I was reading a post by Dr Eades recently, where he was examining a study which showed that high-dose thiamin (vitamin B1) may be an effective treatment for diabetic nephropathy, when I came across an interesting response to a comment.
The commenter was talking about how his friends and family give him a lot of grief about his high protein diet. They are concerned that all the protein may cause damage to his kidneys, so they encourage him to eat more “heart healthy grains.”
Dr Eades responded to this comment by saying… “The idea that protein damages the kidney is a myth. It’s the elevated glucose that causes the damage, the protein leak is the effect.”
In truth, the myth has been around forever. And there’s no research to back it up. Although studies have shown that in individuals with pre-existing unhealthy kidneys, excessive protein may indeed cause undue strain on the kidneys. There’s not one scientific study, using healthy adults with normal kidney function, which has shown that excessive protein causes kidney damage.
In fact, quite the contrary….
In one study, researchers examined the renal (kidney) function of bodybuilders and other well-trained athletes with a high and medium protein diet. The athletes underwent a 7-day nutrition record analysis as well as blood sample and urine collection to see if a high and medium protein diet affected kidney function.
The study found that both groups of athletes had renal clearances of creatinine, urea, albumin, and glomular filtration rates that were within the normal range. The authors concluded “there were no correlations between protein intake and creatinine clearance, albumin excretion rate, and calcium excretion rate.” In other words, a high protein diet does not impair kidney function in well-trained athletes, at least in the short term.
More recently, researchers investigated the effect of protein intake on renal function in women over an 11-year period. The study involved 1624 women who were enrolled in the Nurses’ Health Study, were 42–68 years of age in 1989, and gave blood samples in 1989 and 2000.
The study found that high protein intake was not significantly associated with change in estimated glomerular filtration rate in women with normal renal function. The authors concluded “high protein intake was not associated with renal function decline in women with normal renal function.”
From the results of these two studies you can see that there is no evidence that high protein diets are harmful to the kidneys of healthy athletes and women. It’s elevated glucose that causes the damage….