Salmon, eggs and vegetables on a table

Protein

Protein is a nutritional term many of us are familiar with, and is often associated with meat consumption and muscle building. However, protein is a nutrient that’s contained in all animal and plant-based foods, and is an essential part of a healthy diet.

What is protein?

Protein is found in all living cells (animal and plant) and has functional and structural properties. Proteins are made up of 20 amino acids. Some amino acids can be made by the body, however there are 9 amino acids (known as essential amino acids) that need to be obtained by the food and drinks we consume.

The major food and drink sources of protein are meat, poultry, fish, grains, grain-based foods, dairy foods and vegetables. Amino acids are easily consumed through animal-based foods, although all necessary amino acids can be obtained from plant-based foods also. If you’re following a vegetarian diet you will need to eat a wide variety of plant-based foods to help you meet all your nutritional requirements. For those eating a vegan diet, supplementation of B12 is also recommended as vitamin B12 is found mostly in animal-based foods.

Why do our bodies need protein?

The structure of protein will influence how it is used in our body, how it is digested and how it interacts with other substances. The body uses protein for muscle repair and growth, it is also used in our blood, skin, hair and nails. Protein can also sometimes be used as an energy source for the body.

What are the recommendations for protein intake?

The amount of protein your body requires depends on several factors, including weight, age and health, and can also vary during stages of body growth and maintenance.

The daily recommended dietary intake (RDI) for protein (in g/kg bodyweight) is:

  • 75g/kg for adult women
  • 84g/kg for adult men
  • 1g/kg for pregnant women and 1.1g/kg for women who are breastfeeding
  • approximately 1g/kg for people over 70 years
  • the needs of children and adolescents vary according to their age and weight

What happens if we consume too much or too little protein?

Most Australians eat a lot more protein than they actually need. When protein is broken down, it produces ammonia as a by-product, which is extremely dangerous to the body so it is converted to urea and eliminated through the kidneys in urine. The more protein eaten each day, in excess of bodily needs, the more the kidneys need to work to get rid of the ammonia. There is insufficient data to set upper level of intakes of protein, but caution is needed when exceeding protein intake, especially with use of protein, vitamin and mineral supplements.

In severe disease states or fasting, substantial body protein losses may result as the body uses protein for energy. As protein is necessary to the functioning of the body, serious protein depletion can be life threatening.