Have you ever had this conversation?
You: “I’m going to start eating healthier. Lots of protein, vegetables, and no junk food…”
Friend: “I wouldn’t do that… I’ve heard protein is bad for your kidneys.”
You: “F**k. What’s the point in even trying?”
If so, you’re not alone. Confusion is king in the nutrition industry, and today I’m going to tackle one of the biggest beliefs out there to give you a definitive answer: is a high protein diet bad for your kidneys?
Strap in, and get ready to make some self-appointed experts at your workplace rather unhappy…
Does Protein Damage Your Kidneys?
In a nutshell; no.
The theory behind protein being bad for the kidneys stems back to a 1988 study.
In this trial, researchers discovered that increasing the protein intake of subjects resulted in a higher glomerular filtration rate. This is used as a marker for waste filtration in the kidneys.
It was believed that this showed our kidneys were placed under more stress when our diet is high in protein. (1)
However, this theory has been debunked via more recent research.
A 2003 study from Harvard Medical School found that no additional stress was placed on the kidneys due to directly increasing protein consumption, nor did it raise glomerular filtration rate.
The kicker here is that all of the test subjects had normal renal function.
The researchers found that increased protein intake did have some negative side effects in a sub-group of participants who had mild renal insufficiency. (2)
“High protein intake was not associated with renal function decline in women with normal renal function.
However, high protein intake (particularly animal protein) may accelerate renal function decline in women with mild renal insufficiency.”– Eric L. Knight, head researcher
Basically, unless you have pre-existing kidney issues, you have nothing to worry about.
Another study, this time published in the International Journal of Sport Nutrition and Exercise Metabolism, looked at the effects of a high protein diet on the kidneys of bodybuilders and athletes.
For the folks who read my website, that’s a dream scenario to answer this question!
This time around, they tested participants with protein intakes of up to 1.3 per lb of body weight (224g protein per day for someone weighing 176lbs). which is right in the sweet spot for maximum muscle growth.
Once again, it had no effect on renal function in any of the athletes involved. (3)
As recently as 2016, a study published in the Journal of Nutrition and Metabolism laid this issue to rest.
With a study group consisting of well-trained men, each participant followed their regular diet for a period of six months, followed by a six month period of a high protein diet. This gave the researchers a baseline to work with, and provided an entire year of results.
The findings were interesting.
During the six months on their regular diet, the men consumed around 1.1g per lb of body weight (200g protein for someone weighing 176lbs). For the high protein phase this increased to a whopping 1.5g per lb of body weight (265g for someon weighing 176lbs).
Conclusion? You guessed it, no negative side effects or kidney issues. (4)
Take Home Points
Despite the popularity of this belief, it is a myth.
Any studies which point to a link between kidney issues and high protein diets make it clear that participants had pre-existing kidney disease or other kidney disorders.
Unfortunately, the media will continue to run wild with bulls**t myths all day long, so I advise people to listen to the researchers themselves.
Here’s what nutrition expert Mark Gilbert had to say:
“There’s no evidence to support the notion that a high protein diet will cause kidney damage, but that doesn’t stop this myth from being incredibly popular!
In fact, I recently had an email conversation with a dietitian who insisted increased protein intake would cause kidney damage – a dietitian!
When I asked her to support her claim with scientific facts, she could not provide any evidence whatsoever.”– Mark Gilbert, B. Sc
Dr. Jim Stoppani follows a high protein diet for most of the year, and he backs this up:
“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 don’t become overburdened by it!”– Dr. Jim Stoppani, senior science editor at Muscle & Fitness magazine
So there you have it!
As always, if any research comes to light in future which changes this information, the article will be updated immediately.
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- 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)