A claim you hear on longevity podcasts

Is a high-protein diet safe for healthy kidneys?

Strong consensus for. Of 10 studies that test it, 7 agree, 2 partly agree and 1 disagrees.

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The claim checked: A high-protein diet does not harm healthy kidneys Hear it at 1:01:29

What do the studies say?

Strong consensus for

Seven of ten studies found no harm to kidney function from more protein in adults without kidney disease. Two found filtration rose and urged caution, and one Korean cohort linked the top quarter of intake to faster eGFR decline.

Computed from 10 studies that test this point, each judged by two readers, in full. 8 more studies are waiting for a full read and do not count yet.

The study behind the claim tested something else. See what it tested

The study behind the claim tested something else. See what it tested

What was said on the podcast?

“if you have chronic kidney disease and or, you know, you're on the way to or or need dialysis, it's a completely different question, right? Uh you need absolutely speak to your renal team. That's that's the important thing you need to do. But for people with with normal healthy kidneys, eating you know, there's no negative effect of of protein intake on kidney function.”
Tommy Wood, a guest on Feel Better, Live More · #1 Neuroscientist: "Even A Little Bit Of Alcohol, Caffeine & Sugar Does This To You!" Dr Tommy Wood · 1:01:29 on YouTube
Comes up in 11 episodes of the show.
The study behind the claim The retelling overstates it

What did the study actually test?

On tape (Rhonda Patrick, solo): research in athletes at 3.2 to 4.5 g/kg a day for up to one year found no adverse change in kidney function. The study fits the direction: no harmful change in its kidney markers. But the high-protein phases averaged 3.32 g/kg and added up to 6 months inside the year, the comparison diet was already 2.51 g/kg, the people were 14 trained men, and no arm reached 4.5 g/kg. A High Protein Diet Has No Harmful Effects: A One-Year Crossover Study in Resistance-Trained Males. J Nutr Metab, 2016. Randomized crossover: habitual diet and a higher-protein diet alternated in 2- and 4-month blocks over one year; serum BUN, creatinine and eGFR, 14 healthy resistance-trained men, mean age 26.

What was saidWhat the study did
What was given Differs 3.2 to 4.5 g/kg of protein a day for up to one year About 3.32 g/kg a day in the high-protein phases, 6 months in total inside a one-year crossover; no arm at 4.5 g/kg
Compared with Matches A lower, usual protein intake The men's habitual diet, already about 2.51 g/kg a day
What was measured Matches Adverse changes in kidney function Serum BUN, creatinine and eGFR
Who took part Differs Athletes 14 healthy resistance-trained men

What it found

“There were no significant differences between the normal and high groups in any measure of health or body composition (Tables 3 and 4 ).”

PMID 27807480

How the authors extend it

“Our investigation discovered that, in resistance-trained men that consumed a high protein diet (~2.51-3.32 g/kg/d) for one year, there were no harmful effects on measures of blood lipids as well as liver and kidney function.”

PMID 27807480

No grant is stated. Dymatize provided the protein powder; the first author is CEO of the International Society of Sports Nutrition, which Dymatize sponsors. Two readers agreed on the label, and the paper was read in full.

The study behind the claim The retelling overstates it

What did the study actually test?

On tape (Gabrielle Lyon, guest, April 2022): a recent meta-analysis says protein helps and increases glomerular filtration rate, so it increases the efficiency of our kidneys. Most likely this meta-analysis; Schwingshackl 2014 (PMID 24852037) also found higher GFR. The pooled trials found GFR slightly higher after high protein, a trivial effect, and no difference in the change in GFR. The authors conclude no harm; they claim no benefit or efficiency gain. 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. Systematic review and meta-analysis of randomized trials (longer than 4 days) comparing higher- with normal- or lower-protein diets on GFR, 28 trials, 1,358 adults without kidney disease.

What was saidWhat the study did
What was given Matches Eating more protein High-protein diets (at least 1.5 g/kg a day, 20% of energy or 100 g a day)
Compared with Matches Less protein Normal- or lower-protein diets
What was measured Matches Higher GFR, more efficient kidneys GFR: trivially higher after high protein, no difference in its change
Who took part Matches People in general, with healthy kidneys Adults without kidney disease

What it found

“The post-only comparison showed a trivial effect for GFR to be higher after HP intakes [standardized mean difference (SMD): 0.19; 95% CI: 0.07, 0.31; P = 0.002].”

PMID 30383278

How the authors extend it

“Postintervention GFR comparisons indicate that HP diets result in higher GFRs; however, when changes in GFR were compared, dietary protein had no effect.”

PMID 30383278

Not stated in the text read. One author reports research funding, travel support and honoraria from the US National Dairy Council, Dairy Farmers of Canada and the US National Beef Cattlemen's Association. Two readers agreed on the label, and the paper was read in full.

The point checked Strong consensus for

For people with normal, healthy kidneys, a high-protein diet has no negative effect on kidney function

Agree 7

controlled trial · 2013

“The low-carbohydrate diet was at least as effective as the Mediterranean or low-fat diets in improving eGFR, an effect likely mediated in all three diets by the weight loss-induced improvement in blood pressure and in insulin sensitivity.”

Renal function following three distinct weight loss dietary strategies during 2 years of a randomized controlled trial. Diabetes Care
Who: Overweight or obese adults (mean age 51, 86% men, mean BMI 31) in Dimona, Israel, with or without type 2 diabetes (n=45) or coronary heart disease; serum creatinine below 176 umol/L; baseline eGFR 30-151, with 31% at eGFR 30-60 (CKD stage III) and 69% above 60; 23 had microalbuminuria at baseline. Not a pure normal-kidney population.
PMID 23690533

controlled trial · 2012 · landmark

“In conclusion, this study, the longest and most comprehensive to date on the effects of a low-carbohydrate high-protein diet on renal function, revealed that the diet was not associated with noticeably harmful effects on GFR, albuminuria, or fluid and electrolyte balance compared with a low-fat diet in obese individuals without pre-existing kidney disease.”

Comparative effects of low-carbohydrate high-protein versus low-fat diets on the kidney. Clin J Am Soc Nephrol
Who: 307 obese adults (208 women, 99 men), aged 18-65, mean age 45.5, mean BMI 36.1, without serious medical illness (type 2 diabetes, BP 140/90 or more and lipid-lowering drugs excluded), with normal baseline serum creatinine and cystatin C, at three US academic centers
PMID 22653255

pooled analysis · 2018 · landmark · cited on tape

“These findings once again suggest that consuming an HP diet does not negatively affect kidney function in healthy individuals.”

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
Who: Adults aged 23-72 (mean 49) without CKD who were healthy, obese, hypertensive and/or had type 2 diabetes (type 1 diabetes, CKD, proteinuria and previous stones excluded); normal-weight to obese, BMI 21.2-36.1
PMID 30383278

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other primary study · 2016 · cited on tape

“In brief, we found no deleterious effects of a high protein diet (2.51–3.32 g/kg/d) over a 1-year period.”

A High Protein Diet Has No Harmful Effects: A One-Year Crossover Study in Resistance-Trained Males. J Nutr Metab
Who: 14 resistance-trained young males (10 white, 3 black, 1 Pacific Islander), healthy; baseline eGFR 95 ± 19 (all values reported as ≥60 mL/min/1.73 m2) and creatinine within reference range; randomized crossover habitual vs high protein
PMID 27807480

controlled trial · 2016

“There were no changes in blood lipids as well as renal or hepatic function.”

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
Who: 12 resistance-trained healthy men, age 25.9 ± 3.7 y, ~7.6 y training; baseline eGFR 96 ± 20 mL/min/1.73 m2 and creatinine within reference range; randomized crossover
PMID 26778925

controlled trial · 2010

“Concerns that diets high in protein may have deleterious effects on renal function were not supported by the results of this study.”

Protein-enriched meal replacements do not adversely affect liver, kidney or bone density: an outpatient randomized controlled trial. Nutr J
Who: 100 overweight or obese men and women (BMI 27-40, age >30, mean 49.4 y, mostly women) in good health by history, exam and screening labs; type 2 diabetes and glucose intolerance excluded; kidney function normal by routine labs; 70 completed
PMID 21194471

systematic review · 2018

“Based on the evidence reviewed herein, higher protein intake, at least within the short term, and within the range of DRIs, is consistent with normal kidney function in healthy individuals.”

A Systematic Review of Renal Health in Healthy Individuals Associated with Protein Intake above the US Recommended Daily Allowance in Randomized Controlled Trials and Observational Studies. Adv Nutr
Who: Healthy free-living adults >18 y with normal GFR ≥90 mL/min/1.73 m2 (and AER ≤30), with or without metabolic risk factors (mild hypertension, hyperlipidemia, type 2 diabetes without microalbuminuria, obesity); CKD excluded; weight-loss studies excluded
PMID 30032227

Partly agree 2

pooled analysis · 2014 · landmark

“However, considering of the fact that subclinical CKD is highly prevalent, and that obesity is associated with kidney disease, weight reduction programs recommending HP diets especially from animal sources should be handled with caution.”

Comparison of high vs. normal/low protein diets on renal function in subjects without chronic kidney disease: a systematic review and meta-analysis. PLoS One
Who: Adults 18 and older without CKD (trials enrolling people with GFR below 60, type 1 diabetes or macroalbuminuria excluded; microalbuminuria allowed): healthy, overweight, obese and type 2 diabetic participants, mean age 22.3-67 years, about two thirds of trials in obese subjects
PMID 24852037

controlled trial · 2013 · landmark

“These findings suggest that increased protein intake might have adverse consequences on kidney function in the long term.”

Effect of a high-protein diet on kidney function in healthy adults: results from the OmniHeart trial. Am J Kidney Dis
Who: Healthy adults aged 30 and older with prehypertension or stage 1 hypertension in Boston and Baltimore, mean age 53.5, 55% African American, 45% women, mean BMI 30.2; diabetes, kidney disease (eGFR below 60) and cardiovascular disease excluded; baseline cystatin C eGFR 92.0
PMID 23219108

Disagree 1

other primary study · 2020 · landmark

“These findings suggest that a high-protein diet has a deleterious effect on renal function in the general population.”

High-protein diet with renal hyperfiltration is associated with rapid decline rate of renal function: a community-based prospective cohort study. Nephrol Dial Transplant
Who: 9,226 Korean community-dwelling adults aged 40-69 (KoGES, Ansan/Ansung) with eGFR >=60 mL/min/1.73 m2 and no underlying kidney disease at baseline (mean eGFR 93.9); validation in 40,113 KNHANES adults with eGFR >=60 (cross-sectional, RHF only)
PMID 31172186

What else was said but not tested?

  • If you have chronic kidney disease or are on the way to dialysis, it is a completely different question for your renal team
  • Eating protein above your needs makes the kidneys work harder to clear the extra nitrogen, which is part of their job

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