What Excessive Protein Consumption Does To Your Kidneys, According To Science

Fitness coach breaks down common myth...

Protein is an essential amino acid that plays an incredibly important role in the body’s overall function. In fact, every single cell in your body requires protein to function and to remain strong. It affects everything from the health of your organs to the condition of your hair. It’s also no secret that it can help determine how swole we can become in the gym, with ‘gym bros’ on a never-ending quest to consume as much as humanly possible.

However, for all its benefits, there are often claims to suggest too much protein can have damaging effects on your body. The daily recommended amount of protein is 0.8g/kg of bodyweight – although some experts claim you should base this figure on lean body mass instead – with those looking to pile on the muscle aiming for around 1 – 1.3g/kg.

A long-held belief has suggested going over this figure on a regular basis could have a devastating effect on your kidneys because it causes them to work overtime to clear the metabolites (the end product of metabolism).

But is that true?

Fitness coach James Kew recently took to Instagram to credit @physiqonomics with a post that claims high-protein diets actually have very little effect on the health of your kidneys, although this goes on the basis that your kidneys are healthy. If, however, you have existing renal disease (where your kidneys are already damaged and so don’t function at 100%) then you will need to keep a closer eye on your protein intake.

These results stemmed from a 2003 Nurses’ Health Study, which examined the GFR (glomerular filtration rate i.e. the flow rate of filtered fluid through the kidneys) of people with pre-existing renal disease over an 11-year period. The study found an increase in protein intake did result in a further decline in overall kidney function.

But for those with healthy kidneys, the results differed. The same study also examined 1,135 women with kidneys in tip-top shape and found high protein intake had little effect on GFR, concluding “a high protein diet was not associated with kidney damage in women with normal renal function.”

Further studies by Poortmans and Dellalieux and Antonio et al. looked specifically into the effects of protein intake in bodybuilders and trained athletes. These studies saw participants consuming protein levels as high 2.8g/kg to 3.4g/kg (way over the recommended daily amount) and found neither level to impair kidney function.

That said, even though a high protein diet won’t (as far as we know) damage healthy kidneys, researchers and industry experts continue to recommend you don’t exceed the 0.8g/kg level, primarily because you don’t really need to.

Previous studies have found the optimal protein dosage to be around 1g – 1.25g… Any higher and you won’t see much of a difference. The quality of the protein is also important, with virtually everyone agreeing that animal sources provide greater quality compared to plant-based, alongside the argument that humans are biologically built to be omnivores.

Something to mull over your next steamed chicken breast fillet.

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