The idea that a high-protein diet puts “stress” on the kidneys they’re unable to handle is something that people have been arguing about for years.
It dates back to the early 1980′s when Dr. Barry Brenner proposed a link between high protein diets and the progression of renal disease (renal refers to the kidneys).
In short, the Brenner Hypothesis proposes that eating large amounts of protein on a regular basis has a negative effect on kidney function by increasing both glomerular pressure and renal hyper filtration.
This compromises renal function, which in turn increases the risk for (or the progression of) renal disease.
It’s true that a low-protein diet helps to prevent the deterioration in renal function in patients with renal failure. That’s because one of the main jobs of the kidneys is to remove the end products of protein metabolism from your body.
They act a bit like a sieve, filtering out any unwanted substances in the blood and sending them to the bladder where they can be removed in the urine.
But the majority of scientific evidence cited by Brenner and his colleagues was generated from animal models and patients with existing renal disease.
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While protein restriction may be suitable for treating someone with existing kidney disease, there is no evidence to show that high protein intakes can lead to kidney damage in healthy individuals.
A study by Belgian researchers Jacques Poortmans and Oliver Dellalieux examined the diets of young male athletes to see if their high level of protein intake had any negative impact on kidney function .
One group consisted solely of bodybuilders, while subjects in group two took part in a variety of sports, such as cycling, judo, and rowing.
On average, the bodybuilders consumed about 3,900 calories and 169 grams of protein per day (1.9 grams per kilogram of body weight).
Group two consumed around 2,600 calories and 99 grams of protein daily (1.4 grams per kilogram of body weight). Some of the bodybuilders consumed up to 2.8 grams of protein per kilogram of body weight.
Despite the high levels of dietary protein, blood and urine samples showed that all markers of kidney function were well within the normal range.
In a 12-month study of 68 overweight men and women, a low-carbohydrate diet providing around 130 grams of protein per day had no adverse effects on renal function compared to a high-carbohydrate diet providing roughly 85 grams of protein per day .
University of Connecticut researchers reached a similar conclusion when they reviewed years of research on the subject .
After trawling through dozens of studies on dietary protein and renal function, they found no research carried out on healthy individuals to demonstrate a clear link between increased dietary protein intake and a detrimental “strain” on the kidneys.
Their conclusion reads as follows:
“Although excessive protein intake remains a health concern in individuals with pre-existing renal disease, the literature lacks significant research demonstrating a link between protein intake and the initiation or progression of renal disease in healthy individuals.
“More importantly, evidence suggests that protein-induced changes in renal function are likely a normal adaptive mechanism well within the functional limits of a healthy kidney. Without question, long-term studies are needed to clarify the scant evidence currently available regarding this relationship.
“At present, there is not sufficient proof to warrant public health directives aimed at restricting dietary protein intake in healthy adults for the purpose of preserving renal function.”
When researchers from Florida’s Nova Southeastern University compared two protein intakes over an 8-week period – 2.3 grams of protein per kilogram (1 gram per pound) versus 3.4 grams of protein per kilogram (1.5 grams per pound) of bodyweight per day – they found no evidence to suggest that the high intake of protein had any kind of adverse effect on the kidneys .
Despite the high levels of dietary protein, markers of kidney function remained well within the normal range.
What’s more, there are estimates that some of your Paleolithic ancestors consumed upwards of 230 grams of protein per day. For someone weighing around 176 pounds (80 kilograms), that works out at 1.3 grams per pound of bodyweight (2.9 grams per kilogram).
Protein has formed a safe part of the human diet for many years, and there’s no good reason to believe that this level of intake is unhealthy or unsafe.
1. Ideura, T., Shimazui, M., Higuchi, K., Morita, H., & Yoshimura, A. (2003). Effect of nonsupplemented low-protein diet on very late stage CRF. American Journal of Kidney Diseases, 41, S31-S34
2. Poortmans, J.R. & Dellalieux, O. (2000). Do regular high protein diets have potential health risks on kidney function in athletes? International Journal of Sport Nutrition and Exercise Metabolism, 10, 28-38
3. Martin WF, Armstrong LE, Rodriguez NR. (2005). Dietary protein intake and renal function. Nutrition & Metabolism, 2, 25
4. Antonio J, Ellerbroek A, Silver T, Orris S, Scheiner M, Gonzalez A, Peacock CA. (2015). A high protein diet (3.4 g/kg/d) combined with a heavy resistance training program improves body composition in healthy trained men and women – a follow-up investigation. Journal of the International Society of Sports Nutrition, 12, 39
5. Brinkworth GD, Buckley JD, Noakes M, Clifton PM. (2010). Renal function following long-term weight loss in individuals with abdominal obesity on a very-low-carbohydrate diet vs high-carbohydrate diet. Journal of the American Dietetic Association, 110, 633-638
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