Protein is a nutrient in the foods that we eat that provides our bodies with the building blocks (amino acids) for body structure like our bone, muscle, blood vessels, and skin.
For example, amino acids like glycine, proline, and arginine are needed to build collagen - the main structural protein in the body.
Collagen is like “glue” holding things together, making body structure strong and able to stretch, and is a major component of our bone, muscles, tendons, cartilage, and skin.
But body structure is not the only reason we need to consume protein in our diets each day.
Dietary proteins also provide our bodies with the amino acid building blocks to produce chemical messengers, like hormones, so that communication occurs. For example, amino acids like leucine, isoleucine, and valine, are needed in the synthesis of insulin, the main hormone in blood sugar regulation, and these are provided through the foods we eat (1).
In fact, without dietary proteins, the body would be unable to produce enzymes that act as catalysts in all chemical reactions, and life would end!
As you can see, consuming protein each day is important for a healthy life – so, how much protein is needed for all this structure and activity…that’s where things get a bit more complex.
Whole foods contain proteins, but not all foods contain complete proteins.
A complete protein provides all of the essential amino acids, of which there are nine (2).
An essential amino acid is one that the body cannot produce and so must be consumed in the diet (2).
Animal protein, like meat, eggs, fish, and dairy, supply the body with complete proteins. Most plants are a source of incomplete protein, but there are exceptions such as quinoa (3).
How much protein should we be consuming each day?
The amount of protein needed is variable and dependant upon the individual and their lifestyle.
The general rule of thumb for a healthy adult with little physical activity is about 0.8 grams of protein per kg of body weight per day (4).
So, based on this rule of thumb a 170 pound (77.1 kg) adult would consume about 61.7 grams of protein each day.
Consuming 2 eggs (12 grams), and a glass of milk (8 grams) at breakfast, 1 cup of bean chili (20 grams) at lunch, and about 3.5 ounces of chicken (24.5 grams) at dinner would provide more than the general daily protein requirement of 61.7 grams for the 170-pound individual referenced above (5).
Some, however, need more protein each day. Those that strength train may require about 1.2 grams of protein per kilogram of body weight each day, and those who perform long-duration endurance activities may require up to 1.5 grams per kilogram of body weight/day (6).
Can we consume too much dietary protein?
Just as we can consume too little protein for a healthy body, we can also consume too much.
Consuming more protein than the body requires may be harmful to bones, as well as the liver and kidneys (7).
Too much protein in the diet can make the body more acidic which taxes the liver and can lead to complications like calcium imbalances, and bone loss (7) (8). The kidneys must work harder to excrete the excess acid from the body and excess urinary calcium excretion can lead to the formation of kidney stones (7).
In addition, the biological value of dietary protein, or the amount that can be transformed into body proteins, depends upon the relative amount and composition of the essential amino acids contained in the protein (6).
Signs that you may be consuming too much dietary protein
Constipation can occur with high protein diets if the diet is also deficient in water and plants that provide fiber. Excess protein intake with too little water and little to no fiber can back up the intestines which can then lead to further health complications (9).
Eating too much protein can cause chronic bad breath (halitosis) which is mainly the result of bacterial breakdown of protein on the tongue (10).
Gastrointestinal issues like abdominal pain can be associated with excess protein consumption (11).
Most healthy individuals can obtain their daily protein needs through the foods that they consume when protein is made a part of a balanced whole food diet.