The supposed dangers of protein are a popular subject.
Some say that a high protein intake can reduce calcium in bones, cause osteoporosis or even destroy your kidneys.
This article takes a look at whether there is 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 you must get through your diet, and 12 that are non-essential, which your body can produce from other organic molecules.
The quality of a protein source depends on its amino acid profile. The best dietary sources of protein contain all essential amino acids in ratios appropriate for humans.
In this regard, animal proteins are better than plant proteins. Given that the muscle tissues of animals are very similar to those of humans, this makes perfect sense.
The basic recommendations for protein intake are 0.36 grams of protein per pound of body weight (0.8 grams per kg) daily. This translates to 56 grams of protein for a 154-pound (70-kg) individual (1).
This meager intake may be enough to prevent downright protein deficiency. Yet, many scientists believe it’s not sufficient to optimize health and body composition.
For detailed information on how much protein you should get per day, check out this article.
Summary Protein is an essential macronutrient. Although the recommended daily intake may be enough to prevent deficiency, some scientists believe it’s insufficient to optimize health and body composition.
Some people believe that a high protein intake can contribute to osteoporosis.
The theory is that protein increases the acid load of your body, which then causes the body to take calcium out of the bones to neutralize the acid (4).
Even though there are some studies showing increased short-term calcium excretion, this effect does not persist over the long term (5).
In fact, longer-term studies do not support this idea. In one 9-week study, replacing carbohydrates with meat did not affect calcium excretion and improved some hormones known to promote bone health, like IGF-1 (6).
A review published in 2017 concluded that increased protein intake does not harm the bones. If anything, the evidence pointed to a higher protein intake improving bone health (7).
Multiple other studies show that a higher protein intake is a good thing when it comes to your bone health.
There are plenty of other potentially helpful nutritional strategies. If you want to learn more, check out this article on 10 natural ways to build healthy bones.
Summary Long-term studies show that a high protein intake may improve your bone health. It does not cause osteoporosis.
The kidneys are remarkable organs that filter waste compounds, excess nutrients and liquids out of the bloodstream, producing urine.
Some say that your kidneys need to work hard to clear the metabolites of protein from your body, leading to increased strain on the kidneys.
Adding some more protein to your diet may increase their workload a little, but this increase is quite insignificant compared to the immense amount of work your kidneys already do.
About 20% of the blood your heart pumps through your body goes to the kidneys. In an adult, the kidneys may filter around 48 gallons (180 liters) of blood every single day.
In conclusion, there is no evidence that a high protein intake harms kidney function in people who don’t have kidney disease.
Summary 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.
There are many benefits associated with a high protein intake.
- Muscle mass: Adequate amounts of protein have a positive effect on muscle mass and are crucial to prevent muscle loss on a calorie-restricted diet (20).
- Energy expenditure: Studies show that protein increases energy expenditure more than any other macronutrient (21, 22).
- Satiety: Protein keeps you full longer. Increased protein intake can lead to a decreased calorie intake and weight loss (23).
- Lower risk of obesity: Replacing carbs and fat with protein may protect you against obesity (24).
Overall, a higher protein intake is beneficial for your health, especially for maintaining muscle mass and losing weight.
Summary There are many benefits to a high protein intake, such as weight loss, increased lean mass and a lower risk of 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.
Exactly how much protein is harmful is unclear and likely varies between people.
One study in healthy, strength-training men showed that eating around 1.4 grams per pound of body weight (3 grams per kg) every day for a year didn’t have any adverse health effects (12).
Even eating 2 grams of protein per pound of body weight (4.4 grams per kg) for 2 months did not appear to cause any side effects (25).
But keep in mind that physically active people, especially strength athletes or bodybuilders, need more protein than less active individuals.
Summary Extremely high protein intake is unhealthy. It is unclear at what intake level protein becomes harmful. It likely depends on the individual.
At the end of the day, there is no evidence that eating protein in reasonably high amounts causes harm in healthy people. On the contrary, plenty of evidence suggests benefits.
However, if you have kidney disease, you should follow your doctor’s advice and limit your protein intake.
But for the majority of people, there is no reason to be concerned about the exact number of grams of protein in your diet.
If you follow a balanced diet that contains plenty of meat, fish, dairy or high-protein plant foods, your protein intake should be in a safe and healthy range.