When we think of protein, for many people the first thing that comes to mind is body builders or athletes. But did you know that protein is integral for optimal body functioning?
What is protein?
Protein is a macronutrient that consists of chains of small building blocks known as ‘amino acids’.
Why do we need protein?
Protein is essential for many important bodily processes including:
Growth and maintenance (as building blocks)
Digestion (as enzymes)
The production of some hormones such as insulin (regulation of blood glucose) and human growth hormone (promotion of growth)
Immunity (forms the structure of antibodies)
Fluid and electrolyte balance (maintenance of fluid in the body tissues)
Transportation of substances (such as fats, vitamins, minerals and oxygen) around the body
Energy (when carbohydrate or fat intake is insufficient, protein is sacrificed)
What is an amino acid?
All amino acids are assigned the same basic structure – a central carbon atom, surrounded by an attached hydrogen group, amino group and an acid group. A fourth attachment which distinguishes each amino acid from the others is the side group. This side group is unique amongst 20 different amino acids which are utilised by the body to build protein.
Identification of amino acids
All amino acids play a role in in the maintenance of health in the body. Amino acids are identified as either ‘essential’ or ’non-essential’.
Non-essential amino acids
Refer to amino acids the body can synthesize itself from the raw materials of nitrogen, carbohydrates and fat
Essential amino acids
Refer to amino acids that the body cannot synthesize itself, therefore they must be sourced from the diet particularly from protein-rich sources
Conditionally essential amino acids
There are some variations in amino acids that are required during certain life stages
Histidine is required during childhood in order to achieve optimal growth
In adults, there is evidence that histidine is only required after 7weeks without consumption
No protein stays in our bodies for the entire duration of our lives. In fact, protein is constantly being broken down and replaced through a dynamic process known as ‘protein turnover’. This process utilises a lot of energy, accounting for approximately 15-20% of the energy we expend at rest. Our bodies are very efficient at rebuilding protein, as long as we are getting good sources of dietary protein.
Dietary Sources of Protein
Protein is obtained from:
- Animal sources:
- Plant sources:
The quality of protein
A good quality protein contains all essential amino acids, and may/may not include non-essential amino acids. Building protein cannot be achieved when the source of protein is low in an essential amino acid. Whilst the liver has the ability to synthesise non-essential amino acids as required, if an essential amino acid is missing, in order to obtain it, the cell must dismantle its own protein structure. When this happens, protein breakdown occurs.
Consumption of complete proteins, which contain all essential amino acids, is integral for protein’s functions. Complete proteins are found in all animal products except for gelatin, which lacks tryptophan and therefore cannot be relied upon as the only source of protein. In terms of vegetarian/vegan options, the good sources of complete protein are soybeans, pumpkin seeds, spirulina, hempseeds, buckwheat, and quinoa.
Other plant-based ways of getting good quality protein is by protein combining. This involves combining different plant-protein foods that have opposing amino acid patterns. As a result, a meal is yielded where all the essential amino acids are present, therefore providing a complete protein source.
Combining incomplete proteins
Recommended Daily Protein Intake
The Better Health Channel advises that “as a rough guide, the recommended dietary intake (RDI) for protein (measured in grams per kilogram of bodyweight) is:
0.75 g/kg for adult women
0.84 g/kg for adult men
Around 1 g/kg for pregnant and breastfeeding women, and for men and women over 70 years.”
Evidence also states that these RDIs provide an adequate amount of protein for body builders and athletes. Following high protein diets can be harmful. Always consult an appropriate healthcare professional prior to starting any high protein diet.
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