Is Eating Too Much Protein Harmful to Your Kidneys?

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Dear Mark,

I am studying to become a nurse and am taking my first nutrition class at a local college. As one of our assignments we had to record everything we ate for an entire week. After looking at my results my teacher was dumbfounded. To make a long story short, my teacher told me that I should only be eating 38 grams of protein each day, and that any more than that could harm my kidneys. I’ve been Primal for 2 years and am healthier than ever. I am 5’2" and a very lean 105 pounds. Should I be concerned?

Renee

Well, Renee, I’m sorry to break it to you, but all those subjective health markers — like being “healthier than ever,” a “very lean 105 pounds,” and satisfied enough to be “Primal for 2 years” — mean absolutely nothing because you are destroying your kidneys by exceeding your daily allotment of six ounces of animal protein. In fact, it’s highly likely that feeling good and maintaining a trim, lean figure are byproducts of impending kidney failure. The human body, you see, is a cruel practical joker dead set on destroying itself (hence the daily internal manufacturing of that poison known as cholesterol); it’s only trying to keep you pacified with regards to your health long enough for outright kidney failure to commence. You should be extremely concerned. I only hope this message reaches you in time.

Seriously, though — the notion that eating more than 0.3g protein per pound of bodyweight (which appears to be how your teacher came to her conclusion) will definitively harm human kidney function leaves me dumbfounded. I’m reminded of the time I had to take Buddha in for a quick checkup at an unfamiliar vet and the woman examining him mentioned that I’d probably want to switch him to a low-protein diet or risk certain renal failure. Because, you know, the kidneys of dogs, close relative of the carnivorous wolf, are unable to process all that meat and protein. It’s ridiculous on its face, and rather than waste a lot of space debunking what Dr. Eades calls one of the “Vampire Myths” (it just won’t die; get it?), I’ll just link to a few papers that have already done so.

There’s this one from the Journal of the International Society of Sports Nutrition, a massive review of the evidence in favor of and in opposition to the AHA’s weasel warnings about “high protein diets,” namely, that people who engage in such risky behaviors as limiting carbs and increasing protein “are [at] risk for … potential cardiac, renal, bone, and liver abnormalities overall.” Long story short: there’s far more evidence in opposition to the claim than evidence in favor of it. The AHA recommendations are at best incorrect and at worst deliberately misleading, and the sum of the actual evidence points to protein as being protective against heart disease, osteoporosis, kidney disease, and liver problems — all things protein is supposed to initiate or worsen.

Another review, this time focusing strictly on whether or not protein intake can precipitate kidney disease in healthy people, is even better. I mean, that’s the important thing, isn’t it? If we want to exonerate or condemn protein, we must study its effects on healthy kidneys. We have to see if it creates problems rather than potentially worsens them. And, according to the exhaustive analysis of Martin et al, there exists no evidence that protein intake negatively influences renal health in otherwise healthy, active individuals. There is some evidence that already impaired renal function might worsen with increased protein, but the experts, as is their wont, can’t resist applying the same recommendations to everyone, regardless of renal health. The result is a nutrition teacher sowing misinformation across the student body in an introductory course, i.e. one that is intended to establish foundational knowledge that the students will carry on through life as a cornerstone of their thinking.

Simply put, healthy kidneys can handle plenty of protein; heck, they are meant to handle protein. One of their primary functions is to process the metabolic waste that results from protein metabolism. Yeah, protein “works” the kidneys, but that’s what they’re there for! Strength training works the muscles. You might even say it strains them. But is that a problem? Compromised kidneys in patients with renal disease (either full-blown or still in development) may not be able to handle as much protein as healthy kidneys, but even that’s up in the air — and protein is not the cause of the problem.

So what causes kidney disease, if not too many deck of cards-sized pieces of deadly animal protein in the diet?

The top two conditions responsible for chronic kidney disease (CKD) are, respectively, diabetes (45% of CKD cases) and hypertension, or high blood pressure.”Even” the Wikipedia entry on renal failure fails to mention “excess protein in the diet” as a cause (even potentially) of CKD. If you have CKD, chances are fairly high that you’re either diabetic, hypertensive, or both.

You know what’s even better? High-protein diets, when compared to the high-carb diet commonly recommended, improve glucose tolerance and blood sugar control in type 2 diabetics without changing kidney function. And, since type 2 diabetes often leads to CKD and is characterized partly by poor glucose tolerance and blood sugar control, you might even say that eating more protein is actually protective against renal failure.

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