If you have ever dipped your toe into the expansive world of fitness then you will no doubt have heard a lot about the importance of protein in the diet. Although protein needs do become more complex if you are trying to enhance your fitness levels, it is also an aspect of overall nutrition that everybody should pay attention to.

Protein has three main functions within the body:

  • Growth and Repair
  • Physiological Function
  • Energy

Let’s take a closer look at these three essential functions.

Growth and Repair

All of the tissue within the body is in need of maintenance and repair in a continuous way. Protein is a key component of this and it forms a part of every living cell in the body.

Physiological Function

Protein contributes to a huge range of physiological functions. All of the enzymes inside of the body are made up of protein. Enzymes are substances that bring about necessary chemical reactions, such as energy production and the digestion of food.

Certain hormones are made of protein, and without these hormones the body would be unable to function as it does. Furthermore, antibodies produced by white blood cells that are key to fighting infection are also made up of protein.


Protein is not considered to be a primary source of energy, and the body will utilise carbohydrates and fat before it calls upon protein sources to help. However, when in use, protein will provide 4 Kcals of energy per gram.

What is Protein?

To understand the role that protein plays in the body, it is of course helpful to know what protein is.

Proteins are made up of amino acids, of which there are 20. Eight of these amino acids are considered to be essential amino acids. This means that the body is not able to produce them on its own, and that they therefore must be obtained through dietary sources. Amino acids are mainly found in animal sources, but it is actually possible to consume all of them from an entirely plant-based diet.

If a protein source has one or more of the essential amino acids missing then it is considered to be an incomplete protein. Although different plant-based proteins are often missing one or more essential amino acids, it is still possible to combine different sources to obtain all eight in the diet.

If you are following a plant-based, vegetarian, or vegan diet, then it is a good idea to include a range of pulses, grains, nuts and seeds regularly to ensure you meet your amino acid quota!

The eight essential amino acids are:

  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine

There are 12 non-essential amino acids. The body can easily make non-essential amino acids itself, but they are also commonly found in non-animal food sources.

The 12 non-essential amino acids are:

  • Alanine
  • Arginine
  • Asparagine
  • Aspartic acid
  • Cysteine
  • Glutamic acid
  • Glutamine
  • Glycine
  • Histidine
  • Proline
  • Serine
  • Tyrosine

The quality of a protein source is generally determined by two factors. Those are how easily digestible the protein is, and the amino acid content of the protein in question.

Protein Requirements

The protein requirements of the general population will usually be approximately 0.8 grams of protein per each kilogram of body weight per day. This should account for between 10 and 15% of total calorie intake for the day,

This means that if a person weighs 60kg then they should aim to consume 48 grams of protein per day.

Those who lead a more active lifestyle and participate in endurance training, such as athletes, will require an increased amount of protein in the diet.

This is firstly because they will need additional help repairing muscle tissue once it is broken down. This is due to depleted glycogen stores. This begins to happen after approximately 90 minutes of endurance training. Additionally, extra protein will be required for general growth and repair of the muscles due the extra strain placed on the body during endurance training.

People in this category should aim to consume approximately 1.2 grams of protein per each kilogram of body weight per day.

This means that if a person weighs 60kg then they should aim to consume 72 grams of protein per day.

People who regularly engage in strength training, such as weight lifters, will need to consume even more protein than endurance athletes if they are to maintain and develop their bodies.

Generally people in this category should aim to consume 1.8 grams of protein per each kilogram of body weight per day.

This means that if a person weighs 60kg then they should aim to consume 108 grams of protein per day.

Sources of Protein

Check back soon for some fantastic advice on the best foods to eat to meet your protein quota each day! 


1) https://www.nutrition.org.uk/nutritionscience/nutrients-food-and-ingredients/protein.html