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Protein is a source of energy but its main role in the body is growth and repair. It helps in the formation of muscles, hair, nails, skin and organs, such as the heart, kidneys and liver. We all contain a significant amount of protein. For example, a 76kg man is made up of 12kg of protein (16%).
Which foods contain protein?
Protein is made up of 20 amino acids, some of which our body can make and others we have to obtain from food. Protein is found in both animal and plant foods.
- Animal sources: meat, fish, chicken, eggs, milk, cheese and yoghurt.
- Plant sources: soy protein (such as soy beans, tofu and soy milk), grains (quinoa, oats, barley, etc), nuts and pulses (dried beans, peas and lentils).
All animal foods, as well as two plant sources -soy protein and quinoa - provide all the necessary amino acids required by the body for good health and these are called essential amino acids. All other plant-based sources of protein lack one or more of the amino acids we need to obtain from our food. People who do not eat any animal products (vegans) should include a variety of plant sources of protein every day to ensure they obtain all the essential amino acids.
How much do we need to eat?
RDI Protein (grams/day)
The following examples show how daily protein requirements can be met:
- An 18yr old girl can meet her required 45g by eating grilled chicken breast, 2 slices of wholemeal bread and a pottle of yoghurt.
- A 50 year old man can meet his required 64g by eating: baked beans on two slices of multigrain toast, and a grilled steak.
Groups with increased protein requirements
- Growing teenagers during their adolescent growth spurt protein needs are high to cover both energy requirements and support the growing body.
- Pregnant and breastfeeding women - protein requirements are increased to support the changes in the mother and foetal growth.
- People with illnesses (such as cancer) and injuries - as protein aids the repair of body tissue, and keeps our immune systems healthy. When your body doesn’t get enough protein, it might break down muscle for the fuel it needs. This makes it take longer to recover from illness and can lower resistance to infection.
- Athletes and the very active - Endurance athletes in heavy training require extra protein to cover a small proportion of the energy costs of their training and to assist in the repair and recovery process after exercise. Strength athletes, who are interested in gaining muscle size and function, require more protein in the early stages of very intensive resistance exercise.
Protein content of foods
1 grilled lean beef fillet steak (135g)
1 grilled chicken breast (107g)
1/2 baked fillet Hoki (122g)
1 can tuna in spring water (100g)
1 grilled pork leg steak (80g)
1/4 can boiled red kidney beans (100g)
1 cup trim milk (250ml)
1 boiled egg (50g)
1 pottle plain, low fat yoghurt (150g)
1/4 can baked beans in tomato sauce (100g)
1 slice multigrain bread (45g)
1 slice white bread (40g)
10 almonds (12g)
2cm cube Edam cheese (8g)
Does protein help with weight loss?
Protein helps to make you feel full after eating, so including a protein-rich food at each meal can help those people who are trying to lose or maintain their weight.
However, excessively high protein diets are not recommended, especially those omitting other food groups, such as grains or vegetables and fruit. Weight gain is a result of the energy taken in being more than the energy burnt off through metabolism or activity, irrespective of the source of the energy (kilojoules/calories).