One myth that seems hard to break is that eating a lot of protein is somehow bad for you.
It seems that our evolutionary heritage as meat eaters doesn’t matter, or the fact that our bodies are made with protein.
Why would evolution make us intolerant to something we’ve eaten for millions of years, and that our bodies are designed from?
Doesn’t make a lot of sense when you look at it that way, but this myth is still there, even touted by various professionals.
Let’s see if it’s true, or it’s just another myth of modern nutrition.
Is Eating Too Much Protein Bad For You?
There are two “concerns” that are prevalent about a high protein intake.
The first one, is that too much protein could be bad for the kidneys. The second one is that protein can lead to calcium loss from the bones, ultimately ending in osteoporosis.
Let’s see what the actual evidence has to say.
Do you know what the function of the kidneys is?
They “filter” the blood, removing toxins, electrolytes, fluid and various substances that the body doesn’t need anymore. When the filtered fluid that runs through the kidneys reaches the end, it is called urine.
The kidneys excrete the waste products of protein breakdown. Therefore, some like to argue that more protein adds more “stress” to the kidneys.
Here’s a newsflash: The kidney’s are always under stress. About 20% of the blood pumped by the heart goes directly to the kidneys, and they filter about 180L of blood every single day.
Adding a bit more protein to your diet might increase the workload of the kidneys, but it’s an incredibly small effect given the mind-blowing amount of work the kidneys carry out each day.
Really, this is what the kidneys are designed to do. And they’re damn good at it.
Well, enough with the ramblings. Let’s take a look at the evidence.
This large review article, published in 2004, looked at high-protein weight loss diets and discovered that there is no evidence to assume that there are any adverse effects of a high protein intake in healthy individuals (1).
They also note that bodybuilders, who have a much higher protein intake than the general population, tend to have healthy kidneys.
Another review article published in 2005, examining protein intake in healthy individuals, discovered that there is no evidence to assume that a high protein intake is detrimental to kidney health (2).
The funny thing here is that higher protein diets actually improve blood sugar control in type II diabetes (3, 4, 5) and reduce blood pressure (6, 7, 8), suggesting that a high protein diet should actually be protective against kidney disease.
If you already have kidney disease, then you may have a problem with protein and should talk to your doctor.
If you’re a generally healthy person then there doesn’t seem to be any reason to reduce protein, at least not for the sake of kidney health.
Another common belief is that a high protein intake acidifies your blood and “leeches” calcium from the bones.
It is true that some short-term studies have found that increased protein increases calcium excretion, but the fact remains that long-term studies show that a high protein intake actually leads to improved bone health.
The truth is, that a high protein intake shows a positive association with bone mass and bone density. The advice to restrict protein in order to protect your bones may be dangerous and actually have the exact opposite effect (9).
A study discovered that a low protein intake was associated with bone loss and fractures in elderly adults and there were no adverse effects noted in the individuals with the highest protein intake (10).
A large prospective study of postmenopausal women discovered that increased animal protein intake was associated with a lower risk of hip fracture (11).
The Functions of Dietary Protein
The body is in a constant state of flux. Most of our tissues are repeatedly broken down and rebuilt, every second of every day. This also applies to tissues like bone and muscle, and the protein in the diet is used to rebuild these tissues and sometimes to make even more of them (when gaining muscle, for example).
This also applies to organs, enzymes, hormones, receptors and various biomolecules that are made from protein. In order to replenish them, we need enough protein in the diet.
If you’re eating a low-carb diet, part of the protein you take in will be used to generate glucose for the tissues that need it (mainly the brain and red blood cells). Therefore, protein requirement may go up as carbs go down.
A High(er) Protein Intake is a Good Thing
Okay, now we know that the scare tactics against a high protein intake aren’t warranted, at least not when it comes to kidney and bone health.
What about other things? What about general health, body weight, etc?
Higher protein diets have a favourable effect on weight loss, leading to improved body composition and improved biomarkers of disease, most likely mediated by increased satiety and slightly elevated energy expenditure (16, 17, 18, 19, 20).
All in all, the evidence seems to suggest that a high protein intake is beneficial to humans, without any adverse effects despite the scare tactics.
Nothing to Worry About on a Real Food Based Diet
This seems to be another one of those cases where we would do best by listening to the conventional wisdom advice, then do the exact opposite.
If you eat a low-carb, real-food based diet with plenty of animal products then your diet will naturally be high in quality protein.
However, I don’t see any reason to supplement your diet with additional protein or amino acids, except maybe a bit of whey protein after a workout.
There is no reason to eat more than 30-40% of calories as protein, the rest should be from fat (and some carbs).
If you don’t have any medical problem, then I can’t see any reason not to embrace your higher protein diet, knowing that it is probably good for you despite the scare tactics by the pseudo-scientists.
Your bones will thank you, your body weight will improve, you will be less hungry and given that high protein reduces diabetes and blood pressure then your kidneys may even thank you as well.