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Protein

Protein is a source of energy but its main role in the body is growth and repair. Protein is a building block- 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 found in both animal and plant foods.

  • Animal sources: meat, fish, chicken, eggs, milk, cheese and yoghurt.
  • Plant sources: soy protein (such as soybeans, tofu and soy milk), grains (quinoa, oats, barley, etc), nuts and pulses (dried beans, peas and lentils).

Protein is made up of 20 amino acids. While all 20 of these are important for your health, 9 are classified as essential and 11 as non-essential.

  • Essential amino acids cannot be made by the body and thus must come from food
  • Non-essential amino acids can be made by our body

All animal foods, as well as soybeans (a plant-based source of protein), provide all 9 essential amino acids in sufficient quantities and are classified as complete proteins. All other plant-based sources of protein lack one or more of the essential amino acids and are called incomplete proteins. People who follow a plant-based diet should eat a variety of plant sources of protein every day (e.g. legumes, nuts, seeds, whole grains) to get all the essential amino acids.

How much do we need to eat?

 Age (years)RDI Protein (grams/day)
Infants/Toddlers1-314
Children4-820
Boys9-1340
14-1865
Girls9-13
35
14-1845
Men19-7064
>7081
Women19-7046
>7057
Pregnancy60
Breastfeeding

67

These values are taken from Protein | Nutrient Reference Values for Australia and New Zealand. 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.

Do New Zealanders get enough protein?

Most of us easily meet (and surpass) the RDI for protein. Even vegans and vegetarians who eat a relatively balanced diet can easily get enough protein in their diet. In saying that, a lot of us don’t distribute protein well throughout the day- we tend to eat little at breakfast, a bit more at lunch and then a significant amount at dinner time. Ideally, we should focus on having a good serving of protein at each meal. This helps keep hunger at bay (as protein makes you feel full) and helps muscle growth/retention (Paddon-Jones et al., 2008).

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: 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.
  • Gym goers/active people: Similar to athletes, gym-goers and active folk (e.g. recreational sports players) will require more protein to support muscle gain and function.
  • Older adults – The increased protein recommendation for older age groups counters the age-associated loss of muscle mass and overall body protein stores. Eating more protein as we age can reduce the risk of falls, frailty and infection.

Protein content of foods

Food ItemProtein (g)
1 grilled lean beef fillet steak (135g)38.2
1 grilled chicken breast (107g)33.4
1/2 baked fillet Hoki (122g)26.8
1 can tuna in spring water (100g)25.3
1 grilled pork leg steak (80g)19.3
1/4 can boiled red kidney beans (100g)7.9
Tofu (100g)8.1
1 cup trim milk (250ml)10.1
1 boiled egg (50g)6
1 pottle plain, low fat yoghurt (150g)7.2
1/4 can baked beans in tomato sauce (100g)5
1 slice white bread (40g)3.1
10 almonds (12g)2.5
2cm cube Edam cheese (8g)2.2

Does protein help with weight loss?

Protein helps to make you feel full after eating, so including 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).

Last reviewed: 02/02/2022

Last modified: March 29, 2022