Every few years we see a new study or media report which claims that “eating a high protein diet is bad for your kidneys!”
Understandably, this has a lot of fitness folks worried.
So let’s take a look into the decades of research on this topic and answer the big questions here; is there any truth to this, or are the media once again behaving like uneducated cock-toboggans?
Why Do People Believe This?
The link between protein and kidney damage dates all the way back to the 19870s, when scientists theorized that eating a lot of protein may “overload” the kidneys.
Considering that one of the main jobs of the kidneys is to break down the protein you eat and shuttle away any waste product (ammonia), if a high protein diet proved troublesome this could lead to some very serious health risks.
Concerns deepened when a 1988 study was published which claimed to have “found a direct link between high protein diets and kidney disfunction”. (1)
The researchers said that people who eat a high protein diet typically have a higher glomerular filtration rate (GFR). Now, your GFR is a health marker which is used for measuring the waste filtration levels of the kidneys, so they concluded that a diet which increased this marker must therefore be creating greater levels of stress for the kidneys.
That’s when this “high protein diets damage your kidneys” theory really went into over-drive.
It would’ve been great to have more research done on this topic at the time, but unfortunately it didn’t arrive until 2003. (2)
This time, researchers at Harvard Medical School discovered two very interesting things:
- People with pre-existing kidney damage (e.g. urea cycle disorder) do experience kidney issues when consuming a high protein diet.
- People with normal kidney function (e.g. 95% of the population) cope perfectly fine with a high protein diet.
“A high protein intake is not associated with renal function decline in women with normal renal function. However, it may accelerate renal function decline in women who already have renal insufficiency.”
– Dr. Eric Knight
Bring The Science
This was the first piece of academic data to really do a “deep dive” on the topic, but it certainly wasn’t the last.
Researchers from Belgium really went to town on this by having a group of trainees follow a classic “bodybuilding-style” diet where they ate a huge 1.3 grams of protein per pound of body weight (e.g. a 180lb guy would eat 234g protein/day), which is significantly higher than any other study, and once again the results showed that a high protein diet did not cause any issues at all for the kidneys. (3)
If we fast-forward a decade to 2016, a comprehensive 12-month study (by far the longest ever done on this topic) where trainees ate 1.1g protein per lb of body weight for six months and then increased it to 1.5g for the second six months once again confirmed that there were no negative side effects at all. (4)
And finally, a monstrous 2018 meta-analysis from McMaster University (famous for the discovery of HIIT!) trawled through every study ever done on high protein diets and possible kidney-related issues and confirmed that there is zero evidence to suggest that eating a high protein diet can lead to kidney problems. (5)
Case fucking closed.
“There’s no evidence to support the notion that a high protein diet will cause kidney damage in people who have normal functioning kidneys.
Unfortunately, that doesn’t stop people believing this myth. I recently spoke with a dietitian who had been spreading misinformation regarding this subject. When I asked them to provide scientific evidence to support their claims, they could not, but that just shows how far and wide this myth has been accepted – a DIETICIAN!”
– Mark Gilbert, B. Sc
Shame On You, Media!
We now know that our original 1970s theory about the effects of a high protein diets on the kidneys was dead wrong, but unfortunately that doesn’t stop the media from stirring up a controversy every few years.
Here’s where it really pisses me off.
You see, over the last decade I’ve seen several reports (link link link) where people have actually passed away as a result of suffering from undiagnosed kidney disfunctions, but the media have inconsiderately twisted their reports into clickbait headlines suggesting that whey protein shakes caused those deaths just to get more clicks.
What soulless bastards, huh?
“Sadly, the media and some ‘experts’ have misinformed the public that protein is dangerous for the kidneys.
Yes, if you have pre-existing kidney damage a high protein diet may be less than ideal for your body, but for the rest of us our kidneys were designed for that very function, and they do not become overburdened by it!”
– Dr. Jim Stoppani, PhD.
Russ’ Take-Home Advice
You’re perfectly safe.
The entire body of research on high protein diets and the kidneys shows us that we can process dietary protein and rid the body of unwanted waste product (ammonia) perfectly fine, and if this information ever changes you can rest assured I’ll change this article to show it.
However, if you’re unlucky enough to fall into the 0.1% of the world’s population who suffer from kidney problems such as UCD (urea cycle disorder) I recommend following the advice given in The 2017 Annual Review Of Nutrition and avoiding a high protein diet in order to reduce stress on your already weakened kidneys. (6)
Also, the vast majority of kidney disorders are identified at birth so you should already know if you’re suffering from a condition, however there are rare instances where people go undiagnosed all the way into adulthood, so if you feel like you might be suffering the effects from a possible kidney disfunction then I recommend going to see your GP about it ASAP.
References:
- Von Herrath, D., et al. Glomerular filtration rate in response to an acute protein load. Blood Purif (1988).
- Knight, E.L., 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).
- Poortmans, J.R., et al. Do regular high protein diets have potential health risks on kidney function in athletes?. Int J Sport Nutr Exerc Metab (2000).
- Antonio, J., et al. A High Protein Diet Has No Harmful Effects: A One-Year Crossover Study in Resistance-Trained Males. J Nutr Metab (2016).
- Devries M. C., et al. Changes in Kidney Function Do Not Differ between Healthy Adults Consuming Higher- Compared with Lower- or Normal-Protein Diets: A Systematic Review and Meta-Analysis. J Nutr (2018).
- Kamper A. L., et al. Long-Term Effects of High-Protein Diets on Renal Function. Annu Rev Nutr (2017).