Today, we will read about can protein rich diet cause kidney damage and bone loss? Lets find out.

Where did this myth come from?

Well way back in 1920, the paper was published in the Journal of biological chemistry suggesting that increasing protein in the diet led to increased calcium excretion in the urine. About 50 years later in the 1970s and 80s. The group of metabolic balance studies found that even when dietary calcium intake was controlled for dietary protein intake wasn’t affecting intestinal absorption of calcium but yet still piles of other research dating all the way back to the 1920s have been showing repeatedly that increased dietary protein leads to increased urinary excretion of calcium.

The reasoning went that sense more calcium wasn’t being absorbed into the blood from the intestine that extra calcium being seen in the urine had to be coming from somewhere. That somewhere was probably from the bones. This eventually developed into the so called acid-ash hypothesis, which for our purposes states that the extra amino acids from an increase in dietary protein lead to a state of acidosis in the body and the body tries to compensate and buffer that acidity by releasing alkaline stores in the bones leading to a loss of calcium and eventual osteoporosis.

Where did it go wrong?

The key error was in the old studies from the 1970s and 80s and they were simply mistaken about their claim that increased dietary protein wasn’t affecting intestinal calcium absorption.

According to a 2007 teen systematic review from the National Osteoporosis foundation improved dietary intervention studies have revealed using dual stable calcium isotopes increasing dietary protein was associated with a significant increase in intestinal calcium absorption, such that nearly the entire increase in the urinary calcium could be accounted for by improved calcium absorption.

In a short-term there is no increase in skeletal catabolism so basically taking in more protein in the diet, simply led to more calcium being absorbed in the intestines which led to more calcium in the blood and then eventually more calcium in the urine. So most of that increase in urinary calcium excretion was just coming from the diet to begin with. So the entire acid ash hypothesis at least in the context of a higher protein diet causing bone loss is based on an outdated and erroneous finding. Now even if the acid ash hypothesis were true, even if protein induced acidosis were causing bone mineral loss more recent studies have shown that these acid based concerns are minor when compared to the alkalizing effects of eating more fruits and vegetables. So we think more focus should be placed on eating more fruits and vegetables and less focus should be placed on eating less protein.

The National Osteoporosis foundation notes that 50% of bone by volume is protein. They conclude that current evidence shows no adverse effects of higher protein intakes. There were actually some positive trends between bone mineral density and dietary protein at most bone sites, especially the lumbar vertebrae.

Where did this myth come from?

The kidney myth is based on the correct idea that increasing dietary protein in patients that have pre-existing kidney dysfunction contributes to a further deterioration of kidney function. This is a common move, we think we’ll see in a lot of these nutrition based myths it’s assumed that because something is bad for people who already have a certain disease that thing must somehow contribute to the cause of that disease. It’s similar to the argument that because diabetics need to monitor and regulate their sugar intake the sugar must play a central causative role in the development of diabetes.

A 2015 review paper published in the Journal of applied physiology, nutrition, and metabolism concluded that the belief that higher protein intakes lead to renal failure has no foundation. In fact the response to an increase in dietary protein intake in those with normal renal function is actually an increasing glomerular filtration rate or GFR sign of improved kidney function.

In 2007, The World Health Organization agreed that while there is clear evidence that high protein intakes by patients with kidney disease does contribute to the deterioration of kidney function.The idea that the decline of GFR that occurs with advancing age and healthy subjects can be attenuated by reducing protein and the diet appears to have no foundation.

That’s two myths busted, it doesn’t seem to be the case that a high protein diet puts you at a greater risk of bone loss or kidney dysfunction or renal failure. In fact it seems like a high protein diet may actually help with these things and not only that but also decrease rates of age-related sarcopenia and help with body composition improve weight management and appetite control.