Kidney Concerns?

But isn’t keto hard on your kidneys?

This topic comes up time and time again, so why not dedicate an entire page to it? Many people are worried about starting a ketogenic diet due to fear of it being hard on the kidneys. At the time of this writing, the first thing that pops up in Google when searching for “ketone effects on kidneys” is this: Ketosis & Kidney Failure.[1] It is an article by and goes through talking about all the dangers of a ketogenic diet for the kidneys. Check out a snapshot of the article below:


People claim the ketogenic diet is hard on kidneys

Ouch… This sounds pretty scary, right? So we must address the issue! Let’s get to the bottom of this in true scientific fashion. Rather than starting with an idea and trying to prove it correct, let’s start from a place of ignorance and true longing for understanding.

We do not blame anybody for being concerned about their kidneys. It is a legitimate question. However, after doing some reading on the subject, you will find there is nothing to be afraid of. As usual, let’s start with some basic physiology of the kidney. When we understand that, we can understand the different effects a ketogenic diet will have.

What does it do in our bodies and what is necessary for proper function?

Kidney Physiology & Function

The kidney is a vastly complex organ. Entire books have been written about this subject alone, so let’s take an overarching view of it. The kidneys’ main function is filtration. They excrete metabolic waste products and also control solute concentrations in the blood.[2] The solute concentration function includes regulating things like water, mineral solutes (sodium, calcium, potassium, and magnesium), and acid / base content. It helps make sure there is a balance with the acidity of the blood to make sure that it does not get too acidic or basic.

Blood will pass through a part of the kidney called the glomerulus, and it will filter out some of the waste products our bodies don’t need. Do you know where this waste goes? Yep, it goes right through the rest of the urinary tract. After the waste products are filtered through from the kidneys, they pass along down tubes called ureters and lead right to the bladder.[3] As you may know, this urine is how we get rid of the waste products of our body.

The kidneys will pull things from blood, and then it will give some of that stuff back later down the line (if it is needed and the concentrations are too low). It does this not just with waste products, but also with small proteins. Usually the kidneys will give them back after filtration. It is a very intricate process with many steps and tubes involved. Check out the diagram below of one nephron (functioning section) of the kidney.[4


Anatomy of the kidney - the ultimate filtration system


Ketone effects on kidneys

There are 1 million of these sections in each kidney! Wow, that is a lot. Needless to say, your kidneys process and filter a lot of blood. But let’s get back on topic and how this relates to ketosis. When you generate ketone bodies in your liver, and they pass through the blood, they get filtered by the kidneys – just like everything else. That is why you can test your level of ketosis using urine strips. They test the ketone content of your pee and use that to estimate your body’s level of ketosis.

The point here is that there are natural systems in place for your kidney to filter ketones. There is little research on this topic specifically, but there is absolutely no research that your kidneys are damaged by ketone bodies in nutritional ketosis. It doesn’t make sense. Kidneys filter out excess ketones if there is a high concentration gradient. This is yet another mechanism by which your body regulates blood acidity. Your blood will not become acidic on a ketogenic diet. It will only become acidic in the complete absence of insulin (type 1 diabetes).

Okay, so there is no research that kidneys cannot handle ketones. They are also not damaging to the kidneys in any way when done through nutritional ketosis. So what’s the big problem then? Why are so many people concerned about the diet on renal function?


Problems with protein

This is the biggest concern people have with kidney function. They are afraid large amounts of protein will damage the kidneys. Again, these are valid concerns – especially for the average person who does not study physiology for fun. We offer to show you an opposing side to this argument.

Ketogenic diets are not high protein

First of all, who the heck said a ketogenic diet is high in protein? NO ONE… EVER (except those who spread unwarranted fear of keto). The diet is moderate to low in protein with it making up about 20-25% of total caloric intake (or less).[5] That is quite reasonable, and no one could ever suggest that is “high.” But let’s look at what that same article had to say about that…


People claim keto is high protein. Huh??

Where do these people get off!?

It is so obvious they didn’t even try to research a ketogenic diet. These kinds of people are so bent out of shape because they are scared of change. They walk around claiming the dangers of ketosis, and it is absolutely ridiculous. Everyone knows high protein content will kick you out of ketosis. Therefore, by definition, you are no longer on a ketogenic diet when eating lots of protein.

They have no scientific research to back up any claims. Where are their sources of information? Oh… They don’t have any. They just want to shout how bad a high fat diet is at the top of their lungs. Why? Who knows – but this is clear evidence of the lack of scientific confirmation when it comes to the “opposing side.” They base recommendations on emotions – not scientific proof.

High protein can be damaging with pre-existing kidney problems

So we just mentioned a ketogenic diet is not high in protein. However, if someone is following a poorly formulated “ketogenic diet” (high in protein), they still will have no problems. On normal functioning kidneys, high amounts of protein have no effect.[6] Now if the kidneys are dysfunctional or have reduced mass, then high protein may be harmful.

High protein is only bad for those with pre-existing kidney dysfunction

Reducing the protein content in the diet of mice with reduced renal mass showed a decline in degradation.[7][8] This suggests that having high amounts of protein may worsen the degradation of the kidneys – again, only for those with pre-existing problems. Those with worsened conditions were fed a diet of 40% protein.[8] To repeat the point from above, no one on a ketogenic diet should be eating that much protein anyway.


There is nothing to be afraid of. Simply be mindful. If you already have kidney damage or disease, then you need to watch how much protein you are taking in. But guess what… You need to watch your protein intake no matter what diet you are on! This is not specific to the ketogenic diet. So why all the hate for keto?…

Unfortunately, there is no exact amount of protein that we can tell you is okay to take. A ketogenic diet level of protein (~ 20%) works for most people. Just be sure to work with your doctor and do your regular check-ups for your kidney function.

What really harms the kidneys?

Although normal amounts of protein won’t harm kidneys, something else will: high blood sugar. That is the real fear we should have. Having high amounts of sugar in your diet leads to high blood sugars, and those high blood sugars (glucose) generate more advanced glycation end-products (AGEs). These AGEs tend to bind to proteins and other molecules and end up ruining their functionality.[9][10] This causes tons of problems in the body, and that is why diabetes leads to so many problems.

Do you know what is one of those common problems diabetics usually have? Nephropathy. Yep, that is kidney disease. These AGEs make their way into the kidneys and cause significant damage (glomerular sclerosis), especially in diabetic subjects.[9] Also, other studies show that high dietary sugar will lead directly to renal damage.[11]

Here is how it’s believed to happen:

  • High dietary sugar causes high blood sugar.
  • High blood sugar creates an excess of AGEs.
  • These AGEs are filtered out through the kidney but end up sticking there and damaging it (causing sclerosis and inflammation).

Avoid sugar if you want better kidneys

It makes such logical sense. Does anything like that happen with fat? NOPE. People are worried about the wrong things. If you had the choice, would you rather be on a high carbohydrate diet where these AGEs are prevalent and cause long-term damage?

Fructose is also a major problem

Fructose is pretty awful stuff – especially in the amounts we consume it in today’s world. Some people even consider it much worse than glucose. They are both sugars, but fructose has more direct and adverse effects. It is inflammatory and causes a lot of oxidative stress at the same time as increasing visceral fat (the bad kind of fat around the organs).[12][13][14] Do you think that has an effect on the kidneys?

Whatever you do, please reduce the amount of fructose in your diet. It does us no good. While it has many adverse effects on the body as a whole, it will also lead to kidney disease alongside the inflammation and hypertension.[15] It is no joke!

A high fat diet is the answer

Clearly there is plenty of scientific evidence that high dietary and blood sugars are the real concern. Avoid them to the best of your ability. That includes avoiding high intakes of carbohydrates because they, too, turn into sugar in the blood – especially if you are diabetic. So what do we replace those calories with then? Yes, fat! There is no evidence that a high fat diet does any harm on kidneys, so wouldn’t this be logical diet for those fearful of kidney disease?

With all of the wonderful things that come about with a ketogenic diet, why wouldn’t you go for it? The kidney debate is a distraction. The science is there that your kidney will be more than fine. Enjoy a full life with a ketogenic diet and don’t worry about these minor things haters like to bring up.

Eat more fat and gain better kidney function. If there are people concerned about a ketogenic diet being harmful on kidney function, we would argue use of the diet for your kidneys. The reduction of AGEs and inflammation will do wonders for your kidney. Just be sure to keep protein intake to a moderately low amount if you have pre-existing kidney problems.


[1] Ogunjimi A.  “Ketosis & Kidney Failure”. (2017). [Online]. Available: Accessed: 5 June 2018.

[2] “The Kidneys”. Basicmedical Key. [Online]. Available: Accessed: 5 June 2018.

[3] The Urinary Tract & How It Works”. National Institute of Diabetes and Digestive and Kidney Diseases. [Online]. Available: Accessed: 5 June 2018.

[4] “Overview of Renal Function”. University of Utah (Bioengineering 6000 CV Physiology). [Online]. Available: Accessed: 5 June 2018.

[5] Sullivan PG, Rippy NA, Dorenbos K, Concepcion RC, Agarwal AK, Rho JM. (2004). The ketogenic diet increases mitochondrial uncoupling protein levels and activity. Annals of Neurology 55: 576-580.

[6] Skov AR, Toubro S, Bulow J, Krabbe K, Parving HH, Astrup P. (1999). Changes in renal function during weight loss induced by high vs low-protein low-fat diets in overweight subjects. International Journal of Obesity and Related Metabolic Disorders 23(11): 1170-1177.

[7] Klahr S, Levey AS, Beck GJ, Caggiula AW, Hunsicker L, Kusek JW, Striker G. (1994). The Effects of Dietary Protein Restriction and Blood-Pressure Control on the Progression of Chronic Renal Disease. The New England Journal of Medicine 330(13): 877-884.

[8] Hostetter TH, Meyer TM, Rennke HG, Brenner BM, Noddin JA, Sandstrom DJ. (1986). Chronic effects of dietary protein in the rat with intact and reduced renal mass. Kidney International 30(4): 509-517.

[9] Singh R, Barden A, Mori TA, Beilin LJ. (2001). Advanced glycation end-products: A review. Diabetologia 44(2): 129-146. 

[10] Goldin A, Beckman JA, Schmidt AM, Creager MA. (2006). Advanced Glycation End Products: Sparking the Development of Diabetic Vascular InjuryCirculation 114(6): 597-605.

[11] Yudkin J, Kang SS, Bruckdorfer KR. (1980). Effects of high dietary sugar. British Medical Journal 281(6252): 1396.

[12] Cigliano L, Spagnuolo MS, Crescenzo R, Cancelliere R, Iannotta L, Massoli A, Liverini G, Iossa S. (2017). Short-Term Fructose Feeding Induces Inflammation and Oxidative Stress in the Hippocampus of Young and Adult Rats. Molecular Nephrology 55(4): 2869-2883.

[13] Glushakova O, Kosugi T, Roncal C, et al. (2008). Fructose Induces the Inflammatory Molecule ICAM-1 in Endothelial Cells. Journal of the American Society of Nephrology 19(9): 1712-1720.

[14] DiNicolantonio JJ, Mehta V, Onkaramurthy N, O’Keefe JH. (2017). Fructose-induced inflammation and increased cortisol: A new mechanism for how sugar induces visceral adiposity. Progress in Cardiovascular Diseases.

[15] Johnson RJ, Sanchez-Lozada LG, Nakagawa T. (2010). The Effect of Fructose on Renal Biology and Disease. Journal of the American Society of Nephrology 21(12): 2036-2039.

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