control trials in humans.
A systematic review basically means a “study of studies.”
A meta-analysis is an advanced statistical method of pooling data from multiple, single studies into one conclusion
They looked at protein intakes ranging from 0.42 g/kg/day to 2.4 g/kg/day.
“g/kg/day” refers to grams of protein per kilogram body mass per day. If you weigh yourself in pounds, divide your bodyweight by 2.2 to convert it to kilograms. Then you can use this doses to see what these intakes would look like for you.
For reference, the RDA for protein is 0.8 g/kg/day.
They found that although people who habitually had higher protein intakes had higher glomerular filtration rates, there was no change in glomerular filtration rate when a person increased their intake from low- to high-protein.
The authors’ ultimate conclusion was that high protein diets have a “nonexistent or trivial effect” on overall kidney health.
One reason that might explain the higher glomerular filtration rate in people with higher habitual protein intake is their muscle mass.
Bottom line: this systematic review & meta-analysis provides evidence that high protein intakes (up to 2.4g/kg/day) do not harm the kidneys.
This umbrella review from the German Nutrition Society looked at 6 systematic reviews with meta-analysis & 3 systematic reviews without meta-analysis in humans.
The intake of protein ranged from 1.0 g/kg/day all the way up to 3.3 g/kg/day.
They found the blood markers such as creatinine might be elevated but that this isn’t indicative of kidney damage.
Again, the elevation of blood markers such as creatinine is more probably due to increased muscle mass, which isn’t cause for concern.
Bottom line: this umbrella review of systematic reviews provides evidence that high protein intakes (up to 3.3 g/kg/day) do not harm the kidneys.
All-in-all, the research seems abundantly clear that high protein intakes do not cause or accelerate the progression of chronic kidney disease in individuals who do not have chronic kidney disease.
Protein restriction is historically a common recommendation made to people with pre-existing chronic kidney disease, however, even this has come under scrutiny as new medications have emerged which make any benefit achieved from protein restriction trivial. [source]
The case FOR higher protein intakes
If you came across this article, I assume it is because you are concerned with the safety of a high protein intake.
Hopefully, I have provided enough evidence to convince you that there is no cause for concern in regard to high protein intakes and kidney health.
In fact, when you look at protein intake in relation to many other health markers there seems to be. no cause for conern.
On the contrary, maintaining a high protein intake throughout your lifespan is likely far more health-promoting than a low- or moderate protein intake because it creates an optimal environment for muscle health, growth, and function.
For instance, higher protein intakes have been shown to:
Aid in weight loss & weight management [source]
Reduce risk of various chronic diseases such as diabetes or cardiovascular disease (only when paired with strength training) [source 1] [source 2]
Reduce risk of sarcopenia & help to maintain physical independence throughout the lifespan (only when paired with strength training [source]
To go into more detail on why higher protein intakes are beneficial would require its own article.
Nonetheless, the overarching point is this: there’s no reason to fear a high protein intake and many well-documented reasons to strive for one.