High protein consumption puts a strain on your kidneys. Most of us heard this statement multiple times. Let’s shed light on this topic and see
- where this belief comes from
- how much truth is there in this statement and
- if the protein source matters
Scientific background
More than 30 years ago, a scientist named Brenner established a hypothesis that excessive dietary protein consumption can compromise kidney function.1
To assess kidney function scientists use a parameter called glomerular filtration rate (GFR). This parameter gives an estimate how fast kidney can remove body’s waste products from the circulating blood. GFR value below the normal range suggests that the filtration mechanism does not function properly.2 Brenner suggested that GFR above the normal range also has a negative effect by increasing pressure inside the kidneys. This can lead to structural changes and cause injury.
However, it is controversial if Brenner’s hypothesis is valid for healthy individuals. Most of the research studies Brenner used to establish his hypothesis were conducted on animals or on people with impaired kidney function. There is no evidence in scientific literature that high protein consumption causes kidney damage in healthy individuals.1
In contrast, some professionals suggest that increased GFR is a normal physiological adaptation to altered conditions - higher protein intake in this case - and not a risk factor for chronic kidney disease in healthy individuals.3 Also pregnant women show an increase in GFR. However, pregnancy is not considered as a risk factor for kidney diseases.1
Is there any difference between animal and plant protein sources?
Protein source seems to have an influence on glomerular filtration rate. Research studies have shown that plant protein does not increase GFR to the same extent as animal protein does, at least when consumed in the 1 g/kg range.2,3 However, when the dietary plant protein intake was increased up to 2.6 g/kg day, also subjects on a vegan diet showed an increase in GFR.2
Another indicator for kidney malfunction is the presence of protein in urine. Healthy kidney should retain protein in the circulating blood. Also here protein source seems to play a role. In the past, the consumption of animal protein was associated with the presence of protein in urine, while plant protein consumptions was not.4
What about patients with chronic kidney diseases?
Patients with chronic kidney diseases are advised to follow a low protein diet to limit further progression of kidney disease. Bernstein and colleges reviewed the effect of plant vs. animal protein sources on patients with kidney disease. They came to the conclusion that although some studies suggest that high vegetable protein consumption does not have the same effect on the progression of kidney disease as diet high in animal protein, also vegetable protein is likely to accelerate the progression of kidney disease when consumed in large amounts.2
Nevertheless, the protein source is important for patients with chronic kidney diseases, as they are advised to follow a phosphorous restricted diet. In this context plant protein sources are superior to animal protein as they contain less bioavailable phosphorous.5
Bottom line
Although high protein consumption has negative impact on some individuals, such as patients with impaired kidney function, it is highly controversial if high protein consumption affects healthy individuals’ kidney function. To my knowledge, there is no scientific evidence that high protein consumption can impair kidney function of healthy individuals. Some healthy populations, such as athletes, habitually consume a high protein diet (2.0 g/kg/day) without exhibiting greater odds for kidney diseases.1
Side note
To be on the safe side, it is recommended to undergo medical screening (serum creatinine level and a urinary dipstick test) before adapting a high protein diet.6
However, there are several factors that effect creatinine levels in the human body.7,8 For this reason, professionals should be careful about the interpretation of test results. There is a risk for misdiagnosis of kidney disease for individuals who
- have muscle mass than the average population
- are on high protein diet
- supplement with creatine
- exhibit thyroid dysfunction
References:
(1) Martin, W. F.; Armstrong, L. E.; Rodriguez, N. R. Nutr. Metab. (Lond).2005, 2, 25.
(2) Bernstein, A. M.; Treyzon, L.; Li, Z. J. Am. Diet. Assoc.2007, 107, 644–50.
(3) Thomas, D. M.; Coles, G. a; Williams, J. D. Kidney Int.1994, 45, 411–6.
(4) Lin, J.; Hu, F. B.; Curhan, G. C. Clin. J. Am. Soc. Nephrol.2010, 5, 836–43.
(5) Moe, S. M.; Zidehsarai, M. P.; Chambers, M. a; Jackman, L. a; Radcliffe, J. S.; Trevino, L. L.; Donahue, S. E.; Asplin, J. R. Clin. J. Am. Soc. Nephrol.2011, 6, 257–64.
(6) Johnstone, A. M. Proc. Nutr. Soc.2012, 71, 339–49.
(7) Iglesias, P.; Díez, J. J. Eur. J. Endocrinol.2009, 160, 503–15.
(8) Willis, J.; Jones, R.; Nwokolo, N.; Levy, J. Br. Med. J.2010, 340, 210–211.