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 and a very lean 105 pounds. Should I be concerned?
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.
As for hypertension, the latest systematic review concludes that more protein in the diet seems to correlate with lower, or at least normalized, blood pressure in humans. That doesn’t necessarily mean anything definitive, but it’s certainly interesting, and it doesn’t support the standard position.
Of course! Anyway, unless it’ll compromise your grade in the class, I’d speak up about it. Engage your teacher, for without disagreement, especially when warranted, there can be no progress. At the very least, defend your stance, perhaps wielding the aforementioned papers, and by all means: don’t feel the need to limit yourself to 38 grams of protein per day! While that may be adequate – that is, you’ll live – you definitely have room for more.
It provides amino acids, which play multiple roles in the human body. They act as building blocks for most bodily structures, including hair, organs, skin, and muscles. Using amino acids, we build new tissue and repair damaged tissue. Lifting weights “damages” muscle tissue; we repair the damage with amino acids. Amino acids also act as precursors to hormones and neurotransmitters, like serotonin (the amino acid tryptophan) and dopamine (the amino acid tyrosine).
It’s good for satiety. Younger and older men eating 1g protein per kg of bodyweight had greater satiation than similarly aged men eating either 0.75g/kg or 0.5g/kg, and they reported a superior ability to stick to an eating plan.
(Animal protein is best, of course. A recent study found that due to reduced bioavailability of plant protein, vegetarians should probably increase their total protein intake to make up for the deficiency.)
Most people don’t need a ton of protein. If asked, I say I eat roughly 1 gram per pound of bodyweight, but it’s not something I’m militant about and I’m no longer hitting the weights like I used to. I just eat to satiety. Since it’s a satiating macronutrient, I find there’s a natural, relatively organic limit to how much pure protein I even want. Lean chicken breasts? I’m lucky if I can get through a whole one. A nice juicy grass-fed ribeye festooned with fat? I’m licking the plate.
Other people will need more protein. Highly active athletes, Crossfitters, powerlifters, folks trying to gain mass and strength, folks trying to lose a bunch of weight – they all can benefit from an increased protein intake, either by increasing satiety (thus improving diet adherence) or providing amino acids for muscle recovery and repair. One gram or protein per pound of lean body mass is a good average number to shoot for over a range of a few days.
Renee, if you’re feeling good with your current level (how much protein are you eating, by the way?), you’re performing well, you’re lean (and you apparently are), and you’re healthy (free of diabetes and hypertension), I don’t see any reason to curtail your protein intake. And certainly not because it’s going to destroy your kidneys. There is some contention that protein restriction (or protein cycling) can extend lifespan, but as I said in the fasting post, I’d rather have a fantastic quality of life (which for me means plenty of lean mass, plenty of physical activity, and plenty of meat on my plate) than live a few extra, protein-restricted years.
I hope this proves helpful for your situation – though I’d hesitate to even classify it as a real “situation.” I wouldn’t worry.
How about everyone else? How much protein do you typically eat in a day? What’s your activity level like? Ever had any kidney problems?
Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.