What is protein? | The nutrition guide

It's often idolised, with many people worrying about not getting enough. And it's essential for our health. But what exactly is protein?

What is protein? | The nutrition guide

Our bodies are brimming with metabolic processes. They're home to numerous cellular transformations. From our hair to our nails, skin, hormones and muscles, our bodies are constantly renewing themselves, every single day, to keep us alive and keep us active. And these processes can't happen without fuel and building materials. Which is where proteins come into play!

What is protein? What is it for and how is it used in our bodies? What are the different types of protein? We answer all your questions!

A quick recap of macronutrients

A so-called balanced diet means eating foods that are rich in:
Macronutrients: protein, carbohydrates, fats;
Micronutrients: vitamins, minerals and trace elements.

To work correctly and stay healthy, the body needs all of these elements in the right quantity - as well as of the right quality. For example, processed foods don't fully meet our physiological needs.
In this article, we're looking at protein, but you might also want to check out our features on carbohydrates and fats.

What is a protein?

A protein is a large molecule composed of polypeptides, which themselves are composed of amino acids.
If we take a closer look, a protein is like a necklace made up of 20 pearls: the 20 amino acids.
The way these amino acids are organised is determined by our genetics (our DNA). In other words, genetics decide whether the red pearl comes before the yellow one.
Each necklace is unique, because each individual is unique. So we all have proteins that are specific to each of us.
Protein accounts for less than 20% of our total body mass. That's all! 

What is protein for?

Protein is essential because it's used for growing tissue, building muscle mass, and repairing muscle fibres that have been damaged by physical activity or injury.

It has a limited, variable life expectancy, which is affected by our lifestyles and activities. We therefore need a daily intake of protein and amino acids to replace what's already in our bodies.
Proteins, and specifically the amino acids they're made from, play several vital roles.

Structural and functional role

Protein is involved in numerous regeneration processes in our tissues: muscle fibres, bones, tendons, skin, nails, hormone receptors, antibodies (the immune system), enzymes (such as digestive enzymes), and more.
Proteins are the building blocks of our bodies.
In other words, the building and repair work involved in many biological functions is done by proteins and their amino acids.

Providing energy

From a metabolism point of view, protein provides 4 kcal of energy per gram of protein.
It therefore acts as a fuel to keep our bodies moving - just like carbohydrates and fats.
However, this role as a fuel isn't protein's main purpose. During a physical activity or an exam, for example, carbohydrates are used as the main energy source, followed by fats.

The different types of protein

Complete versus incomplete proteins

Proteins are composed of 20 amino acids.
But not every necklace has every pearl on it. In this case, we say that the protein is "incomplete" because it doesn't provide the body with all of the amino acids.
When the necklace has 20 pearls (all 20 amino acids), we describe it as "complete".

Some of these amino acids are referred to as "essential" because the body can't produce them itself. We need to eat them, in the right quantity and each day, as part of our diets. Take a look at our dedicated article on amino acids to find out more about their essential role.

Animal versus plant protein

The essential amino acids are present in all animal protein, which makes meat an easy source of protein.
As for plant protein, most aren't complete proteins. To give our bodies all of the essential amino acids that they need, it's important to combine several types of plant protein (except in the case of quinoa, which is a complete plant protein). It's therefore a bit trickier to eat the right protein with a plant-based diet. That said, vegetables are also great for providing carbohydrates, fats and micronutrients. There's no reason to go without them. Au contraire!

Where can you find protein?

It's all about our diets!
During digestion, protein is split up by proteases (the enzymes that digest protein) into amino acids: the necklace will be broken so that the body can more easily access each pearl.
The amino acids that we've eaten are then stored and used as needed to replace tissue fibres, repair our muscles, and perform the other functions mentioned earlier.
It's therefore vital that our diets contain all the protein we need, specifically the essential amino acids. Check out our article on protein-rich foods to make sure you get the right protein dose!

In a nutshell, protein is found in all sorts of foods: dairy products, meat, fish and seafood, cereals, legumes and even nuts and seeds.

Dietary supplements

To make sure they're getting enough protein and all of the amino acids they need for their muscles to recover, some athletes use dietary supplements. These supplements often come in the form of powders and are used to make protein drinks that speed up the repair of muscle tissue that has been damaged by training.
But they're not at all essential, so long as you're eating enough protein anyway, and so long as the protein you eat is varied enough. Particularly if you're not a professional athlete!

To give you an idea of the numbers, the daily protein needs of a non-sedentary but not-particularly-sporty person are around 1 g per kg of bodyweight per day. In very active people who want to increase their muscle mass, this is more like 2 g or even 2.5 g per kg of bodyweight per day.

Don't worry: protein deficiency in industrialised countries is extremely rare!

You now know all about protein. It's essential for maintaining the structure and foundations of our bodies, and must be a part of our diets. On the other hand, we mustn't neglect carbohydrates and fats because it's the right quantity of these three macronutrients and of micronutrients that keeps our diets healthy and balanced.

What is protein? | The nutrition guide


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