The Real Effects of a High Protein Diet

Protein, Kidney Health, and Body Composition

What happens when you consume a very high protein diet? Like 700% more than RDA guidelines? Here’s the actual science.


The High Protein Diet Examined

Ever been accused of eating too much protein? If you have, you’ve probably been told that your kidneys will explode from consuming such a high protein diet.

I hear this all the time. In fact, when I teach exercise physiology, I challenge my students to see if they can find a peer-reviewed study showing that in healthy people, too much protein will damage their kidneys. Can you guess what they find?

Nothing, nada, zilch, zip. The data does not currently exist.

Then why does this myth exist? Part of the reason is that eating more protein will increase the amount of work your kidneys have to do. Markers such as creatinine (NOT creatine) and GFR (glomerular filtration rate) may go up, indicating that your kidneys are working harder. But does that mean there’s any indication of damage? Let’s find out.

Protein and Kidneys: The Science

Here’s a quote to get us started:

From Phillips, SM 2014: “An examination of the statements made by both the Institute of Medicine in setting the protein RDA in North America, as well as the World Health Organization’s report on protein intakes, indicates there is no evidence linking a higher protein diet to renal disease.”

According to two top agencies, the risk of kidney damage in healthy subjects appears to be slim. So the dangerous-protein myth is not looking good.

“Prolonged intake of a large amount of protein has been associated with potential dangers, such as bone mineral loss and kidney damage. In otherwise healthy individuals, there is little evidence that high protein intake is dangerous. However, kidney damage may be an issue for individuals with already existing kidney dysfunction.” (Tipton KD, 2011).

So far, it appears that having your kidneys do more work is not a bad thing in itself. When you go to the gym to do an arm workout, your biceps do more work, and as a result, they get bigger (hypertrophy). Could the same thing happen with your kidneys?

Researchers in 2015 found that increasing protein did require the kidneys to do more work; however, it did not damage them (no increase in microalbuminuria, which indicates damage). Your kidneys, like your biceps, will get bigger with more work, but that growth is not from any damage. They were just adapting to the stress placed on them.

So, the current data just doesn’t support the assertion that protein is dangerous. But what if you’re a hard-training lifter and you consume a metric ton of protein?

Show Me The Studies

If you’re a bodybuilder or athlete, you don’t do things normal people do. Thus the standard pencil necks used in most studies don’t apply. But these do.

One of the first studies on protein was by Poortmans JR and Dellalieux O., who suggested that excess protein is hazardous to the kidneys. This study investigated bodybuilders and other well-trained athletes with high and medium protein intake.

So what did they find? Well, while those who ate a high protein diet did have higher plasma concentrations of uric acid and calcium, the bodybuilders had normal renal clearances of creatinine and urea (waste products). Scientists concluded that protein intake under 2.8 g/kg did NOT impair renal function in well-trained athletes.

Another study was done by Brandle and colleagues. While the study wasn’t perfect, it was the first to look at the effects of protein on kidney function. They found no correlation between albumin excretion rate (urinary albumin arguably being a damage variable) and gross protein intake (as assessed by nitrogen excretion rate).

What About Body Comp and Fat Gain?

A study done by Dr. Jose Antonio and colleagues took it to the extreme by looking at heavy benching dudes consuming lots of protein.

They did what’s called a “randomized crossover design” on resistance-trained male subjects. The dudes lifted and ate copious protein. The average bench press at baseline was 126.4 kg, which is 278 pounds for those who think the metric system was invented just to torture you.

For eight weeks, participants scarfed down a high protein diet at over 3 grams per kilogram, per day – which for a 220-pound person is 300 grams of protein per day. They coupled it with a periodized heavy resistance training program. During the other 8-week period, they consumed their normal, lower protein diet.

The results? Even though the high protein group was eating more calories in the form of protein, there were no significant changes in body composition – they didn’t get fat despite the increased calories. Nor did they see changes in markers of health in either group (blood lipids, glucose, renal, kidney function, etc.).

Despite consuming massive amounts of protein, their kidneys did not launch an attack to exit their low back due to the high protein intake. To further back up their point, researchers did a subanalysis on two subjects who ate the most protein in the study. They didn’t find any renal (kidney) issues despite these two subjects consuming 483-724% over the RDA for protein.

Need More Proof?

You could argue that this data is still short-term. Most lifters have been eating high protein for years to decades. What about 6 months into their high-protein eating plan? What happens to their kidneys then? Dr. Jose Antonio published a one-year study. Yep, one year. In terms of scientific research, that’s a freaking eternity.

They took fourteen healthy resistance-trained men who’d been training an average of almost nine years for a randomized crossover design study. They had them consume their normal diet altered with a high protein version (>3 g/kg/d) so that, on average, each subject was on each version for 6 months.

They found that, for those who consumed a high protein diet (about 2.5-3.3 g/kg/d) for one year, there were no harmful effects on measures of blood lipids as well as liver and kidney function.

And despite the increase in total calories during the high protein phase, subjects did not gain fat. Yep, tons of protein for a year in high-level trainers with free-living humans. It doesn’t get much better than that for scientific data.

Protein: Maybe You Need More?

Out of all the things you could do to improve your health, performance, and body composition, worrying about too much protein is WAY down on the list. In fact, if you’re going to worry about protein at all, it might make more sense to worry about not getting enough.

Most people I work with do much better by increasing their protein intake. Obviously, this doesn’t give you free rein to consume 400+ grams of protein every day for years to prove some lab coat nerd wrong. At some point it would be bad. Too much is too much. After all, even too much water can kill you too.

But the data that protein is harmful to your kidneys is just NOT there. Sit back, relax, have a high-quality protein shake, and your kidneys will be just fine.

The metabolism-boosting, award winning protein:

References

References

  1. 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;2016:9104792. PubMed.
  2. Antonio J et al. The effects of a high protein diet on indices of health and body composition–a crossover trial in resistance-trained men. J Int Soc Sports Nutr. 2016 Jan 16;13:3. PubMed.
  3. Brändle E et al. Effect of chronic dietary protein intake on the renal function in healthy subjects. Eur J Clin Nutr. 1996 Nov;50(11):734-40. PubMed.
  4. Bie P et al. Dietary protein and kidney function: when higher glomerular filtration rate is desirable. Am J Clin Nutr. 2015 Jul;102(1):3-4. PubMed.
  5. Lowery LM et al. Dietary protein safety and resistance exercise: what do we really know? J Int Soc Sports Nutr. 2009 Jan 12;6:3. PubMed.
  6. Phillips SM. A Brief Review of Higher Dietary Protein Diets in Weight Loss: A Focus on Athletes. Sports Med. 2014;44(Suppl 2):S149-153. PubMed.
  7. Poortmans JR et al. 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. PubMed.
  8. Tipton KD. Efficacy and consequences of very-high-protein diets for athletes and exercisers. Proc Nutr Soc. 2011 May;70(2):205-14. PubMed.
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Outstanding article! I went through my own little circle of medical testing Hell dealing with individuals that didn’t quite appreciate the significance of increased musculature, increased protein intake and the impact of lab results, but on the plus side I got to have a nephrologist document in my medical file that I carried an “abnormal amount of muscle mass for a (then) 36 year old male”. So that was cool.

Other champions of high protein intake include Jon Andersen, who hosted an “Ask me Anything” here on the forums

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goals

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I think the issue is that the medical data does show that people known to have kidney issues should not do anything to make those issues worse and most people have no idea if their kidneys are functioning properly.

I didn’t know mine were not until it I was in stage 3b of CKD. MRIs and date showed I did have an issue.

Nearly too late.

So it isn’t whether or not the average person or “well trained athlete” can have 700% of RDA of protein, but whether or not it’s a good idea to do anything without knowing where you are prior to starting.

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They didn’t get fat, but no significant changes in body composition also means they didn’t see significant gains in muscle mass.

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Search for “cystatin c” blood test for helpful info and the posts by @mnben87, myself, and others.

Excellent!

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The human body is wonderfully adaptable and thrives on many kinds of diet. Most people in the United States get lots of protein in their diet. It makes sense for people training to become muscular to consume more than the average person, especially if younger and just starting training, when muscle growth is fastest. You need calories from somewhere and it is usually a better source than simple sugars.

Microalbuminuria is only one sign of possible renal concerns, and microscopy for cells, casts, proteinuria and hematuria can sometimes be significant. Although reasonable amounts of protein are safe, results from a one year study only applies to a similar population for that length of time. But damage can occur gradually and take more than a decade to become significant.

People who have gout benefit from a diet lower in purines. Everybody has decreased creatinine clearance (reduced kidney function), as they age. This does not make eating lots of protein bad, but the aged group was presumably not the population similar to the studied weightlifters. One has to be cautious about extending the results of a study to different populations, and doing something for 20 years is not the same thing as doing it for one year.

If people get their blood tested once a year for glucose (to screen for diabetes) and creatinine (as the best measure of kidney function), this will go a long way to being confident you can eat larger amounts of protein. Adding a urea and urinalysis would further increase confidence. Men, especially 18-45, do not always get yearly blood work (often need to be prodded to go to the doctor if feeling generally well), and so do not always know if they are part of the small minority of people who may be at increased risk from very high protein intake (such as those with nephrotic or nephritic syndromes, prediabetics, those with more obscure renal or metabolic disorders, those predisposed to gout or calculi, those with a family history of the above, etc.)

While I certainly do agree with the premise of the article that the “harmful” effects of high protein diet are overblown, it is also relevant to note that many of these studies have been done by scientists who are funded by supplement companies (as they declare in the “Competing Interests” section of the papers). This certainly does not negate the findings, but it is important to remember a quote by the famous scientist John von Neumann: “With four parameters I can fit an elephant, with five I can make him wiggle his tail”.

Great article. May have to steal this to send to my dietitian who when I told her this week I am targeting 250-280 grams protein per day (roughly .8 -1.0 g/lb) balked at the idea. Suggested only 1/4 of my plate be protein (i don’t believe I have done that lttile since starting lifting at 15 years old).

I get regular blood tests (quarterly do to diabetes) and never has my kidney function been anything but normal.

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You misunderstood your dietician.

She’s saying you need a bigger plate.

Something like this

image

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How did i miss that obvious solution?
I am a crappy engineer…

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