The "dangers" of protein are a persistent myth.
Some say that a high protein intake can "leach" calcium from bones and cause osteoporosis, or that protein can destroy your kidneys.
However, there really isn't any evidence to support these claims.
Proteins are the building blocks of life and every living cell uses them for both structural and functional purposes.
They are long chains of amino acids linked together like beads on a string, then folded into complex shapes.
There are 9 essential amino acids that we must get from the diet and 12 that are non-essential, which the body can produce out of other organic molecules.
The quality of a protein source depends on its amino acid profile. The best sources of protein in the diet contain all the essential amino acids in ratios that are appropriate for humans.
In this regard, animal proteins are better than plant proteins, which makes perfect sense given that the muscle tissues of animals are very similar to our own tissues.
The health authorities recommend an intake of 56 grams per day for men and 46 grams per day for women, varying between individuals based on age, body weight, activity levels and some other factors ().
While this meager intake may be enough to prevent downright deficiency, it is not in any way sufficient to optimize health and body composition. People who are physically active or lift weights are going to need a lot more than that.
Bottom Line: Protein is an essential macronutrient. Even though the generally recommended intake may be enough to prevent deficiency, it is insufficient to optimize health and body composition.
It is commonly believed that a high protein intake can contribute to osteoporosis.
The theory is that the protein increases the acid load of your body, which then causes the body to take calcium out of the bones to neutralize the acid.
Even though there are some studies showing increased calcium excretion in the short term, this effect does not persist over the long term.
In fact, longer term studies do not support this idea at all. In one 9 week study, replacing carbohydrate with meat did not affect calcium excretion and improved some hormones known to promote bone health, like IGF-1 ().
A review published in in 2011 concluded that there is no evidence that increased protein harms the bones. If anything, the evidence points to a higher protein intake improving bone health, NOT the other way around ().
There are multiple other studies and papers showing that a higher protein intake is a good thing when it comes to bone health.
For example, it improves bone density and lowers the risk of fracture. It also increases IGF-1 and lean mass, both known to promote bone health (, , , , ).
The whole protein-osteoporosis thing is a myth with literally zero evidence to back it up. This is one example of where blindly following conventional nutritional wisdom leads to the exact opposite result of what you expected.
Bottom Line: Despite a high protein intake increasing calcium excretion in the short term, long term studies show a strong positive effect on bone health.
The kidneys are a remarkable organ that filters unneeded substances and liquids out of the bloodstream, producing urine.
Some say that the kidneys need to work hard to clear the metabolites of protein from the body, leading to increased strain on the kidneys.
Well, I have a newsflash for these people. The kidneys are always under stress. That's what they're made for.
About 20% of the blood pumped by the heart goes to the kidneys and they filter a total of 180 liters (48 gallons) of blood, every single day.
Adding some more protein to your diet may increase their workload a little, but it is really insignificant compared to the immense amount of work that they do already.
I looked into the literature and even though there is evidence that high protein causes harm in people with diagnosed kidney disease (, ), the same does NOT apply to people with healthy kidneys.
In fact, there are no studies showing harmful effects of protein in people who don't have kidney disease. Even bodybuilders have healthy kidneys and they tend to eat very large amounts of protein, both from food and supplements (, ).
The two main risk factors for kidney failure are high blood pressure (hypertension) and diabetes. A higher protein intake improves both (, , , ).
So even IF the increased protein has a harmful effect on the kidneys (which there is no evidence of), it appears to be outweighed by the beneficial effects of lowered blood pressure and blood sugar.
Bottom Line: A high protein intake has been shown to accelerate kidney damage in people who have kidney disease. However, higher protein diets don't adversely affect kidney function in healthy people.
I'd like to point out that there are many benefits to eating more (not less) protein.
- Muscle mass: Adequate protein has a positive effect on muscle mass and is crucial to prevent muscle loss on a calorie restricted diet (, , ).
- Energy expenditure: Studies show that protein increases energy expenditure the most out of all the macronutrients (, ).
- Satiety: Protein is very satiating and increasing protein can lead to a decreased calorie intake and weight loss ().
- Lower risk of disease: Increased protein intake can be protective against diseases like diabetes and obesity (, ).
Overall, higher protein is a good thing and the amounts commonly recommended by the health authorities are too low!
Bottom Line: There are many benefits to a high protein intake, such as weight loss, increased lean mass and a lower risk of diseases like diabetes and obesity.
The body is in a constant state of flux, constantly breaking down and rebuilding its own tissues.
Under certain circumstances, our need for protein can increase. This includes periods of sickness or increased physical activity.
We need to consume enough protein for these processes to occur.
However, if we eat more than we need, the excess protein will be broken down and used for energy.
Even though a relatively high protein intake is healthy and safe, eating massive amounts of protein is unnatural and may cause harm. Traditional populations got most of their calories from fat or carbs, not protein.
Although I don't know of any study that demonstrates exactly when it becomes harmful, I'd say that 1 gram of protein per pound of body weight (2.2 grams per kg) or 30-40% of calories should be safe, but going beyond that is uncharted territory.
I personally eat about 100-150 grams of protein per day, but on workout days I eat about 200 grams because I like to have some whey protein right after my workouts.
Keep in mind that athletes need more protein than sedentary individuals, especially strength athletes or bodybuilders.
In my opinion, the idea that protein is harmful to humans is one of the more ridiculous myths out there.
Our species evolved as meat eaters, not to mention the fact that we're literally made of meat.
How could something we're made of be bad for us? It just doesn't make sense.
At the end of the day, there is no evidence that a high protein intake causes harm and plenty of evidence showing benefits. If you have healthy kidneys, then it's probably best to err on the side of a higher protein intake, rather than lower.
For the majority of people, there is no reason to be concerned about the exact number of grams of protein in the diet.
If you eat healthy, unprocessed animal foods every day, then your protein intake should automatically land in a safe and healthy range.