The Truth About High Protein Diets and Kidney Damage
Kris Gunnars makes a case for increased protein intake not only to be harmless but potentially even have a protective effect.
A common myth in health and nutrition circles is the idea that eating a lot of protein can harm the kidneys. It does not make much sense, given that humans evolved as omnivores who ate a relatively high protein diet and the fact that we are made of protein. But as with many myths in nutrition, they tend to linger around and often reach a state of dogma, even among health professionals.
The Function of the Kidneys
The kidneys are a remarkable organ. We have two of them, situated next to the vertebral column right under our lowest ribs. Their primary function is to filter substances that we don't need out of the blood. Excess fluid, various electrolytes, toxic by-products of metabolism, and even artificial substances like pharmaceutical drugs.
Among the waste products that the kidneys secrete are the products of protein breakdown, mainly nitrogen. Nitrogen is secreted from the kidneys as urea or ammonia. This has led some people to argue that eating a high protein diet increases stress on the kidneys.
Well, stress is what the kidneys are designed for. They are a remarkably efficient organ that filters about 180 litres of blood per day. Adding protein to the diet has a minimal effect on the total workload of the kidneys.
In a review article published in 2005 , the association of protein intake with kidney health was examined. No evidence was found for high protein diets being detrimental to kidney function in healthy people.
The Two Main Risk Factors for Kidney Failure
There are two main risk factors for kidney failure. These are diabetes and hypertension (elevated blood pressure). Both of these risk factors may play a causal role in the development of kidney disease.
Therefore, if we can improve these factors, then we could argue that increased protein intake might be protective against kidney failure. In type II diabetics, a high protein diet appears to improve blood sugar control along with various other biomarkers of health [2,3].
Additionally, studies in hypertensive patients reveal that increasing protein intake tends to lead to lower blood pressure [4,5].
The Truth About High Protein Intake
People who have kidney disorders may need to watch their protein intake and should do so according to instructions by their doctor. But in otherwise healthy people, there does not appear to be any data to back up the idea that high protein diets could have detrimental effects on kidney function.
If anything, high protein diets appear to have favourable effects on the two most important risk factors for kidney disease. Given other documented health benefits, such as weight loss and improved blood lipids, increasing protein intake should probably be encouraged.
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About the Author
Kris Gunnars is a medical student and a certified personal trainer. He publishes articles on evidence-based nutrition on his website.